Sorry -- I've been away from home on business while the latest flack occurred under the general topic heading "Galileo interference on L band".
First off, just so everyone can read the presentation materials that we used during the San Diego meeting, please take a look at the EaglePedia web site at http://www.amsat.org/amsat-new/eagle/EaglePedia/index.php/San_Diego_Digital_.... Then take a look at my presentation "Frequency Considerations for Eagle" at http://www.amsat.org/amsat-new/eagle/EaglePedia/uploads/1/19/Microwave_Freq_.... You will see (my slide 6) that I present the arguments pro/con about why (IMHO) L-band is at jeopardy as a long-term uplink band.
Let me add a few comments about why I'm so concerned. The reason that the Galileo E6 (functionally the same as GPS L2, and overlaying the amateur 1260-70 MHz uplink allocation) is important for some uses is that it, when used in combination with the primary 1.57± GHz "L1" frequency (which is what all your cheap hand-held GPS receivers use), can be used to correct the ionospheric errors; the ionosphere adds upwards of 10 meters to the pseudo-range for each GPS satellite. Because of geometric factors (expressed quantitatively in VDOP), this can in turn yield errors in height of up to about 30 meters. [The WAAS and EGNOS signals provide some correction for these biases to the few meter level, but cannot be relied on during severe ionospheric storms.]
There is a lot of factual evidence that when dual-frequency geodetic GPS receivers (costing ~$25,000 -- hardly cheap!) have been used in proximity to terrestrial amateur L-band stations, the GPS performance is seriously degraded. I direct your attention to several reports on the topic:
* Must reading -- GPS/GLONASS vs L-band digipeaters (Also see GPS World, Oct.2002) (warning contains numbers and equations, as well as uncomplimentary comments about digipeaters) http://elib.uni-stuttgart.de/opus/volltexte/1999/278/pdf/278.pdf#search=%22g... * Amateur and Radar QRM reported at a 1999 technical meeting: http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/33rdmeeting/Presentati... * A tutorial that shows how interfering signals can affect a spread spectrum GPS rcvr (caution -- contains more numbers): http://www.rin.org.uk/SITE/UPLOAD/DOCUMENT/Vuln-Owen.pdf#search=%22gps%20ama...
Even though US amateurs may feel that Galileo is a "European only" problem, read carefully Rick's (W2GPS) comments -- in his real life for many years he was a VP with ARINC (the people who worry about standards in the airline industry) and was on many FAA and ICAO committees that decide on airline safety.
Also realize that the Europeans are absolutely determined to develop their own GNSS (Global Navigation Satellite System) call Galileo -- in part because they don't really trust a system that depends on the US Military, and in part because they see a giga-Euro business opportunity for the EC. Who knows how long it will survive, but the Russians have their competing GLONASS system. And both the Chinese and Japanese see that they need to enter into the GNSS race is they are to be world-class technical competitors.
We, the Eagle technical team, have never said that L-band won't work NOW or 5 years from now. But our vision for Eagle is that when the first one flies 4-5 years from now, we want it to be a useful resource for at least a 10 year lifetime. We are very concerned about making a several million dollar (after you count the volunteer builder's blood, sweat & tears) investment only to have it blown away right after launch by the GNSS cartels just because we picked L-band to be anything like a "primary" uplink.
73, Tom
Tom Clark, K3IO wrote:
Let me add a few comments about why I'm so concerned. The reason that the Galileo E6 (functionally the same as GPS L2, and overlaying the amateur 1260-70 MHz uplink allocation) is important for some uses is that it, when used in combination with the primary 1.57± GHz "L1" frequency (which is what all your cheap hand-held GPS receivers use), can be used to correct the ionospheric errors; the ionosphere adds upwards of 10 meters to the pseudo-range for each GPS satellite. Because of geometric factors (expressed quantitatively in VDOP), this can in turn yield errors in height of up to about 30 meters. [The WAAS and EGNOS signals provide some correction for these biases to the few meter level, but cannot be relied on during severe ionospheric storms.]
Dr. Clark,
There are several issues at play here.
First off, the Galileo E6 is currently specified to serve "Commercial Services" and "Public Regulated Service". Several messages in this thread have discussed "Safety of Life" concerns. E6, as currently publicly stated, will not be used for aircraft navigation. Thus, "Safety of Life" does not come into play when discussing the impacts amateur transmissions may have on E6 users. Amateur transmissions MAY impact commercial and public regulated services, however, the Galileo consortium emphasizes that provisions are being made to mitigate intentional and unintentional interference to these users.
For Galileo users, ionospheric error corrections can be made using E5 and E2/E1 (basically L1) signals. If memory serves me, the greater frequency spread between E5 and E2/E1 should provide slightly more accurate ionospheric error corrections than would be achieved using either E2/E1 and E6 or E5 and E6.
There is a lot of factual evidence that when dual-frequency geodetic GPS receivers (costing ~$25,000 -- hardly cheap!) have been used in proximity to terrestrial amateur L-band stations, the GPS performance is seriously degraded. I direct your attention to several reports on the topic:
* Must reading -- GPS/GLONASS vs L-band digipeaters (Also see GPS World, Oct.2002) (warning contains numbers and equations, as well as uncomplimentary comments about digipeaters) http://elib.uni-stuttgart.de/opus/volltexte/1999/278/pdf/278.pdf#search=%22gps%20interference%20%20digipeater%22 * Amateur and Radar QRM reported at a 1999 technical meeting: http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/33rdmeeting/Presentations/Weber.ppt * A tutorial that shows how interfering signals can affect a spread spectrum GPS rcvr (caution -- contains more numbers): http://www.rin.org.uk/SITE/UPLOAD/DOCUMENT/Vuln-Owen.pdf#search=%22gps%20amateur%20interference%22
I know very well, first hand, the susceptibility of GPS to unintentional and intentional interference. No arguments there. There is a lot of on-going work in both the military and commercial sectors to mitigate this vulnerability. An example of this is the much more robust waveform L5 will employ as well as higher downlink power levels (as both future GPS and Galileo satellites will employ). There are other technologies at play too. However, the unintentional sources of interference are not just limited to 'problems' caused by the amateur radio community. There was a documented real-world case of a faulty Radio Shack TV antenna amplifier on some pleasure craft in the L.A. area (if memory serves me again) taking out L1 over a wide area in the mid 90's. We won't even talk about the intentional, real-world, threats that are out there. GPS interference mitigation is big business and technology for both the military and commercial sectors will be greatly improved as time marches on.
The amateur radio cases cited in the above references appear to all be high duty cycle emitters with radiation patterns generally aimed at the horizon. I doubt our earth to space uplinks would have the same duty cycles and most of the intentional radiation will be directed above the horizon. This reduces the probability of unintentional interference to GPS, Galileo, and other future systems.
Even though US amateurs may feel that Galileo is a "European only" problem, read carefully Rick's (W2GPS) comments -- in his real life for many years he was a VP with ARINC (the people who worry about standards in the airline industry) and was on many FAA and ICAO committees that decide on airline safety.
Not all US amateurs feel this way. All one has to do is look at the years of effort spent in negotiations between the US and Europeans over Galileo-GPS compatibility issues and spectrum reutilization. That's why E5 and E1/E2 can overlap the GPS L2 and L1 allocations.
Again, from an airline perspective, I will argue there are far more critical threats to GPS/Galileo signal integrity than amateur radio which have to and are being addressed. These threats cannot be regulated or controlled as we amateurs are.
Also realize that the Europeans are absolutely determined to develop their own GNSS (Global Navigation Satellite System) call Galileo -- in part because they don't really trust a system that depends on the US Military, and in part because they see a giga-Euro business opportunity for the EC. Who knows how long it will survive, but the Russians have their competing GLONASS system. And both the Chinese and Japanese see that they need to enter into the GNSS race is they are to be world-class technical competitors.
And it will be interesting to see how this all plays out.
We, the Eagle technical team, have never said that L-band won't work NOW or 5 years from now. But our vision for Eagle is that when the first one flies 4-5 years from now, we want it to be a useful resource for at least a 10 year lifetime. We are very concerned about making a several million dollar (after you count the volunteer builder's blood, sweat & tears) investment only to have it blown away right after launch by the GNSS cartels just because we picked L-band to be anything like a "primary" uplink.
The same concerns could be expressed about ANY of the uplink or downlinks that are planned. ANY of them could be taken away at any time. Spectrum auctions are a wonderful cash cow to Uncle Sam and who knows what special interest groups our elected officials will cater to in the future. However, one thing is historically proven...that if we do not use our amateur allocations we stand a high probability of loosing them. Do we want to make it easy for the government to take them away?
I believe the noise level over the San Diego meeting is because many users feel economically threatened. Collectively, these users have spent millions of dollars equipping themselves to use L-Band...to use S-Band...because that is what they were encouraged to do. These are the same users who contributed to the construction of our satellites. It is not a resistance to growth or new technology as some have tried to build a case for. Rather a resistance to overnight obsolescence after being urged to adapt these bands, the perceived lack of strong engineering reasons to make such drastic changes, and a lack of input into the decision making process.
Be well -- Bruce
Part of the concern about using L as the primary digital uplink is the fact that the ground stations will be high duty cycle emitters. BPSK has a very low crest factor and one of the uses for a 256 kbps link is streaming video, so it will be very much like an ATV repeater. Given the equatorial orbit, Eagle will also be closer to the horizon than previous amateur HEOs.
Even a restriction similar to the one in place for U uplinks in areas of the U.S. (1 kW EIRP) would make high-speed uplinks unavailable.
73,
John KD6OZH
----- Original Message ----- From: "Bruce Rahn" brahn@woh.rr.com To: K3IO@verizon.net Cc: "AMSAT BB" amsat-bb@amsat.org Sent: Friday, September 22, 2006 05:42 UTC Subject: [amsat-bb] Re: Galileo interference on L band
Tom Clark, K3IO wrote:
Let me add a few comments about why I'm so concerned. The reason that the Galileo E6 (functionally the same as GPS L2, and overlaying the amateur 1260-70 MHz uplink allocation) is important for some uses is that it, when used in combination with the primary 1.57± GHz "L1" frequency (which is what all your cheap hand-held GPS receivers use), can be used to correct the ionospheric errors; the ionosphere adds upwards of 10 meters to the pseudo-range for each GPS satellite. Because of geometric factors (expressed quantitatively in VDOP), this can in turn yield errors in height of up to about 30 meters. [The WAAS and EGNOS signals provide some correction for these biases to the few meter level, but cannot be relied on during severe ionospheric storms.]
Dr. Clark,
There are several issues at play here.
First off, the Galileo E6 is currently specified to serve "Commercial Services" and "Public Regulated Service". Several messages in this thread have discussed "Safety of Life" concerns. E6, as currently publicly stated, will not be used for aircraft navigation. Thus, "Safety of Life" does not come into play when discussing the impacts amateur transmissions may have on E6 users. Amateur transmissions MAY impact commercial and public regulated services, however, the Galileo consortium emphasizes that provisions are being made to mitigate intentional and unintentional interference to these users.
For Galileo users, ionospheric error corrections can be made using E5 and E2/E1 (basically L1) signals. If memory serves me, the greater frequency spread between E5 and E2/E1 should provide slightly more accurate ionospheric error corrections than would be achieved using either E2/E1 and E6 or E5 and E6.
There is a lot of factual evidence that when dual-frequency geodetic GPS receivers (costing ~$25,000 -- hardly cheap!) have been used in proximity to terrestrial amateur L-band stations, the GPS performance is seriously degraded. I direct your attention to several reports on the topic:
* Must reading -- GPS/GLONASS vs L-band digipeaters (Also see GPS World, Oct.2002) (warning contains numbers and equations, as well as uncomplimentary comments about digipeaters)http://elib.uni-stuttgart.de/opus/volltexte/1999/278/pdf/278.pdf#search=%22g... * Amateur and Radar QRM reported at a 1999 technical meeting:
http://www.navcen.uscg.gov/cgsic/meetings/summaryrpts/33rdmeeting/Presentati... * A tutorial that shows how interfering signals can affect a spread spectrum GPS rcvr (caution -- contains more numbers): http://www.rin.org.uk/SITE/UPLOAD/DOCUMENT/Vuln-Owen.pdf#search=%22gps%20ama...
I know very well, first hand, the susceptibility of GPS to unintentional and intentional interference. No arguments there. There is a lot of on-going work in both the military and commercial sectors to mitigate this vulnerability. An example of this is the much more robust waveform L5 will employ as well as higher downlink power levels (as both future GPS and Galileo satellites will employ). There are other technologies at play too. However, the unintentional sources of interference are not just limited to 'problems' caused by the amateur radio community. There was a documented real-world case of a faulty Radio Shack TV antenna amplifier on some pleasure craft in the L.A. area (if memory serves me again) taking out L1 over a wide area in the mid 90's. We won't even talk about the intentional, real-world, threats that are out there. GPS interference mitigation is big business and technology for both the military and commercial sectors will be greatly improved as time marches on.
The amateur radio cases cited in the above references appear to all be high duty cycle emitters with radiation patterns generally aimed at the horizon. I doubt our earth to space uplinks would have the same duty cycles and most of the intentional radiation will be directed above the horizon. This reduces the probability of unintentional interference to GPS, Galileo, and other future systems.
Even though US amateurs may feel that Galileo is a "European only" problem, read carefully Rick's (W2GPS) comments -- in his real life for many years he was a VP with ARINC (the people who worry about standards in the airline industry) and was on many FAA and ICAO committees that decide on airline safety.
Not all US amateurs feel this way. All one has to do is look at the years of effort spent in negotiations between the US and Europeans over Galileo-GPS compatibility issues and spectrum reutilization. That's why E5 and E1/E2 can overlap the GPS L2 and L1 allocations.
Again, from an airline perspective, I will argue there are far more critical threats to GPS/Galileo signal integrity than amateur radio which have to and are being addressed. These threats cannot be regulated or controlled as we amateurs are.
Also realize that the Europeans are absolutely determined to develop their own GNSS (Global Navigation Satellite System) call Galileo -- in part because they don't really trust a system that depends on the US Military, and in part because they see a giga-Euro business opportunity for the EC. Who knows how long it will survive, but the Russians have their competing GLONASS system. And both the Chinese and Japanese see that they need to enter into the GNSS race is they are to be world-class technical competitors.
And it will be interesting to see how this all plays out.
We, the Eagle technical team, have never said that L-band won't work NOW or 5 years from now. But our vision for Eagle is that when the first one flies 4-5 years from now, we want it to be a useful resource for at least a 10 year lifetime. We are very concerned about making a several million dollar (after you count the volunteer builder's blood, sweat & tears) investment only to have it blown away right after launch by the GNSS cartels just because we picked L-band to be anything like a "primary" uplink.
The same concerns could be expressed about ANY of the uplink or downlinks that are planned. ANY of them could be taken away at any time. Spectrum auctions are a wonderful cash cow to Uncle Sam and who knows what special interest groups our elected officials will cater to in the future. However, one thing is historically proven...that if we do not use our amateur allocations we stand a high probability of loosing them. Do we want to make it easy for the government to take them away?
I believe the noise level over the San Diego meeting is because many users feel economically threatened. Collectively, these users have spent millions of dollars equipping themselves to use L-Band...to use S-Band...because that is what they were encouraged to do. These are the same users who contributed to the construction of our satellites. It is not a resistance to growth or new technology as some have tried to build a case for. Rather a resistance to overnight obsolescence after being urged to adapt these bands, the perceived lack of strong engineering reasons to make such drastic changes, and a lack of input into the decision making process.
Be well -- Bruce
John B. Stephensen wrote:
Part of the concern about using L as the primary digital uplink is the fact that the ground stations will be high duty cycle emitters. BPSK has a very low crest factor and one of the uses for a 256 kbps link is streaming video, so it will be very much like an ATV repeater. Given the equatorial orbit, Eagle will also be closer to the horizon than previous amateur HEOs.
Even a restriction similar to the one in place for U uplinks in areas of the U.S. (1 kW EIRP) would make high-speed uplinks unavailable.
John,
Thank you for bringing this point to my attention...through my neglect of things I have lost track of the dominance the digital mode has taken in this project. You are correct that this signal format is a high duty cycle one. My thoughts of where Eagle was heading have been more aligned with the desires of the membership expressed in the survey results presented in the September/October 2004 issue of "The AMSAT Journal".
I'm going to ask some hypothetical questions here which I really don't expect you or anyone to answer. They are more food for thought than anything else.
- As part of the system engineering process, were other bit rates and modulation schemes considered which would mitigate potential interference problems?
- What percentage of the user base (AMSAT-NA members) would be disenfranchised if digital video were eliminated because of its high duty cycle requirements and the potential for causing interference to other spectrum users?
- In the aforementioned survey results, the surveyed members indicated their highest preference was for analog modes followed in second place by digital. Has the user mindset shifted to digital over analog? If not, or unknown, are the spacecraft resources being fairly partitioned and allocated to support analog users? What percentage of the user community will be using digital video and text messaging?
In a private exchange with Mr. Sanford, I expressed my concern that the user community was not being represented by a strong 'user advocate' at critical design meetings. 'Designers are not users and users are not designers' but both camps must be fairly represented to achieve harmony and consensus between the two. Bringing a strong 'user advocate' into the design process would be a win-win situation for both the user community as well as the design community. Users would feel someone is directly addressing their operational concerns and the 'user advocate' could be the one defending decisions rather than occupying the time of the designers in addressing these concerns.
I believe in the 20 plus years I have been an AMSAT member history has demonstrated that the 'if we build it they will come' approach has not worked well. Had it been successful, the organization would have more resources in terms of members and dollars than we could deal with.
Respectfully -- Bruce
The digital mode is not dominant as Eagle is to provide simultaneous analog and digital service. I don't see that using U as the primary uplink and and making L the secondary uplink for the linear transponder is a big problem. P3E designers made the same choice by having the L antenna work only near apogee.
The digital service will be used by those AMSAT members interested in it and we think that it will attract more members to pay for these satellites. The intent is to support 3 digital transponder bit rates - approximately 50 bps, 4800 bps and 256 kbps -- as described in the San Diego meeting document on EaglePedia. 4800 bps allows for digital voice uplinks and downlinks over 75% of the orbit with smaller antennas and less power than we need now for SSB. No one could come up with a modulation scheme (even SSB) that would eliminate the potental for interference on L band as the power spectral density of the uplink signal is so much higher than the Galileo downlink signal. This is why another band was recommended as the primary digital uplink.
As far as I can tell, AMSAT has put the linear transponders that the majority of its members wanted on each phase 3 satellite. Adding digital services that the rest of the world is using seems likely to attract more members than continuing with the same old strategy.
73,
John KD6OZH
----- Original Message ----- From: "Bruce Rahn" brahn@woh.rr.com To: "John B. Stephensen" kd6ozh@comcast.net Cc: K3IO@verizon.net; "AMSAT BB" amsat-bb@amsat.org Sent: Friday, September 22, 2006 21:27 UTC Subject: Re: [amsat-bb] Re: Galileo interference on L band
John B. Stephensen wrote:
Part of the concern about using L as the primary digital uplink is the fact that the ground stations will be high duty cycle emitters. BPSK has a very low crest factor and one of the uses for a 256 kbps link is streaming video, so it will be very much like an ATV repeater. Given the equatorial orbit, Eagle will also be closer to the horizon than previous amateur HEOs.
Even a restriction similar to the one in place for U uplinks in areas of the U.S. (1 kW EIRP) would make high-speed uplinks unavailable.
John,
Thank you for bringing this point to my attention...through my neglect of things I have lost track of the dominance the digital mode has taken in this project. You are correct that this signal format is a high duty cycle one. My thoughts of where Eagle was heading have been more aligned with the desires of the membership expressed in the survey results presented in the September/October 2004 issue of "The AMSAT Journal".
I'm going to ask some hypothetical questions here which I really don't expect you or anyone to answer. They are more food for thought than anything else.
- As part of the system engineering process, were other bit rates and
modulation schemes considered which would mitigate potential interference problems?
- What percentage of the user base (AMSAT-NA members) would be
disenfranchised if digital video were eliminated because of its high duty cycle requirements and the potential for causing interference to other spectrum users?
- In the aforementioned survey results, the surveyed members indicated
their highest preference was for analog modes followed in second place by digital. Has the user mindset shifted to digital over analog? If not, or unknown, are the spacecraft resources being fairly partitioned and allocated to support analog users? What percentage of the user community will be using digital video and text messaging?
In a private exchange with Mr. Sanford, I expressed my concern that the user community was not being represented by a strong 'user advocate' at critical design meetings. 'Designers are not users and users are not designers' but both camps must be fairly represented to achieve harmony and consensus between the two. Bringing a strong 'user advocate' into the design process would be a win-win situation for both the user community as well as the design community. Users would feel someone is directly addressing their operational concerns and the 'user advocate' could be the one defending decisions rather than occupying the time of the designers in addressing these concerns. I believe in the 20 plus years I have been an AMSAT member history has demonstrated that the 'if we build it they will come' approach has not worked well. Had it been successful, the organization would have more resources in terms of members and dollars than we could deal with.
Respectfully -- Bruce
-- Bruce Rahn
Wisdom has two parts:
- having a lot to say; and
- not saying it!
will this be like Slow Scan TV? Otherwise for passing video we have the internet which is much more reliable and easier to use. A HEO sat advantage is to work DX, unlike a LEO sat. Will we be able to operate RTTY and Psk31 via Eagle? If so then it might be a nice way to work on DXCC Digital (RTTY & Psk31) awards. But can we use satellite contacts as credit for DXCC awards? Is there a DXCC video award that exists now or in the future?
I am sure Eagle will be fun for many users to use in maybe 5-10 years. I certainly see no chance of us building and launching it in less than 5 years. After that I think a more practical goal would be to launch one HEO every 10 years. Don't know about the rest of you but our property taxes are going up a lot here. One ham friend's house jumped from $5,500 last year to $6,000 this year.
Les W4SCO
At 06:40 PM 9/22/2006, John B. Stephensen wrote:
The digital mode is not dominant as Eagle is to provide simultaneous analog and digital service. I don't see that using U as the primary uplink and and making L the secondary uplink for the linear transponder is a big problem. P3E designers made the same choice by having the L antenna work only near apogee.
The digital service will be used by those AMSAT members interested in it and we think that it will attract more members to pay for these satellites. The intent is to support 3 digital transponder bit rates - approximately 50 bps, 4800 bps and 256 kbps -- as described in the San Diego meeting document on EaglePedia. 4800 bps allows for digital voice uplinks and downlinks over 75% of the orbit with smaller antennas and less power than we need now for SSB. No one could come up with a modulation scheme (even SSB) that would eliminate the potental for interference on L band as the power spectral density of the uplink signal is so much higher than the Galileo downlink signal. This is why another band was recommended as the primary digital uplink.
As far as I can tell, AMSAT has put the linear transponders that the majority of its members wanted on each phase 3 satellite. Adding digital services that the rest of the world is using seems likely to attract more members than continuing with the same old strategy.
73,
John KD6OZH
----- Original Message ----- From: "Bruce Rahn" brahn@woh.rr.com To: "John B. Stephensen" kd6ozh@comcast.net Cc: K3IO@verizon.net; "AMSAT BB" amsat-bb@amsat.org Sent: Friday, September 22, 2006 21:27 UTC Subject: Re: [amsat-bb] Re: Galileo interference on L band
John B. Stephensen wrote:
Part of the concern about using L as the primary digital uplink is the fact that the ground stations will be high duty cycle emitters. BPSK has a very low crest factor and one of the uses for a 256 kbps link is streaming video, so it will be very much like an ATV repeater. Given the equatorial orbit, Eagle will also be closer to the horizon than previous amateur HEOs.
Even a restriction similar to the one in place for U uplinks in areas of the U.S. (1 kW EIRP) would make high-speed uplinks unavailable.
John,
Thank you for bringing this point to my attention...through my neglect of things I have lost track of the dominance the digital mode has taken in this project. You are correct that this signal format is a high duty cycle one. My thoughts of where Eagle was heading have been more aligned with the desires of the membership expressed in the survey results presented in the September/October 2004 issue of "The AMSAT Journal".
I'm going to ask some hypothetical questions here which I really don't expect you or anyone to answer. They are more food for thought than anything else.
- As part of the system engineering process, were other bit rates and
modulation schemes considered which would mitigate potential interference problems?
- What percentage of the user base (AMSAT-NA members) would be
disenfranchised if digital video were eliminated because of its high duty cycle requirements and the potential for causing interference to other spectrum users?
- In the aforementioned survey results, the surveyed members indicated
their highest preference was for analog modes followed in second place by digital. Has the user mindset shifted to digital over analog? If not, or unknown, are the spacecraft resources being fairly partitioned and allocated to support analog users? What percentage of the user community will be using digital video and text messaging?
In a private exchange with Mr. Sanford, I expressed my concern that the user community was not being represented by a strong 'user advocate' at critical design meetings. 'Designers are not users and users are not designers' but both camps must be fairly represented to achieve harmony and consensus between the two. Bringing a strong 'user advocate' into the design process would be a win-win situation for both the user community as well as the design community. Users would feel someone is directly addressing their operational concerns and the 'user advocate' could be the one defending decisions rather than occupying the time of the designers in addressing these concerns. I believe in the 20 plus years I have been an AMSAT member history has demonstrated that the 'if we build it they will come' approach has not worked well. Had it been successful, the organization would have more resources in terms of members and dollars than we could deal with.
Respectfully -- Bruce
-- Bruce Rahn
Wisdom has two parts:
- having a lot to say; and
- not saying it!
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
256 kbps MPEG4 video is not quite TV broadcast quality but quite good. I'll send you a file separately. There are many hams that operate ATV and this is the only way to provide that mode nationally and internationally. The other impetus for 256 kbps is that NGOs need it for emergency data communications. Another use could be to provide an SSTV-like service, but with high-resolution images.
RTTY is discouraged on linear transponders because of the low crest factor and PSK31 has problems with doppler. The purpose of the class 1 digital service is to provide a PSK31-like service with small omnidirectional antennas, like M2 eggbeaters.
I don't remember the DXCC rules for satellites, but I'm sure that they are on the ARRL web site.
73,
John KD6OZH
----- Original Message ----- From: sco@sco-inc.com To: "amsat bb" amsat-bb@amsat.org Sent: Friday, September 22, 2006 23:19 UTC Subject: [amsat-bb] Re: Galileo interference on L band
will this be like Slow Scan TV? Otherwise for passing video we have the internet which is much more reliable and easier to use. A HEO sat advantage is to work DX, unlike a LEO sat. Will we be able to operate RTTY and Psk31 via Eagle? If so then it might be a nice way to work on DXCC Digital (RTTY & Psk31) awards. But can we use satellite contacts as credit for DXCC awards? Is there a DXCC video award that exists now or in the future?
I am sure Eagle will be fun for many users to use in maybe 5-10 years. I certainly see no chance of us building and launching it in less than 5 years. After that I think a more practical goal would be to launch one HEO every 10 years. Don't know about the rest of you but our property taxes are going up a lot here. One ham friend's house jumped from $5,500 last year to $6,000 this year.
Les W4SCO
At 06:40 PM 9/22/2006, John B. Stephensen wrote:
The digital mode is not dominant as Eagle is to provide simultaneous analog and digital service. I don't see that using U as the primary uplink and and making L the secondary uplink for the linear transponder is a big problem. P3E designers made the same choice by having the L antenna work only near apogee.
The digital service will be used by those AMSAT members interested in it and we think that it will attract more members to pay for these satellites. The intent is to support 3 digital transponder bit rates - approximately 50 bps, 4800 bps and 256 kbps -- as described in the San Diego meeting document on EaglePedia. 4800 bps allows for digital voice uplinks and downlinks over 75% of the orbit with smaller antennas and less power than we need now for SSB. No one could come up with a modulation scheme (even SSB) that would eliminate the potental for interference on L band as the power spectral density of the uplink signal is so much higher than the Galileo downlink signal. This is why another band was recommended as the primary digital uplink.
As far as I can tell, AMSAT has put the linear transponders that the majority of its members wanted on each phase 3 satellite. Adding digital services that the rest of the world is using seems likely to attract more members than continuing with the same old strategy.
73,
John KD6OZH
----- Original Message ----- From: "Bruce Rahn" brahn@woh.rr.com To: "John B. Stephensen" kd6ozh@comcast.net Cc: K3IO@verizon.net; "AMSAT BB" amsat-bb@amsat.org Sent: Friday, September 22, 2006 21:27 UTC Subject: Re: [amsat-bb] Re: Galileo interference on L band
John B. Stephensen wrote:
Part of the concern about using L as the primary digital uplink is the fact that the ground stations will be high duty cycle emitters. BPSK has a very low crest factor and one of the uses for a 256 kbps link is streaming video, so it will be very much like an ATV repeater. Given the equatorial orbit, Eagle will also be closer to the horizon than previous amateur HEOs.
Even a restriction similar to the one in place for U uplinks in areas of the U.S. (1 kW EIRP) would make high-speed uplinks unavailable.
John,
Thank you for bringing this point to my attention...through my neglect of things I have lost track of the dominance the digital mode has taken in this project. You are correct that this signal format is a high duty cycle one. My thoughts of where Eagle was heading have been more aligned with the desires of the membership expressed in the survey results presented in the September/October 2004 issue of "The AMSAT Journal".
I'm going to ask some hypothetical questions here which I really don't expect you or anyone to answer. They are more food for thought than anything else.
- As part of the system engineering process, were other bit rates and
modulation schemes considered which would mitigate potential interference problems?
- What percentage of the user base (AMSAT-NA members) would be
disenfranchised if digital video were eliminated because of its high duty cycle requirements and the potential for causing interference to other spectrum users?
- In the aforementioned survey results, the surveyed members indicated
their highest preference was for analog modes followed in second place by digital. Has the user mindset shifted to digital over analog? If not, or unknown, are the spacecraft resources being fairly partitioned and allocated to support analog users? What percentage of the user community will be using digital video and text messaging?
In a private exchange with Mr. Sanford, I expressed my concern that the user community was not being represented by a strong 'user advocate' at critical design meetings. 'Designers are not users and users are not designers' but both camps must be fairly represented to achieve harmony and consensus between the two. Bringing a strong 'user advocate' into the design process would be a win-win situation for both the user community as well as the design community. Users would feel someone is directly addressing their operational concerns and the 'user advocate' could be the one defending decisions rather than occupying the time of the designers in addressing these concerns. I believe in the 20 plus years I have been an AMSAT member history has demonstrated that the 'if we build it they will come' approach has not worked well. Had it been successful, the organization would have more resources in terms of members and dollars than we could deal with.
Respectfully -- Bruce
-- Bruce Rahn
Wisdom has two parts:
- having a lot to say; and
- not saying it!
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "John B. Stephensen" kd6ozh@comcast.net To: "amsat bb" amsat-bb@amsat.org; sco@sco-inc.com Sent: Friday, September 22, 2006 7:16 PM Subject: [amsat-bb] Re: Galileo interference on L band
<snip>
The other impetus for 256 kbps is that NGOs need it for emergency data communications. Another use could be to provide an SSTV-like service, but with high-resolution images.
<snip>
Someone please correct me if I'm wrong, but wasn't AO-51 made available for disaster communications after the Christmas tsunami, yet NOT ONE piece of disaster traffic was ever passed on it? Was ANY disaster traffic ever passed on any of our satellites after Katrina? Yet, how many hundreds or thousands of messages were passed on HF and 2 meters?
Why? Because HF and 2 meter nets work 24/7, and no emergency agency, whether governmental or NGO, wants to wait for a satellite to come over the horizon to pass their traffic.
Until such time as we have either a fleet of HEOs (or a geostationary satellite) providing 24/7 access (at least 15 years off), I have to seriously question how useful any NGO would find a 256kbps data link that's only available a few times a day, and for relatively short periods of time......... especially when the Red Cross disaster response vehicle that was at our hamfest has a ZERO-SETUP, instant-on, 24/7 high-speed satellite internet connection (HughesNet, I think), with both CAT5e and WiFi connection sharing. I believe SATERN either has, or is looking at, the same type of setup.
Has the design team received any input from the NGOs on this emergency data "need"? If so, please share it.
(and while I have the floor, it's "lose" and "losing", not "loose" or "loosing".... and don't even get me started on "there", "their", and "they're"! We're supposed to be COMMUNICATORS, for God's sake!)
Why would it be available for only short periods? Eagle is a HEO.
73,
John KD6OZH
----- Original Message ----- From: "George Henry" ka3hsw@earthlink.net To: "amsat bb" amsat-bb@amsat.org Sent: Saturday, September 23, 2006 19:51 UTC Subject: [amsat-bb] Eagle and emergency traffic (was Re: Galileointerference on L band)
----- Original Message ----- From: "John B. Stephensen" kd6ozh@comcast.net To: "amsat bb" amsat-bb@amsat.org; sco@sco-inc.com Sent: Friday, September 22, 2006 7:16 PM Subject: [amsat-bb] Re: Galileo interference on L band
<snip>
The other impetus for 256 kbps is that NGOs need it for emergency data communications. Another use could be to provide an SSTV-like service, but with high-resolution images.
<snip>
Someone please correct me if I'm wrong, but wasn't AO-51 made available for disaster communications after the Christmas tsunami, yet NOT ONE piece of disaster traffic was ever passed on it? Was ANY disaster traffic ever passed on any of our satellites after Katrina? Yet, how many hundreds or thousands of messages were passed on HF and 2 meters?
Why? Because HF and 2 meter nets work 24/7, and no emergency agency, whether governmental or NGO, wants to wait for a satellite to come over the horizon to pass their traffic.
Until such time as we have either a fleet of HEOs (or a geostationary satellite) providing 24/7 access (at least 15 years off), I have to seriously question how useful any NGO would find a 256kbps data link that's only available a few times a day, and for relatively short periods of time......... especially when the Red Cross disaster response vehicle that was at our hamfest has a ZERO-SETUP, instant-on, 24/7 high-speed satellite internet connection (HughesNet, I think), with both CAT5e and WiFi connection sharing. I believe SATERN either has, or is looking at, the same type of setup.
Has the design team received any input from the NGOs on this emergency data "need"? If so, please share it.
(and while I have the floor, it's "lose" and "losing", not "loose" or "loosing".... and don't even get me started on "there", "their", and "they're"! We're supposed to be COMMUNICATORS, for God's sake!)
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
----- Original Message ----- From: "John B. Stephensen" kd6ozh@comcast.net To: "George Henry" ka3hsw@earthlink.net; "amsat bb" amsat-bb@amsat.org Sent: Saturday, September 23, 2006 5:08 PM Subject: Re: [amsat-bb] Eagle and emergency traffic (was Re: Galileointerference on L band)
Why would it be available for only short periods? Eagle is a HEO.
73,
John KD6OZH
I said RELATIVELY short periods... what is the maximum time that the proposed data transponder will be available to a given ground station, with favorable squint angles, on any given orbit? What is the TOTAL, cumulative access time per day? From the perspective of an emergency manager or disaster team captain, it is certain to seem small when 24/7 service is available from other sources, particularly sources that they have already invested in. And since the design team is looking into their crystal ball at what the state of things will be 5 years down the road at launch, surely they have seen that the entire internet access landscape is sure to have undergone a sea change by then? (Bill Gates sure seems certain of that...)
I repeat: if the design team has anything from the NGOs to bolster the claim that they (NGOs) "need it for emergency data communications", then let's see it.
George Henry wrote:
----- Original Message ----- From: "John B. Stephensen" kd6ozh@comcast.net To: "George Henry" ka3hsw@earthlink.net; "amsat bb" amsat-bb@amsat.org Sent: Saturday, September 23, 2006 5:08 PM Subject: Re: [amsat-bb] Eagle and emergency traffic (was Re: Galileointerference on L band)
Why would it be available for only short periods? Eagle is a HEO.
73,
John KD6OZH
I said RELATIVELY short periods... what is the maximum time that the proposed data transponder will be available to a given ground station, with favorable squint angles, on any given orbit? What is the TOTAL, cumulative access time per day? From the perspective of an emergency manager or disaster team captain, it is certain to seem small when 24/7 service is available from other sources, particularly sources that they have already invested in. And since the design team is looking into their crystal ball at what the state of things will be 5 years down the road at launch, surely they have seen that the entire internet access landscape is sure to have undergone a sea change by then? (Bill Gates sure seems certain of that...)
I repeat: if the design team has anything from the NGOs to bolster the claim that they (NGOs) "need it for emergency data communications", then let's see it.
I don't believe anyone said we had a directive to provide a service. How could we have such a directive when we don't have the satellite designed yet? What NGO or government agency do you know would empower us to do something or even ask based on a hope we get our facility launched in the next half decade? I wouldn't go see them about using us in their planning until such time as the facility was actually available. That does not make it a sin or a fault to hope to provide that facility and to think about what it would take to make it possible. I certainly don't hang my head in shame because I have those thoughts. In fact, I am kind of proud of us for taking it into consideration.
Eagle is being designed to provide long term access per bird as compared to previous and planned P3 birds. The advanced communications package is being designed around the use of phased arrays. The phased array design is targeting 70% of the orbit to be usable per bird. If we choose to stay in a 12 hour orbit, that is 8-ish hours per orbit. The only way this can be made to work in a usable fashion, providing voice, conferencing, data/file transfer is the use of digital signaling. Admittedly, no ground station will see every orbit since we are also aiming for an equatorial orbit. We need more than one bird.
73's Bob N4HY
Points addressed below:
----- Original Message ----- From: "Robert McGwier" rwmcgwier@comcast.net To: "George Henry" ka3hsw@earthlink.net Cc: "amsat bb" amsat-bb@amsat.org Sent: Sunday, September 24, 2006 1:56 AM Subject: Re: [amsat-bb] Re: Eagle and emergency traffic (was Re: Galileointerference on L band)
<snip>
I said RELATIVELY short periods... what is the maximum time that the proposed data transponder will be available to a given ground station, with favorable squint angles, on any given orbit? What is the TOTAL, cumulative access time per day? From the perspective of an emergency manager or disaster team captain, it is certain to seem small when 24/7 service is available from other sources, particularly sources that they have already invested in. And since the design team is looking into their crystal ball at what the state of things will be 5 years down the road at launch, surely they have seen that the entire internet access landscape is sure to have undergone a sea change by then? (Bill Gates sure seems certain of that...)
I repeat: if the design team has anything from the NGOs to bolster the claim that they (NGOs) "need it for emergency data communications", then let's see it.
I don't believe anyone said we had a directive to provide a service. How could we have such a directive when we don't have the satellite designed yet? What NGO or government agency do you know would empower us to do something or even ask based on a hope we get our facility launched in the next half decade? I wouldn't go see them about using us in their planning until such time as the facility was actually available. That does not make it a sin or a fault to hope to provide that facility and to think about what it would take to make it possible. I certainly don't hang my head in shame because I have those thoughts. In fact, I am kind of proud of us for taking it into consideration.
John's original message said, and I quote, "...The other impetus for 256 kbps is that NGOs need it for emergency data communications." When I see a statement like that, I expect to see hard and fast facts to back it up. John has since clarified that it is not an explicitly stated NEED, but rather a WANT that the NGOs have expressed "for years." (What parent hasn't tried to make their child(ren) understand the difference between "need" and "want?")
Semantics aside, I pointed out that at least one of those NGOs (the American Red Cross) has poured tens, if not hundreds, of thousands of dollars into a commercial satellite internet solution, likely rendering our efforts to eventually meet that same want, obsolete. By the time Eagle is bolted to the launch ring, satellite-connected laptops are likely to be an affordable reality for any disaster relief agency.
By all means, DO consider the possibilities, but don't lose sight of the realities in the process.
Eagle is being designed to provide long term access per bird as compared to previous and planned P3 birds. The advanced communications package is being designed around the use of phased arrays. The phased array design is targeting 70% of the orbit to be usable per bird. If we choose to stay in a 12 hour orbit, that is 8-ish hours per orbit. The only way this can be made to work in a usable fashion, providing voice, conferencing, data/file transfer is the use of digital signaling. Admittedly, no ground station will see every orbit since we are also aiming for an equatorial orbit. We need more than one bird.
Precisely the first point I tried to make: anything less than 24/7 access is not likely to be viewed as very useful. In a disaster, I'd love to be able to be on a satellite as I pull out of my driveway, like I can be on 40 meters thru 70cm today. The reality is that any bird that I *could* be on today, would be gone in 15 minutes or less. Sadly, our current crop of satellites is ill-suited to emergency communications, and it will be at least 15 years before we can offer 24/7 coverage. It doesn't mean that we shouldn't try: it just means that we should recognize the possibility that disaster communications may never be our "niche". In 15 years, other data communications technologies will, almost certainly, affordably eclipse what we have put into orbit. And I don't know that AMSAT donors can ever afford the $$ to get ahead of that technology curve, which has VERY deep pockets driving it.
73, George, KA3HSW
At 05:25 PM 24-09-2006, George Henry wrote:
Semantics aside, I pointed out that at least one of those NGOs (the American Red Cross) has poured tens, if not hundreds, of thousands of dollars into a commercial satellite internet solution, likely rendering our efforts to eventually meet that same want, obsolete.
I've operated the Red Cross system VSAT system. It's good, 2 or 4 Mbps service with a DHCP server or fixed IP address available as part of the radio package. They use the service [1] to extend the data network supporting the in-house IP telephone system and computer system and [2] to operate land mobile base stations remotely. Works very well, once it's going. (Let save third party traffic and cyphers for another time.)
At the same time, the Red Cross system is anything but nimble. Deployment from a limited stock of equipment can take days for shipment (problematic into disaster areas) and hours to get into service. With some pre-assembly, once on site, a good crew of two well trained technicians can get one of the Red Cross VSAT stations on the air in an hour or two. Finding the well trained technicians is another problem.
In essence, the Red Cross' major issues are quantity, transportation, and training.
Hams usually have big advantages in all three areas.
If all we can deliver is short lead time 250 kbps service for 18 hours a day, they'll be very happy, indeed.
73, art..... W4ART Arlington, VA
Life is short. Be swift to love! Make haste to be kind! - Henri Frederic Amiel, philosopher and writer (1821-1881)
Quoting Arthur Feller afeller@ieee.org:
At the same time, the Red Cross system is anything but nimble. Deployment from a limited stock of equipment can take days for shipment (problematic into disaster areas) and hours to get into service. With some pre-assembly, once on site, a good crew of two well trained technicians can get one of the Red Cross VSAT stations on the air in an hour or two. Finding the well trained technicians is another problem.
In essence, the Red Cross' major issues are quantity, transportation, and training.
Hams usually have big advantages in all three areas.
If all we can deliver is short lead time 250 kbps service for 18 hours a day, they'll be very happy, indeed.
73, art..... W4ART Arlington, VA
It seems to me that the best that hams can offer, and have ever offered, in any emergency communications is redundancy. Put it another way, I'd be horrified if our nations' emergency services did not have the resources to avail themselves of the modes and means that we amateurs cobble together.
However, this is a redundancy in overwhelming depth, and that has its uses. I imagine the Red Cross (US) cannot send out 1,000 satellite stations; but when Eagle is flying I'd expect that's around the number of digital stations we might have working in the US. If one of those were to be deployed in an emergency, its role would be to assist in bringing on-line the Red Cross' system, and thereafter to provide backup, but I would think this would be a quite valued role.
Indeed, the argument seen on this list recently, which claims that any efforts of ours to provide emergency services would be pointless because of the deeper pockets of the professionals, cuts against *any* amateur role in emergency response in any mode and on any band. Given that amateurs seem to be in fact making a difference in these ventures and being appreicated for it, I would say there must be some fault with that argument.
I think there's much to allow one's imagination play over regarding Eagle's user classes. Consider the role of the U/V text messaging in all this. A 2m rig hooked up to the jumpkit laptop could provide an easily set-up, out-of-band conversation to help bootstrap the internet connection with info such as accurate time (needed for pointing), IP addresses, etc.
73, Bruce VE9QRP
You need to go back and re-read my previous posts, because you have missed, and mis-interpreted, several of my points...
----- Original Message ----- From: "Bruce Robertson" broberts@mta.ca To: amsat-bb@amsat.org Sent: Sunday, September 24, 2006 7:47 PM Subject: [amsat-bb] Re: Eagle and emergency traffic
<snip>
It seems to me that the best that hams can offer, and have ever offered, in any emergency communications is redundancy. Put it another way, I'd be horrified if our nations' emergency services did not have the resources to avail themselves of the modes and means that we amateurs cobble together.
Absolutely no argument there...
However, this is a redundancy in overwhelming depth, and that has its uses. I imagine the Red Cross (US) cannot send out 1,000 satellite stations; but when Eagle is flying I'd expect that's around the number of digital stations we might have working in the US. If one of those were to be deployed in an emergency, its role would be to assist in bringing on-line the Red Cross' system, and thereafter to provide backup, but I would think this would be a quite valued role.
I think that 1000 US stations is a very optimistic number for this mode, especially considering that these high-speed digital stations don't exist AT ALL today, and will have to be built from scratch at not-insubstantial cost, but see more below...
Indeed, the argument seen on this list recently, which claims that any efforts of ours to provide emergency services would be pointless because of
I never said that our efforts would be "pointless," only that *this particular application* would likely be obsolete before launch, and not because of the deep pockets of the professionals, but because of the deep pockets driving data communications (specifically, internet) technology to be smaller, faster, more reliable, more ubiquitous, and less expensive. I challenged the statement that "...NGOs need [256 kbps on Eagle] for emergency data communications." I eventually was told by the author of that statement that it was not, in fact, a stated need, but rather, a long-standing desire of the NGOs. I then pointed out that one of those very NGOs had already invested heavily in an alternative mode of data communications in the meantime.
the deeper pockets of the professionals, cuts against *any* amateur role in emergency response in any mode and on any band. Given that amateurs seem to
Quite the contrary! There are, unquestionably, things that we amateurs do very well in emergency communications, and they are well-recognized by the disaster services community. I am proud to say (contrary to Dave Guimont's suggestion) that I spent 5 years working with Red Cross Disaster Services in Scranton, PA, where I was called out for several mine collapses and a couple of spectacular fires. I have been an active National Weather Service tornado spotter here in Illinois for over 15 years, with hundreds of hours in the field and in the OEM. I am a former EMT/firefighter, and I have drilled extensively in all of those capacities. Granted, I have not yet been involved in a full-fledged disaster situation (I missed the Plainfield tornado disaster out here by 1 year), but have seen action on both ends of numerous emergencies. I have seen spectacular successes and dismal failures, both by the professionals and by us amateurs. What I have NOT seen, to date, is an amateur satellite playing any role in an emergency, and I believe (and said) that this is simply because right now, we have other systems that are just better suited. Just consider Field Day: which station usually takes the longest to set up? Satellite. Which station has the lowest Q rate? Satellite. In fact, any one of the HF stations makes more Q's in 10 minutes than most satellite stations do for the whole weekend. The parallels to a real disaster should not be hard to see.
be in fact making a difference in these ventures and being appreicated for it, I would say there must be some fault with that argument.
No question, what we do now, we do well, and we ARE appreciated for it. Witness Homeland Secuity's glowing assessment of the role of amateur radio in the aftermath of Katrina.
I think there's much to allow one's imagination play over regarding Eagle's user classes. Consider the role of the U/V text messaging in all this. A 2m rig hooked up to the jumpkit laptop could provide an easily set-up, out-of-band conversation to help bootstrap the internet connection with info such as accurate time (needed for pointing), IP addresses, etc.
Now HERE, on U/V, you may very well find 1000 US stations active in a disaster, as many are already equipped for this mode.
I have tried to make myself as clear as I can in these posts. If people don't get it by now, I am sorry: I doubt that I can make it any clearer. I am done with this thread.
Quoting George Henry ka3hsw@earthlink.net:
You need to go back and re-read my previous posts, because you have missed, and mis-interpreted, several of my points...
I'm sorry if I did, George. Though I was responding to a thread you began, I didn't mean for my comments to respond directly to yours, rather to the general discussion on this list which has taken place over the past couple of weeks. I appreciate your experienced perspective on the questions.
I take your point that emergency services might not like the experimental and periodic nature of the digital mode on Eagle, but then I suppose we might reply that we'll never get there until we experiment with it, and we can't have continuous service before we have periodic service. My impression is that you wisely wish us not to over-sell our abilities or capacities. That's good advice.
Furthermore, there appears to be good-faith disagreement as to, as you say, "how useful any NGO would find a 256kbps data link that's only available a few times a day." These is an important question: you do a service by raising it, and we (or AMSAT representatives) should dispassionately investigate it.
One further point which might be of interest. If you're intrigued by the emergency comm. potential of the U/V messaging service on Eagle, note that it is meant to require only an omni antenna. Those lower requirements might increase the installed base considerably beyond the 1000 we'd been passing around.
73, Bruce VE9QRP
At 04:25 PM 9/24/2006 -0500, George Henry wrote: ===snip===
Precisely the first point I tried to make: anything less than 24/7 access is not likely to be viewed as very useful. In a disaster, I'd love to be able to be on a satellite as I pull out of my driveway, like I can be on 40 meters thru 70cm today. The reality is that any bird that I *could* be on today, would be gone in 15 minutes or less. Sadly, our current crop of satellites is ill-suited to emergency communications, and it will be at least 15 years before we can offer 24/7 coverage. It doesn't mean that we shouldn't try: it just means that we should recognize the possibility that disaster communications may never be our "niche". In 15 years, other data communications technologies will, almost certainly, affordably eclipse what we have put into orbit. And I don't know that AMSAT donors can ever afford the $$ to get ahead of that technology curve, which has VERY deep pockets driving it.
73, George, KA3HSW
George,
Comparing Eagle, P3E, or other past HEO's to the current Leo's is like comparing a kite to a jet aircraft...both fly but that's all that is common. Maybe you have had no experience with Heo's, but AO-40 was accessible to me for periods of up to 16 continuous hours per day! That may not be 7/24 but it whole lot different than 15-minutes time three passes per day for AO-51!
However, your point that commercial satellite technology may likely provide 7/24 access for EnComm by the time Eagle flies is valid. Still ham radio with its decentralized, diverse distribution of resources still seems to work better than the best made plans of the bureaucracies! It may be fine that the Red Cross or FEMA have inventories for satellite comms....but they still need to get where they are needed...seems that was where the Katrina response failed (100's of trailers stored in Arkansas and survivors still waiting for a trailer...Nat'l Guard not able to comm with other units by radio and resorting to runners with written messages...one sat phone for the Nat'l Guard in the whole Gulf area...forgetting to fuel backup generators for cellualr sites...lots of special EnComm gear that didn't work because the repeaters had no power...the list is endless). So it may not be perfect but ham radio often is all that works...even if not 7/24.
I think we still can play a role. The concept is good, if not perfect. It is good PR for ham radio and Satellite ham radio. "If it is worth doing, its worth doing imperfectly"! 73's, Ed - KL7UW =================================== BP40iq, Nikiski, AK http://www.qsl.net/al7eb Amsat #3212 Modes: V - U - L - S ===================================
The goal is availability over 3/4 of the orbit for both SSB users and users of newer modes. 2 satellites in the right orbits could provide availability close to 3/4 of the time. This is good for all amateurs as they can use satellites when it is convenient for them rather than scheduling their activities around the satellite.
NGOs have stated to various ARRL committee members that they want digital communication at as high a speed as possible 24/7 -- this has been known for years and is why the ARRL is encouraging use of HF digital links (even though they are slow) for emergency traffic. The fact that technology has advanced to the point that amateur satellites can do this is a good as it can give us another application for the satellite and another group of hams that can become interested and more potential donors.
The nice thing about digital commnication and digital signal processing is that we can use it to allow voice communication for hams with small stations and then re-use the same hardware for high-speed data for larger earth stations.
73,
John KD6OZH
----- Original Message ----- From: "George Henry" ka3hsw@earthlink.net To: "amsat bb" amsat-bb@amsat.org Sent: Sunday, September 24, 2006 03:15 UTC Subject: [amsat-bb] Re: Eagle and emergency traffic (was Re:Galileointerference on L band)
----- Original Message ----- From: "John B. Stephensen" kd6ozh@comcast.net To: "George Henry" ka3hsw@earthlink.net; "amsat bb" amsat-bb@amsat.org Sent: Saturday, September 23, 2006 5:08 PM Subject: Re: [amsat-bb] Eagle and emergency traffic (was Re: Galileointerference on L band)
Why would it be available for only short periods? Eagle is a HEO.
73,
John KD6OZH
I said RELATIVELY short periods... what is the maximum time that the proposed data transponder will be available to a given ground station, with favorable squint angles, on any given orbit? What is the TOTAL, cumulative access time per day? From the perspective of an emergency manager or disaster team captain, it is certain to seem small when 24/7 service is available from other sources, particularly sources that they have already invested in. And since the design team is looking into their crystal ball at what the state of things will be 5 years down the road at launch, surely they have seen that the entire internet access landscape is sure to have undergone a sea change by then? (Bill Gates sure seems certain of that...)
I repeat: if the design team has anything from the NGOs to bolster the claim that they (NGOs) "need it for emergency data communications", then let's see it.
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
On 22 Sep 2006 at 22:40, John B. Stephensen wrote:
The digital mode is not dominant as Eagle is to provide simultaneous analog and digital service.>
As far as I can tell, AMSAT has put the linear transponders that the majority of its members wanted on each phase 3 satellite. Adding digital services that the rest of the world is using seems likely to attract more members than continuing with the same old strategy.
73,
John KD6OZH
My dear Mr Stephenson ESQ
There is also a lot of cube sats in the making who will also carry on digital capabilities but for the sake of the AMSAT'S Can we let them carry on a simple satellite where you and me can discuss of you ideas. As you and me are also aware it is not all the satellite community who can use digital modes.
On the rest i agree with you but it seems there is not enough space available in Eagle and i'm afraid many will missed the train. I think P3E will have some sort of digital system.
"-" The medium is the message...The content is the audience...;)
Luc Leblanc VE2DWE WAC basic,CW,Phone,Satellite Skype VE2DWE www.qsl.net/ve2dwe
Remember that the purpose of the digital modes on Eagle is different from PACSATs. The object of the ACP is to make a HEO EasySat that provides worldwide communications with smaller antennas. Class 1 provides a PSK31-like service with small, fixed antennas on the ground. Since it's U/V and most amateurs have PCs, most will probably be able to use it. However the real reason is to make AMSAT satellites available to more people at a lower ground station cost and also make them easier to use from remote locations. Class 2 provides digital voice and data with smaller rotatable antennas than needed today so it allows hams with limited space to use the satellite. It also makes portable stations smaller. Class 3 just allows larger ground stations to do more things -- with bigger antennas and more uplink power they can push more bits through the same hardware as class 2 users.
73,
John KD6OZH
----- Original Message ----- From: "Luc Leblanc VE2DWE" lucleblanc6@videotron.ca To: AMSAT-BB@amsat.org Sent: Saturday, September 23, 2006 05:05 UTC Subject: [amsat-bb] Re: Galileo interference on L band
On 22 Sep 2006 at 22:40, John B. Stephensen wrote:
The digital mode is not dominant as Eagle is to provide simultaneous analog and digital service.>
As far as I can tell, AMSAT has put the linear transponders that the majority of its members wanted on each phase 3 satellite. Adding digital services that the rest of the world is using seems likely to attract more members than continuing with the same old strategy.
73,
John KD6OZH
My dear Mr Stephenson ESQ
There is also a lot of cube sats in the making who will also carry on digital capabilities but for the sake of the AMSAT'S Can we let them carry on a simple satellite where you and me can discuss of you ideas. As you and me are also aware it is not all the satellite community who can use digital modes.
On the rest i agree with you but it seems there is not enough space available in Eagle and i'm afraid many will missed the train. I think P3E will have some sort of digital system.
"-" The medium is the message...The content is the audience...;)
Luc Leblanc VE2DWE WAC basic,CW,Phone,Satellite Skype VE2DWE www.qsl.net/ve2dwe _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
To All,
Finally, leaving Galileo "off the table" right now, I believe Bruce's post gets to the core of what is causing the concern among members. I would hope the Board and the design team gives Bruce's questions due reflection.
The designers and the Board must look to the users for their direction. If users want 145 up and 29 down, and that will satisfy their satellite communications needs, then by golly that's what you put in space even though it isn't technically cute or fashionable. They're the main source of donations (I think unless there are a few well heeled donors with deep pockets driving the ship). In short the Board should be working at the behest of the membership.
Where does all this high duty cycle, high bandwith 256 kbps digital video and text messaging come from anyway? Are we trying to be a cell phone company in space? It neat for sure, but what percentage of our members can make the technical and financial investment for this specialized mode. (This mode wasn't even proposed in the 2004 survey - as read it)
How can I put this nicely? Well, I can't so here goes.
AMSAT should be building satellites that meet majority user requirements not build satellites for the technical ego's of a few.
Ouch - there I said it!
Bruce's suggestion for "user advocates" is good but the organization might well find that it is just another impediment to doing their design work. But no need! The user's spoke in 2004. Perhaps a new user survey is in order - though judging from the comments on the -bb, the opinions have not likely changed.
Regards...Bill - N6GHz
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org]On Behalf Of Bruce Rahn Sent: Friday, September 22, 2006 2:28 PM To: John B. Stephensen Cc: AMSAT BB; K3IO@verizon.net Subject: [amsat-bb] Re: Galileo interference on L band
John B. Stephensen wrote:
Part of the concern about using L as the primary digital uplink is the fact that the ground stations will be high duty cycle emitters. BPSK has a very low crest factor and one of the uses for a 256 kbps link is streaming video, so it will be very much like an ATV repeater. Given the equatorial orbit, Eagle will also be closer to the horizon than previous amateur HEOs.
Even a restriction similar to the one in place for U uplinks in areas of the U.S. (1 kW EIRP) would make high-speed uplinks unavailable.
John,
Thank you for bringing this point to my attention...through my neglect of things I have lost track of the dominance the digital mode has taken in this project. You are correct that this signal format is a high duty cycle one. My thoughts of where Eagle was heading have been more aligned with the desires of the membership expressed in the survey results presented in the September/October 2004 issue of "The AMSAT Journal".
I'm going to ask some hypothetical questions here which I really don't expect you or anyone to answer. They are more food for thought than anything else.
- As part of the system engineering process, were other bit rates and modulation schemes considered which would mitigate potential interference problems?
- What percentage of the user base (AMSAT-NA members) would be disenfranchised if digital video were eliminated because of its high duty cycle requirements and the potential for causing interference to other spectrum users?
- In the aforementioned survey results, the surveyed members indicated their highest preference was for analog modes followed in second place by digital. Has the user mindset shifted to digital over analog? If not, or unknown, are the spacecraft resources being fairly partitioned and allocated to support analog users? What percentage of the user community will be using digital video and text messaging?
In a private exchange with Mr. Sanford, I expressed my concern that the user community was not being represented by a strong 'user advocate' at critical design meetings. 'Designers are not users and users are not designers' but both camps must be fairly represented to achieve harmony and consensus between the two. Bringing a strong 'user advocate' into the design process would be a win-win situation for both the user community as well as the design community. Users would feel someone is directly addressing their operational concerns and the 'user advocate' could be the one defending decisions rather than occupying the time of the designers in addressing these concerns.
I believe in the 20 plus years I have been an AMSAT member history has demonstrated that the 'if we build it they will come' approach has not worked well. Had it been successful, the organization would have more resources in terms of members and dollars than we could deal with.
Respectfully -- Bruce
-- Bruce Rahn
Wisdom has two parts: 1. having a lot to say; and 2. not saying it!
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Mode B (U/V) and J (V/U) were the first and second most popular modes for the membership and 65% were interested in a digital phase 3 satellite. SSB (class 0) and the digital mode that fits (class 1) will be available on U/V. V/U is plagued by interference in some areas of the world.
73,
John KD6OZH
----- Original Message ----- From: "Bill Ress" bill@hsmicrowave.com To: brahn@woh.rr.com; "John B. Stephensen" kd6ozh@comcast.net Cc: "AMSAT BB" amsat-bb@amsat.org; K3IO@verizon.net Sent: Friday, September 22, 2006 23:02 UTC Subject: RE: [amsat-bb] Re: Galileo interference on L band
To All,
Finally, leaving Galileo "off the table" right now, I believe Bruce's post gets to the core of what is causing the concern among members. I would hope the Board and the design team gives Bruce's questions due reflection.
The designers and the Board must look to the users for their direction. If users want 145 up and 29 down, and that will satisfy their satellite communications needs, then by golly that's what you put in space even though it isn't technically cute or fashionable. They're the main source of donations (I think unless there are a few well heeled donors with deep pockets driving the ship). In short the Board should be working at the behest of the membership.
Where does all this high duty cycle, high bandwith 256 kbps digital video and text messaging come from anyway? Are we trying to be a cell phone company in space? It neat for sure, but what percentage of our members can make the technical and financial investment for this specialized mode. (This mode wasn't even proposed in the 2004 survey - as read it)
How can I put this nicely? Well, I can't so here goes.
AMSAT should be building satellites that meet majority user requirements not build satellites for the technical ego's of a few.
Ouch - there I said it!
Bruce's suggestion for "user advocates" is good but the organization might well find that it is just another impediment to doing their design work. But no need! The user's spoke in 2004. Perhaps a new user survey is in order - though judging from the comments on the -bb, the opinions have not likely changed.
Regards...Bill - N6GHz
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org]On Behalf Of Bruce Rahn Sent: Friday, September 22, 2006 2:28 PM To: John B. Stephensen Cc: AMSAT BB; K3IO@verizon.net Subject: [amsat-bb] Re: Galileo interference on L band
John B. Stephensen wrote:
Part of the concern about using L as the primary digital uplink is the fact that the ground stations will be high duty cycle emitters. BPSK has a very low crest factor and one of the uses for a 256 kbps link is streaming video, so it will be very much like an ATV repeater. Given the equatorial orbit, Eagle will also be closer to the horizon than previous amateur HEOs.
Even a restriction similar to the one in place for U uplinks in areas of the U.S. (1 kW EIRP) would make high-speed uplinks unavailable.
John,
Thank you for bringing this point to my attention...through my neglect of things I have lost track of the dominance the digital mode has taken in this project. You are correct that this signal format is a high duty cycle one. My thoughts of where Eagle was heading have been more aligned with the desires of the membership expressed in the survey results presented in the September/October 2004 issue of "The AMSAT Journal".
I'm going to ask some hypothetical questions here which I really don't expect you or anyone to answer. They are more food for thought than anything else.
- As part of the system engineering process, were other bit rates and
modulation schemes considered which would mitigate potential interference problems?
- What percentage of the user base (AMSAT-NA members) would be
disenfranchised if digital video were eliminated because of its high duty cycle requirements and the potential for causing interference to other spectrum users?
- In the aforementioned survey results, the surveyed members indicated
their highest preference was for analog modes followed in second place by digital. Has the user mindset shifted to digital over analog? If not, or unknown, are the spacecraft resources being fairly partitioned and allocated to support analog users? What percentage of the user community will be using digital video and text messaging?
In a private exchange with Mr. Sanford, I expressed my concern that the user community was not being represented by a strong 'user advocate' at critical design meetings. 'Designers are not users and users are not designers' but both camps must be fairly represented to achieve harmony and consensus between the two. Bringing a strong 'user advocate' into the design process would be a win-win situation for both the user community as well as the design community. Users would feel someone is directly addressing their operational concerns and the 'user advocate' could be the one defending decisions rather than occupying the time of the designers in addressing these concerns.
I believe in the 20 plus years I have been an AMSAT member history has demonstrated that the 'if we build it they will come' approach has not worked well. Had it been successful, the organization would have more resources in terms of members and dollars than we could deal with.
Respectfully -- Bruce
-- Bruce Rahn
Wisdom has two parts:
- having a lot to say; and
- not saying it!
Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Hi Tom,
You stated:
"Sorry -- I've been away from home on business while the latest flack occurred under the general topic heading "Galileo interference on L band"."
First, I would hope we could characterize the past proceedings on the -bb as a useful debate rather than "flack."
That said, I do appreciate your links on interference which I have read previously but they can be useful to others following this discussion.
But perhaps my conclusions, after reading the links, might differ from yours. But, I think we can agree, as I have stated before, that a potential for interference "could" possibly exist, albeit, at some future time.
The key issue here for us the use of the Amateur satellite L-Band 1260 to 1270 Mhz.
The articles you reference deal primarily with interference to G2 GLONOSS which operates at 1240 to 1256. One of the interfering signals the articles point out are German Digipeaters operating in the (authorized) frequency range of 1240 to 1242 Mhz (the low end of the G2 band).
That material was published in 1999. While I don't have the answer, maybe you do, the question to ask is: in the seven intervening years has there been any GLONOSS or GPS "public safety" issues resulting from the Digipeater operations, and have these Digipeaters since been taken off the air by the regulatory agencies?
I believe the articles also hit heavy on the ATC radar interference in Germany (and likely elsewhere). Do we know if any of the ATC radars have moved in frequency?
The articles also point out interference deficiencies in several of the receivers tested and alludes to ways of mitigating their deficiencies. I'm sure that over the past seven years receiver improvements have been made.
You also said:
"We the Eagle technical team, have never said that L-band won't work NOW or 5 years from now. But our vision for Eagle is that when the first one flies 4-5 years from now, we want it to be a useful resource for at least a 10 year lifetime. We are very concerned about making a several million dollar (after you count the volunteer builder's blood, sweat & tears) investment only to have it blown away right after launch by the GNSS cartels just because we picked L-band to be anything like a "primary" uplink."
Yes - those are admirable desires but we can't engineer for "unknown" future events. It just bogs us down with worry that we might not make the right "guess." Instead, as I stated before, base decisions on the engineering facts as we know them today (available technology, size, power, space, resources, user needs, etc.) and let the future bring on whatever it has in store for us.
If you can make arguments that L-Band won't work because of system engineering constraints or the mission objectives we have before us today - I can live with that. But lets take this Galileo "cloud" off the decision process.
I don't think many future AMSAT communicators will fault you for not being able to predict the future.
Regards...Bill - N6GHz
_______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
Bill,
... we can't engineer for "unknown" future events.
The L-band issues under discussion are not unknown. The impacts and regulatory remedies for the Galileo community against Hams are uncertain, knot unknown.
It just bogs us down with worry that we might not make the right "guess."
No one is bogged down. The Eagle design team is weighing the issues associated with each possible choice of uplinks and downlinks to maximize the utility of Eagle to the largest community of users possible. The debates on amsat-bb do not slow down the design process, although occasionally they do provide interesting material for consideration.
... base decisions on the engineering facts as we know them today ... and let the future bring on whatever it has in store for us.
That would be an irresponsible thing for AMSAT leadership to allow, and the Eagle project team knows it. To launch a high orbit satellite takes resources that stretch the capability of the Ham community to the limit. We must maximize the probability of a successful mission.
If you can make arguments that L-Band won't work ...
We are getting way off track here. No one is saying L-band won't work, now or in the future. What we are saying is that there has been some evidence to suggest that we could loose access to the band if "a" or "b" or "c" happens. This creates a concern that needs to be factored into the evaluation of the alternatives for Eagle.
But lets take this Galileo "cloud" off the decision process.
I repeat that this would be an irresponsible decision. What needs to be done is to evaluate this and other threats, which are largely out of our control, and integrate the treats and their mitigation into our decision making process.
I don't think many future AMSAT communicators will fault you for not being able to predict the future.
Really? I assure you that if we make a conscious decision to ignore an important issue and we turned out to be wrong there would be a massive campaign of criticism.
I predict that there will be multiple L-band uplinks and an S-band downlink on Eagle; they just won't be primary links. Whatever the outcome, the decisions will be based on the best information available to the Eagle project team, including inputs from the international community. They will also be based on the need to attract new young Hams to satellites so our future is secure.
Some of the people debating the issues on amsat-bb impress me as possibly qualified to participate directly in AMSAT projects or in other responsible roles. We have openings and I encourage you to contact your AMSAT officers and introduce yourself if you would like to volunteer you time and talent to the advancement of Ham Radio.
Rick W2GPS AMSAT LM2232
At 02:54 AM 9/22/2006, Bill Ress wrote:
Yes - those are admirable desires but we can't engineer for "unknown" future events. It just bogs us down with worry that we might not make the right "guess." Instead, as I stated before, base decisions on the engineering facts as we know them today (available technology, size, power, space, resources, user needs, etc.) and let the future bring on whatever it has in store for us.
If you can make arguments that L-Band won't work because of system engineering constraints or the mission objectives we have before us today - I can live with that. But lets take this Galileo "cloud" off the decision process.
Bill: I think one of the problems still is how to get a large enough L-band gain antenna on the satellite so that the ground station antennas don't end up being huge. If I got that wrong, perhaps Bob McGwier and the team could correct me. If we cannot get a high gain system with reasonable beam-width (steerable vs. non-steerable) on the satellite, then the ground station antenna might be unwieldy compared to the higher frequencies.
Again, I may have misunderstood this point, so I could easily stand corrected.
Dave
Hi Dave,
That's a very good valid point! You see, its the technical issues like this I'd like to see debated and considered, not considerations made for the "unknown or uncertain."
If the L-Band antenna size needed causes compromises for some other more primary mission requirements, then the decision is easy. L-Band goes and I can live with that.
The future uncertain state of frequency allocations is one that I would have difficulty designing for today. "ALL" of our satellite allocations up to 24Ghz are on a "secondary" basis. That makes them fair game for interference from and to primary users and changes by regulatory bodies.
With that "uncertainty" in mind, do we jump up to 24GHz for our transponders where we're primary. Not a real good idea but we'd sure eliminate all this WiFi, Galileo discussion - at least until some commercial endeavor jumps on 24 GHz with a "killer" money making application and we're back to the "uncertain" all over again.
So when it comes to our below 24 GHz frequency allocations we should design for mitigations (co-existence) not abandonment.
But, it appears that the Eagle team, according to Rick's last post, will have L and S capabilities consistent with the overall mission requirements and that's a positive thing.
Regards...Bill - N6GHz
-----Original Message----- From: David B. Toth [mailto:ve3gyq@amsat.org] Sent: Friday, September 22, 2006 9:59 AM To: Bill Ress; AMSAT BB Subject: Re: [amsat-bb] Re: Galileo interference on L band
At 02:54 AM 9/22/2006, Bill Ress wrote:
Yes - those are admirable desires but we can't engineer for "unknown"
future
events. It just bogs us down with worry that we might not make the right "guess." Instead, as I stated before, base decisions on the engineering facts as we know them today (available technology, size, power, space, resources, user needs, etc.) and let the future bring on whatever it has in store for us.
If you can make arguments that L-Band won't work because of system engineering constraints or the mission objectives we have before us today - I can live with that. But lets take this Galileo "cloud" off the decision process.
Bill: I think one of the problems still is how to get a large enough L-band gain antenna on the satellite so that the ground station antennas don't end up being huge. If I got that wrong, perhaps Bob McGwier and the team could correct me. If we cannot get a high gain system with reasonable beam-width (steerable vs. non-steerable) on the satellite, then the ground station antenna might be unwieldy compared to the higher frequencies.
Again, I may have misunderstood this point, so I could easily stand corrected.
Dave
We don't have time to answer all of these questions now. We are preparing decision notices for the Eagle team, briefings and recommendations for the BOD, because we go to the annual meeting in 3 weeks! I barely have time to write all of this work down. Go away for 3 weeks. Once you hear the recommendations and their completed justification, then cry or laugh, applaud or throw stones. Just let me say my U/V/L/S gear is all well protected and is not going on the market for sale. As I have already said, the FLACK (I will use it with emphasis since that is how I view it) is very premature.
Now go away.
Bob
Snip!
As I have already said, the FLACK (I will use it with emphasis since that is how I view it) is very premature.
Now go away.
Bob
snip!
Dear Bob, you left out Thanks for the Votes Suckers
Signed Cordially Your Newly Elected BOD
LOL Kevin
participants (14)
-
Arthur Feller -
Bill Ress -
Bruce Rahn -
Bruce Robertson -
David B. Toth -
Edward R. Cole -
George Henry -
John B. Stephensen -
Luc Leblanc VE2DWE -
Rick Hambly (W2GPS) -
Robert McGwier -
sco＠sco-inc.com -
Tom Clark, K3IO -
wa6fwf