Where we're heading for bands and services
Team:
The Eagle Chief Technology Officer (W2GPS), the AMSAT VP Engineering
(N4HY) and I met (electronically) to discuss the Eagle payload complement.
We have decided the following should be our recommendation to the board of
directors of AMSAT for their ratification. This is what will be presented to the BoD:
1. Services to be provided, as defined at the San Diego meeting et seq:
Class 0 is linear transponder users
Class 1 is SMS text message service users
Class 2 is weak signal voice grade digital channel
Class 3 is strong signal, large antenna, higher bandwidth signal (think
compressed full motion video)
2. Primary class 0 payload: U/V with a design goal that it be usable over
75% of the orbit.
3. Primary class 1 payload: U/V for the reasons discussed at San Diego.
3. Primary Class 2 and 3 ACP payload: S2/C usable over 75% of the orbit. This
coverage to be accomplished by using electronically de-spun phased arrays on S2 and C.
At San Diego, we discussed S2 vs. S1. S2 was technically superior, but other issues
caused us to shy away from it. Upon reflection, the leadership has decided to proceed down the technically superior path, S2 uplink.
4. Secondary Class 0 payload: L/S1 -if and when the power budget and
antenna pointing (fixed, nadir-pointing array) can support. We recognize that it may not be usable
in many areas due to elevated noise floor resulting from 802.xx devices, as discussed in San
Diego and documented in measurements and analysis.
NO PERFORMANCE LEVEL IS TO BE PROMISED.
5. Secondary ACP Class 2 uplink: A separate L receiver feeding same DSP and C-band
downlink when fixed nadir-pointing antenna array supports. This second receiver will share
the L-band LNA and antenna with the L/S1 Class 0 payload.
The greater level of service for S2 users should encourage people who can to use S2 rather than L.
NO PERFORMANCE LEVEL IS TO BE PROMISED.
6. Use of all secondary payloads will be subject to acceptable costs in power, heat, and/or mass,
as assessed by analysis or testing. They are to be turned off if regulatory constraints are
imposed post launch. They will not be flown at all if shown to be not feasible through
analysis or testing.
This is what I will present to the board at Symposium for their concurrence. Please contain this discussion within the Eagle team until the Board makes a decision.
I request your comments within the next 48 hours so that I can finish the budget tonight and begin
crafting my presentation to the board and my follow-on presentation at Symposium. We need to bring this to closure so that we can present decisions at Symposium, and move out smartly from there. Thanks.
Very 73,
Jim
wb4gcs@amsat.org mailto:wb4gcs@amsat.org
UNQUOTE
Thank you Jim.
John, if you would, please transmit your antenna concept drawing to the group. I really like it.
When I answered Rick's proposal for an L band uplink in our decision meeting, I suggested that we do it with a 200 kHz limit and that final bandwidth is to be determined by calculation. I suggest we base the IF for the L band input to the ACP on QSD. It is a high dynamic range, low power mixer. We can digitize that with audio A/D's running pretty low power and send I/Q to the ACP/DSP. This will give Region 1 a few uplinks to the ACP.
On L band we need the SDX pick off, the ACP pick off, and the command receiver pick off using a single antenna and any LNA.
My first reaction to John's subsequent block diagram was that the switching arrangement is complex and I did not understand the need for some of the lines in it.
S2/C is a technical win over S1/C because of the smaller antenna area on the spacecraft (18 dBi fixed design) and giving us the ability to separate the two antennas. John and I discussed the spin doppler caused by the offset patches. It will be insignificant. The noise floor at the satellite on 3.4 should be considerably less than S2 and with the "region 1" input, where we should require Class 3 EIRP or thereabouts, allows them to use the facility.
I have really enjoyed all of the debate, design meetings, and ideas but I like coming to a place where we can begin to design hardware and the services. We really do need a launch to focus on. Those efforts are ongoing and probably will be for a while.
Bob N4HY
Jim Sanford wrote:
Team:
The Eagle Chief Technology Officer (W2GPS), the AMSAT VP Engineering (N4HY) and I met (electronically) to discuss the Eagle payload complement.
We have decided the following should be our recommendation to the board of directors of AMSAT for their ratification. This is what will be presented to the BoD:
- Services to be provided, as defined at the San Diego meeting et seq: Class 0 is linear transponder users Class 1 is SMS text message service users Class 2 is weak signal voice grade digital channel Class 3 is strong signal, large antenna, higher bandwidth signal (think compressed full motion video)
--- snip --
Very 73, Jim wb4gcs@amsat.org mailto:wb4gcs@amsat.org
If we don't "promise" a performance level, then we must face the problem that Franklin pointed out with AO-40 -- a set of realistic user requirements was never presented, so everyone was just flying blind.
I think we need to promise a field strength (flux density, whatever the politically correct term is these days :-) on the ground for a given uplink power by the user, or its equivalent. We can't control the user's noise environment, but we sure better be able to predict our downlink and publish it and meet it. And don't forget to add 6 to 8 dB of loss just because, since I seem to recall we've nearly always been 6 to 8 dB shy of our expectatins in the past...
73,
Lyle KK7P
Lyle Johnson wrote:
If we don't "promise" a performance level, then we must face the problem that Franklin pointed out with AO-40 -- a set of realistic user requirements was never presented, so everyone was just flying blind.
I think we need to promise a field strength (flux density, whatever the politically correct term is these days :-) on the ground for a given uplink power by the user, or its equivalent. We can't control the user's noise environment, but we sure better be able to predict our downlink and publish it and meet it. And don't forget to add 6 to 8 dB of loss just because, since I seem to recall we've nearly always been 6 to 8 dB shy of our expectatins in the past...
73,
Lyle KK7P
This is misunderstood. No promised performance level means "We are not promising this will work over 70+% of the orbit and with a few watt station to a 0.6m dish". Not as in "we ain't even gonna measure it". All performances are to be measured. The L performance goal is "best achievable within the constraints".
Bob
Robert McGwier wrote:
Thank you Jim.
John, if you would, please transmit your antenna concept drawing to the group. I really like it.
When I answered Rick's proposal for an L band uplink in our decision meeting, I suggested that we do it with a 200 kHz limit and that final bandwidth is to be determined by calculation. I suggest we base the IF for the L band input to the ACP on QSD. It is a high dynamic range, low power mixer. We can digitize that with audio A/D's running pretty low power and send I/Q to the ACP/DSP. This will give Region 1 a few uplinks to the ACP.
ACP?
On L band we need the SDX pick off, the ACP pick off, and the command receiver pick off using a single antenna and any LNA.
By "the command receiver" do you mean a fixed frequency demodulator output for the IHU3?
My first reaction to John's subsequent block diagram was that the switching arrangement is complex and I did not understand the need for some of the lines in it.
S2/C is a technical win over S1/C because of the smaller antenna area on the spacecraft (18 dBi fixed design) and giving us the ability to separate the two antennas. John and I discussed the spin doppler caused by the offset patches. It will be insignificant. The noise floor at the satellite on 3.4 should be considerably less than S2 and with the "region 1" input, where we should require Class 3 EIRP or thereabouts, allows them to use the facility.
I discussed some of these ideas with Eric, N7CL, at the TAPR meeting. Eric is very good at antenna system design, did S band stuff for us at MMS and does this sort of thing now for DoD.
Anyway, he suggested we consider Vivaldi's rather than patches. We used Vivaldi's on our trucks at S Band and they work well, are trivial to fabricate (a piece of PC board - I know, radiation, but it is the concept I am wanting us to consider). They are well behaved and have very little coupling to adjacent antennas. I'm not an antenna guy, but you might want to consider the Vivaldi and/or communicate with Eric.
Lyle
I have really enjoyed all of the debate, design meetings, and ideas but I like coming to a place where we can begin to design hardware and the services. We really do need a launch to focus on. Those efforts are ongoing and probably will be for a while.
Bob N4HY
Jim Sanford wrote:
Team:
The Eagle Chief Technology Officer (W2GPS), the AMSAT VP Engineering (N4HY) and I met (electronically) to discuss the Eagle payload complement.
We have decided the following should be our recommendation to the board of directors of AMSAT for their ratification. This is what will be presented to the BoD:
- Services to be provided, as defined at the San Diego meeting et seq: Class 0 is linear transponder users Class 1 is SMS text message service users Class 2 is weak signal voice grade digital channel Class 3 is strong signal, large antenna, higher bandwidth signal (think compressed full motion video)
--- snip --
Very 73, Jim wb4gcs@amsat.org mailto:wb4gcs@amsat.org
Lyle Johnson wrote:
I discussed some of these ideas with Eric, N7CL, at the TAPR meeting. Eric is very good at antenna system design, did S band stuff for us at MMS and does this sort of thing now for DoD.
Anyway, he suggested we consider Vivaldi's rather than patches. We used Vivaldi's on our trucks at S Band and they work well, are trivial to fabricate (a piece of PC board - I know, radiation, but it is the concept I am wanting us to consider). They are well behaved and have very little coupling to adjacent antennas. I'm not an antenna guy, but you might want to consider the Vivaldi and/or communicate with Eric.
Eric also assisted me with the design of the Microsat 2M rcvrs -- which bore a strange similarity to an MMS design.
AFAIK, the Vivaldi and antipodal antennas are linearly polarized. Multiple elements require crossed antennas, like Fig.9 in http://www.ansoft.com/news/articles/04.09a_MWJ.pdf#search=%22vivaldi%20anten... (note that the radiation is "endfire").
A PhD thesis for a 2-8 GHz describing this antenna used for a Snow radar is seen at http://profusion.ittc.ku.edu/research/thesis/documents/ravi_prakash_rajarama.... Also, to see what an array of these devices might look like, see http://nemes.colorado.edu/microwave/papers/2000/APS_JPWbn_00.pdf#search=%22v... (in this case, the SKA is a concept design for an SKA=square-kilometer array for radio astronomy. Many different approaches are being studied ranging from a field full of tens of thousands of patch antennas, each equipped with signal processing "smarts" to arrays of a hundreds of dishes. See http://www.skatelescope.org/ for more info)
73, Tom
Tom Clark, K3IO wrote:
Lyle Johnson wrote:
I discussed some of these ideas with Eric, N7CL, at the TAPR meeting. Eric is very good at antenna system design, did S band stuff for us at MMS and does this sort of thing now for DoD.
Anyway, he suggested we consider Vivaldi's rather than patches. We used Vivaldi's on our trucks at S Band and they work well, are trivial to fabricate (a piece of PC board - I know, radiation, but it is the concept I am wanting us to consider). They are well behaved and have very little coupling to adjacent antennas. I'm not an antenna guy, but you might want to consider the Vivaldi and/or communicate with Eric.
Eric also assisted me with the design of the Microsat 2M rcvrs -- which bore a strange similarity to an MMS design.
AFAIK, the Vivaldi and antipodal antennas are linearly polarized. Multiple elements require crossed antennas, like Fig.9 in http://www.ansoft.com/news/articles/04.09a_MWJ.pdf#search=%22vivaldi%20anten... (note that the radiation is "endfire").
A PhD thesis for a 2-8 GHz describing this antenna used for a Snow radar is seen at http://profusion.ittc.ku.edu/research/thesis/documents/ravi_prakash_rajarama....
Having read the papers my first quickest impressions are
1) The vivaldi is attempting to solve a problem we do not have. We are not after an antenna that exhibits gain, low return loss, polarization isolation, etc. over several GHz. 2) It has gain a little lower than a vacuum dielectric patch at 4 dBi versus 6 dBi of our circular patches or cross dipoles or whatever. We have built in implementation loss in our calculations but I hate to give it up immediately. We would have to have 50% more area to make up for the lost gain over the patches with the increase complexity of feeding, etc. 3) I dont' know what substrate we could use that we could fly outside the spacecraft but we might be able to recess it into the structure in a tube and that would certainly reduce mutual coupling. What else it would do, is beyond my EM theory to guess. 4) It is a traveling wave antenna and/or end fire and according to recent authors "it is not well understood".
I am not rejecting them just giving my first impressions which might even be wrong but they are my first impressions.
Off to the salt mines Bob
Lyle Johnson wrote:
Robert McGwier wrote:
Thank you Jim.
ACP?
Advanced Communications Package (to be read: Hambly Marketing Firm, Inc. does not want us calling it Digital).
On L band we need the SDX pick off, the ACP pick off, and the command receiver pick off using a single antenna and any LNA.
By "the command receiver" do you mean a fixed frequency demodulator output for the IHU3?
Yes. A fixed frequency separate input not in the passband. I can hear James Miller in my head : "We shan't have the punters confiscating the command channel".
I discussed some of these ideas with Eric, N7CL, at the TAPR meeting. Eric is very good at antenna system design, did S band stuff for us at MMS and does this sort of thing now for DoD.
Anyway, he suggested we consider Vivaldi's rather than patches. We used Vivaldi's on our trucks at S Band and they work well, are trivial to fabricate (a piece of PC board - I know, radiation, but it is the concept I am wanting us to consider). They are well behaved and have very little coupling to adjacent antennas. I'm not an antenna guy, but you might want to consider the Vivaldi and/or communicate with Eric.
I don't know what a Vivaldi is but I will find out.
Lyle
Bob N4HY
By "the command receiver" do you mean a fixed frequency demodulator output for the IHU3?
Yes. A fixed frequency separate input not in the passband. I can hear James Miller in my head : "We shan't have the punters confiscating the command channel". --------------------------------------
But if the punters are saturating the L Rx front end, the commanding cannot get through to the decoder.
Dick, WD4FAB
Dick Jansson-rr wrote:
By "the command receiver" do you mean a fixed frequency demodulator output for the IHU3?
Yes. A fixed frequency separate input not in the passband. I can hear James Miller in my head : "We shan't have the punters confiscating the command channel".
But if the punters are saturating the L Rx front end, the commanding cannot get through to the decoder.
Dick, WD4FAB
Dick,
For this reason I totally separated IF chain for usesrs and for commands. The AGC influences only user's outputs. The command receiver contains own filter shifted to the passband and works as limiting.
Mirek
Indeed. Mirek has done it correctly in my opinion.
Bob
Miroslav Kasal wrote:
Dick Jansson-rr wrote:
By "the command receiver" do you mean a fixed frequency demodulator output for the IHU3?
Yes. A fixed frequency separate input not in the passband. I can hear James Miller in my head : "We shan't have the punters confiscating the command channel".
But if the punters are saturating the L Rx front end, the commanding cannot get through to the decoder.
Dick, WD4FAB
Dick,
For this reason I totally separated IF chain for usesrs and for commands. The AGC influences only user's outputs. The command receiver contains own filter shifted to the passband and works as limiting.
Mirek
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Here is the drawing. The V antenna (3 dipoles) and the U antenna (crossed dipoles) are centered on the spin axis as the class 1 service is the most sensitive to spin modulation. The L, S1, S2 and C antennas are then arrayed around the U antenna. I used 4 patches for the L and S1 antennas as they may disrupt the U antenna pattern less than helices. Since an S2 array is 50% smaller than an S1 array, a 32 or 36 element array will fit nicely between the U and V antennas.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" rwmcgwier@comcast.net To: "Jim Sanford" wb4gcs@amsat.org Cc: "'AMSAT Eagle'" Eagle@amsat.org Sent: Monday, September 25, 2006 01:26 UTC Subject: [eagle] Re: Where we're heading for bands and services
Thank you Jim.
John, if you would, please transmit your antenna concept drawing to the group. I really like it.
When I answered Rick's proposal for an L band uplink in our decision meeting, I suggested that we do it with a 200 kHz limit and that final bandwidth is to be determined by calculation. I suggest we base the IF for the L band input to the ACP on QSD. It is a high dynamic range, low power mixer. We can digitize that with audio A/D's running pretty low power and send I/Q to the ACP/DSP. This will give Region 1 a few uplinks to the ACP.
On L band we need the SDX pick off, the ACP pick off, and the command receiver pick off using a single antenna and any LNA.
My first reaction to John's subsequent block diagram was that the switching arrangement is complex and I did not understand the need for some of the lines in it.
S2/C is a technical win over S1/C because of the smaller antenna area on the spacecraft (18 dBi fixed design) and giving us the ability to separate the two antennas. John and I discussed the spin doppler caused by the offset patches. It will be insignificant. The noise floor at the satellite on 3.4 should be considerably less than S2 and with the "region 1" input, where we should require Class 3 EIRP or thereabouts, allows them to use the facility.
I have really enjoyed all of the debate, design meetings, and ideas but I like coming to a place where we can begin to design hardware and the services. We really do need a launch to focus on. Those efforts are ongoing and probably will be for a while.
Bob N4HY
Jim Sanford wrote:
Team:
The Eagle Chief Technology Officer (W2GPS), the AMSAT VP Engineering (N4HY) and I met (electronically) to discuss the Eagle payload complement.
We have decided the following should be our recommendation to the board of directors of AMSAT for their ratification. This is what will be presented to the BoD:
- Services to be provided, as defined at the San Diego meeting et seq: Class 0 is linear transponder users Class 1 is SMS text message service users Class 2 is weak signal voice grade digital channel Class 3 is strong signal, large antenna, higher bandwidth signal
(think compressed full motion video)
--- snip --
Very 73, Jim wb4gcs@amsat.org mailto:wb4gcs@amsat.org
-- AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman "You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat." - Einstein
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
If we are still planning on two SDXs, we'll need 4 pickoffs on the L receiver. The required uplink power on L-band can be generated with existing amateur-band antenna and amplifier products for both class 2 and class 3. Most of the lines in the diagram are to allow either SDX to use any receiver and any transmitter. Which lines seem unnecessary?
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" rwmcgwier@comcast.net To: "Jim Sanford" wb4gcs@amsat.org Cc: "'AMSAT Eagle'" Eagle@amsat.org Sent: Monday, September 25, 2006 01:26 UTC Subject: [eagle] Re: Where we're heading for bands and services
Thank you Jim.
John, if you would, please transmit your antenna concept drawing to the group. I really like it.
When I answered Rick's proposal for an L band uplink in our decision meeting, I suggested that we do it with a 200 kHz limit and that final bandwidth is to be determined by calculation. I suggest we base the IF for the L band input to the ACP on QSD. It is a high dynamic range, low power mixer. We can digitize that with audio A/D's running pretty low power and send I/Q to the ACP/DSP. This will give Region 1 a few uplinks to the ACP.
On L band we need the SDX pick off, the ACP pick off, and the command receiver pick off using a single antenna and any LNA.
My first reaction to John's subsequent block diagram was that the switching arrangement is complex and I did not understand the need for some of the lines in it.
S2/C is a technical win over S1/C because of the smaller antenna area on the spacecraft (18 dBi fixed design) and giving us the ability to separate the two antennas. John and I discussed the spin doppler caused by the offset patches. It will be insignificant. The noise floor at the satellite on 3.4 should be considerably less than S2 and with the "region 1" input, where we should require Class 3 EIRP or thereabouts, allows them to use the facility.
I have really enjoyed all of the debate, design meetings, and ideas but I like coming to a place where we can begin to design hardware and the services. We really do need a launch to focus on. Those efforts are ongoing and probably will be for a while.
Bob N4HY
Jim Sanford wrote:
Team:
The Eagle Chief Technology Officer (W2GPS), the AMSAT VP Engineering (N4HY) and I met (electronically) to discuss the Eagle payload complement.
We have decided the following should be our recommendation to the board of directors of AMSAT for their ratification. This is what will be presented to the BoD:
- Services to be provided, as defined at the San Diego meeting et seq: Class 0 is linear transponder users Class 1 is SMS text message service users Class 2 is weak signal voice grade digital channel Class 3 is strong signal, large antenna, higher bandwidth signal
(think compressed full motion video)
--- snip --
Very 73, Jim wb4gcs@amsat.org mailto:wb4gcs@amsat.org
-- AMSAT VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP/AMQRP, QRP ARCI, QCWA, FRC. ARRL SDR Wrk Grp Chairman "You see, wire telegraph is a kind of a very, very long cat. You pull his tail in New York and his head is meowing in Los Angeles. Do you understand this? And radio operates exactly the same way: you send signals here, they receive them there. The only difference is that there is no cat." - Einstein
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
I STRONGLY suggest that you NOT use terms like "Class 0". It's bad enough having classes, but 0 is demeaning. and will be taken as such by those you consider in that class.
If you MUST use terms like "class", you might call Class 0, Class A, Class 1, Class B etc. That, at least sounds better and should help with fund raising.
73,
Bill ----- Original Message ----- From: Jim Sanford To: 'AMSAT Eagle' Sent: Sunday, September 24, 2006 7:36 PM Subject: [eagle] Where we're heading for bands and services
Team: The Eagle Chief Technology Officer (W2GPS), the AMSAT VP Engineering (N4HY) and I met (electronically) to discuss the Eagle payload complement. We have decided the following should be our recommendation to the board of directors of AMSAT for their ratification. This is what will be presented to the BoD: 1. Services to be provided, as defined at the San Diego meeting et seq: Class 0 is linear transponder users Class 1 is SMS text message service users Class 2 is weak signal voice grade digital channel Class 3 is strong signal, large antenna, higher bandwidth signal (think compressed full motion video) 2. Primary class 0 payload: U/V with a design goal that it be usable over 75% of the orbit. 3. Primary class 1 payload: U/V for the reasons discussed at San Diego. 3. Primary Class 2 and 3 ACP payload: S2/C usable over 75% of the orbit. This coverage to be accomplished by using electronically de-spun phased arrays on S2 and C. At San Diego, we discussed S2 vs. S1. S2 was technically superior, but other issues caused us to shy away from it. Upon reflection, the leadership has decided to proceed down the technically superior path, S2 uplink. 4. Secondary Class 0 payload: L/S1 -if and when the power budget and antenna pointing (fixed, nadir-pointing array) can support. We recognize that it may not be usable in many areas due to elevated noise floor resulting from 802.xx devices, as discussed in SanDiego and documented in measurements and analysis. NO PERFORMANCE LEVEL IS TO BE PROMISED. 5. Secondary ACP Class 2 uplink: A separate L receiver feeding same DSP and C-band downlink when fixed nadir-pointing antenna array supports. This second receiver will share the L-band LNA and antenna with the L/S1 Class 0 payload.The greater level of service for S2 users should encourage people who can to use S2 rather than L. NO PERFORMANCE LEVEL IS TO BE PROMISED. 6. Use of all secondary payloads will be subject to acceptable costs in power, heat, and/or mass,as assessed by analysis or testing. They are to be turned off if regulatory constraints are imposed post launch. They will not be flown at all if shown to be not feasible through analysis or testing. This is what I will present to the board at Symposium for their concurrence. Please contain this discussion within the Eagle team until the Board makes a decision. I request your comments within the next 48 hours so that I can finish the budget tonight and begin crafting my presentation to the board and my follow-on presentation at Symposium. We need to bring this to closure so that we can present decisions at Symposium, and move out smartly from there. Thanks. Very 73,Jimwb4gcs@amsat.orgUNQUOTE
------------------------------------------------------------------------------
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
participants (8)
-
Bill Tynan -
Dick Jansson-rr -
Jim Sanford -
John B. Stephensen -
Lyle Johnson -
Miroslav Kasal -
Robert McGwier -
Tom Clark, K3IO