All: I send this separate note to advise you of some major developments with Eagle. Many of you are already aware of them, but in case I missed someone, I send this separate update.
Two nights ago, I authorized expenditure of funds for purchase of components and construction of four prototypes of the UHF receiver designed by John Stephenson, KD6OZH. The boards will be distributed as follows: one to Juan Rivera, WA6HTP, for Acceptance Testing followed by limited vacuum and thermal testing one to be demonstrated at Dayton one to the SDX folks for their development one to be put through the ATP either here by me, or wherever anyone else wants to evaluate. This will then become available as needed for demonstrations or SDX development
Events leading to this decision: Design by John and Peer review Development of ATP by Juan and peer review Assembly of a procurement, construction, and test team of Project Oscar members under Juan's leadership PCBoard layout by John. Peer review of schematic to board correlation in progress Development of costed Bill of Materials (BOM) by the Project Oscar team. This was a LOT of work, and actually resulted in some tweaks to design and component selection Peer review of the BOM in progress
I have authorized $4100 for this effort. A small fraction of this cost includes consumables for surface mount construction and some assembly tools which will become AMSAT property and will be used again. AMSAT costs were reduced by a significant amount of "scrounging."
I submitted some of this information for publication in ANS, but don't yet know if I was ahead of the deadline or not.. If I was late, I hope it will appear next week.
This seems to me a huge step. We have completed one design cycle on one component and are now about to transition, for that one component, from the concept exploration/definition phase into construction of hardware. Prototype hardware, yes, but we will soon have some real test results and something real to show. The short list above belies a whole lot of work by a whole lot of folks, alll of whom I thank. Many of you participated in the earlier reviews of John's design and Juan's ATP. The near-frantic effort over the last few weeks by John and the Project Oscar folks (many of whom I'm just getting to know through various emails and echolink conferences) has been intense.
As we progress with procurement and construction, I will receive and share progress updates as major milestones are met.
The documents mentioned above are not all on EaglePedia yet, but will be. In particular, one unexpected fallout of the recent efforts is a BOM which may be a good template for other teams to use. It certainly made it easy for me to see and understand, "how many, how much?"
Thank you all.
Very 73, Jim [email protected]
Some very good dialog has been taking place, lead by Juan Rivera as he heads up the prototype U Receiver build and test project.
Several very important questions have been raised but I'd like to address just one with this post.
I've volunteered to design and build the S2 Receiver and the C Transmitter and support microwave component efforts on the phased array for each. I am finishing efforts on a "prototype" single channel (assuming there might be several) S2 downconverter.
I fully recognize than "many" system design parameters have not yet been defined but I'm trying to get that "definition" effort moving along.
This is the first one I'd like to address.
In the coarse of designing the LO for the "prototype" S2 downconverter I have not been too concerned with use of the 10 MHz satellite clock. But I think it's time for "system" project guidelines to be developed for this issue since it can affect the design of all LO's. I have looked for guidance on the subject in Eaglepedia and have come up short. Point me in the right direction if it's there (and I just couldn't find it).
I hope I'm not rehashing old discussions (I've only been on the team since last October) but here are my questions:
1) What is the reason for requiring all LO's to be locked to a 10 MHz satellite system clock or are they?
2) Have the performance specifications for the 10 MHz clock been developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
My apologies for sending to the entire Eagle list but I'm not sure who has the responsibility for the clock.
Probably more questions to follow!!!
Regards...Bill - N6GHz
Bill et al: The requirement for the 10MHz reference descends from the July 2004 meeting in Orlando. As far as I know, it was never thoroughly justified, it was stated and made sense at the time. Still does, to me, tho I could be convinced on a case basis that we might not need it.
73, jim [email protected]
Bill Ress wrote:
Some very good dialog has been taking place, lead by Juan Rivera as he heads up the prototype U Receiver build and test project.
Several very important questions have been raised but I'd like to address just one with this post.
I've volunteered to design and build the S2 Receiver and the C Transmitter and support microwave component efforts on the phased array for each. I am finishing efforts on a "prototype" single channel (assuming there might be several) S2 downconverter.
I fully recognize than "many" system design parameters have not yet been defined but I'm trying to get that "definition" effort moving along.
This is the first one I'd like to address.
In the coarse of designing the LO for the "prototype" S2 downconverter I have not been too concerned with use of the 10 MHz satellite clock. But I think it's time for "system" project guidelines to be developed for this issue since it can affect the design of all LO's. I have looked for guidance on the subject in Eaglepedia and have come up short. Point me in the right direction if it's there (and I just couldn't find it).
I hope I'm not rehashing old discussions (I've only been on the team since last October) but here are my questions:
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
- Have the performance specifications for the 10 MHz clock been
developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
My apologies for sending to the entire Eagle list but I'm not sure who has the responsibility for the clock.
Probably more questions to follow!!!
Regards...Bill - N6GHz
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Bill Ress wrote:
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
That requirement comes from me. It is my fervent hope that we will be able to use the transponders for accurate coherent s/c ranging; therefore we want the TX and RX LOs to be related to a common (high stability) reference. There are also some (undocumented) desires (that may re$ult in $ome project $upport) to use the microwave transponders for high accuracy, intercontinental time & frequency synchronization.
- Have the performance specifications for the 10 MHz clock been
developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
My desire, if it can be promoted (from unnamed $ource$), to use what is often called an Ultra-Stable Oscillator (USO) of the type carried on a number of interplanetary s/c. I envision us being able to tweak the frequency slightly under ground command (i.e. a D/A converter built into the USO).
My apologies for sending to the entire Eagle list but I'm not sure who has the responsibility for the clock.
System level responsibilities are up for grabs AFAIK. So far, my contribution has been to say "It would tremendously augment capabilities if ...".
Please keep asking these questions! 73, Tom
Is the 10 MHz reference a possible single point of failure? Has it been made a requirement that all subsystems fail gracefully if the 10 MHz reference disappears?
Alan [email protected]
On Mon, 2007-04-09 at 20:06, Jim Sanford wrote:
Bill et al: The requirement for the 10MHz reference descends from the July 2004 meeting in Orlando. As far as I know, it was never thoroughly justified, it was stated and made sense at the time. Still does, to me, tho I could be convinced on a case basis that we might not need it.
73, jim [email protected]
Bill Ress wrote:
Some very good dialog has been taking place, lead by Juan Rivera as he heads up the prototype U Receiver build and test project.
Several very important questions have been raised but I'd like to address just one with this post.
I've volunteered to design and build the S2 Receiver and the C Transmitter and support microwave component efforts on the phased array for each. I am finishing efforts on a "prototype" single channel (assuming there might be several) S2 downconverter.
I fully recognize than "many" system design parameters have not yet been defined but I'm trying to get that "definition" effort moving along.
This is the first one I'd like to address.
In the coarse of designing the LO for the "prototype" S2 downconverter I have not been too concerned with use of the 10 MHz satellite clock. But I think it's time for "system" project guidelines to be developed for this issue since it can affect the design of all LO's. I have looked for guidance on the subject in Eaglepedia and have come up short. Point me in the right direction if it's there (and I just couldn't find it).
I hope I'm not rehashing old discussions (I've only been on the team since last October) but here are my questions:
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
- Have the performance specifications for the 10 MHz clock been
developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
My apologies for sending to the entire Eagle list but I'm not sure who has the responsibility for the clock.
Probably more questions to follow!!!
Regards...Bill - N6GHz
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Hello Bill!
My recollections of "oral history":
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
Earlier transponders often had frequency uncertainties of many kHz. For some applications (I seem to recall ranging early in the life of the spacecraft as we're trying to stabilize it and change its orbit) knowing the frequency is important. For general QSOs it is less so, especially with CAT interfaces to radios what can compensate for transponder errors as well as local offsets.
Also, the oscillators so referenced should be able to operate as well as past transponders in the absence of the 10 MHz reference.
Some of this desire may have been driven by the P5A requirements, which don't apply to Eagle. Doing 5 bps DBPSK signaling at S band requires some pretty amazing stability and phase noise characteristics, or so I'm told!
- Have the performance specifications for the 10 MHz clock been
developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
For Eagle, not to my knowledge.
73,
Lyle KK7P
Is the 10 MHz reference a possible single point of failure? Has it been made a requirement that all subsystems fail gracefully if the 10 MHz reference disappears?
The discussions always asserted that the oscillators must perform without the 10 MHz reference. If available, they should use it.
73,
Lyle KK7P
If you have tried to make contact through two independently varying systems such as a receiver with it's LO and a transmitter with it's LO. You would not need any additional justification. AO-40 was a very difficult satellite to use for that very reason. The U band receiver local oscillator had it's drifting characteristic and the S band Tx had its own LO. Between the two you never knew exactly what the transfer function would be. With a common reference oscillator hopefully closely controlled the transfer function will be much better known. With a common clock at least everything drifts together. With the higher frequencies of the C band system it will be even more important.
Lou McFadin W5DID [email protected]
On Apr 9, 2007, at 11:06 PM, Jim Sanford wrote:
Bill et al: The requirement for the 10MHz reference descends from the July 2004 meeting in Orlando. As far as I know, it was never thoroughly justified, it was stated and made sense at the time. Still does, to me, tho I could be convinced on a case basis that we might not need it.
73, jim [email protected]
Bill Ress wrote:
Some very good dialog has been taking place, lead by Juan Rivera as he heads up the prototype U Receiver build and test project.
Several very important questions have been raised but I'd like to address just one with this post.
I've volunteered to design and build the S2 Receiver and the C Transmitter and support microwave component efforts on the phased array for each. I am finishing efforts on a "prototype" single channel (assuming there might be several) S2 downconverter.
I fully recognize than "many" system design parameters have not yet been defined but I'm trying to get that "definition" effort moving along.
This is the first one I'd like to address.
In the coarse of designing the LO for the "prototype" S2 downconverter I have not been too concerned with use of the 10 MHz satellite clock. But I think it's time for "system" project guidelines to be developed for this issue since it can affect the design of all LO's. I have looked for guidance on the subject in Eaglepedia and have come up short. Point me in the right direction if it's there (and I just couldn't find it).
I hope I'm not rehashing old discussions (I've only been on the team since last October) but here are my questions:
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
- Have the performance specifications for the 10 MHz clock been
developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
My apologies for sending to the entire Eagle list but I'm not sure who has the responsibility for the clock.
Probably more questions to follow!!!
Regards...Bill - N6GHz
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Thanks Tom and to all who responded to my question regarding the 10 MHz satellite clock. Most helpful.
Tom, when you refer to "s/c ranging" are you referring to the S2 and C transponders?
From the comments received, it appears that the 10 MHz clock is another "system" issue that really needs defining early on and I will endeavor to do just that with the help of all who have inputs.
But before that can be done we need to know the certainly or uncertainty and the timing for the USO you referenced Tom. It sounds like a worthy goal if you can pull it off.
If indeed the clock is used by all LO's it is important that the LO designers know the reference's characteristics so that synthesis schemes and loop bandwidths can be better defined.
With that in mind, can you Tom, 1) determine what the specs of the $ystem USO might be (or point me to a place when I might deduce them), and 2) what's a realistic time frame for deciding if that $ugar daddy/mommy comes through with a commitment? We not only have to get a handle on the 10 MHz oscillator but the RF distribution circuitry after it.
In regards to the RF distribution circuitry, I count 8 users of the 10 Mhz clock. Help me out here if I missed one....
1) V Transmitter 2) U Receiver (maybe two?) 3) L Receivers (two) 4) S Transmitter 5) S2 Receiver 6) C Transmitter 7) IHU 8) Spare (for X or K beacon or a "contributing" customer)
Again comments are "graciously" appreciated...Bill - N6GHz
Tom Clark, K3IO wrote:
Bill Ress wrote:
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
That requirement comes from me. It is my fervent hope that we will be able to use the transponders for accurate coherent s/c ranging; therefore we want the TX and RX LOs to be related to a common (high stability) reference. There are also some (undocumented) desires (that may re$ult in $ome project $upport) to use the microwave transponders for high accuracy, intercontinental time & frequency synchronization.
- Have the performance specifications for the 10 MHz clock been
developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
My desire, if it can be promoted (from unnamed $ource$), to use what is often called an Ultra-Stable Oscillator (USO) of the type carried on a number of interplanetary s/c. I envision us being able to tweak the frequency slightly under ground command (i.e. a D/A converter built into the USO).
My apologies for sending to the entire Eagle list but I'm not sure who has the responsibility for the clock.
System level responsibilities are up for grabs AFAIK. So far, my contribution has been to say "It would tremendously augment capabilities if ...".
Please keep asking these questions! 73, Tom
Hello Bill!
In regards to the RF distribution circuitry, I count 8 users of the 10 MHz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
(9 and 10) - SDX processors
73,
Lyle KK7P
Since only UV supports the text mode with omnidirectional ground station antennas and this is the only linear transponder that operates over 75% of the orbit, I hope that we can fly two V transmitters and 2 U receivers. Each pair of receivers and transmitters could then connect to their gain and omni antennas via a transfer switch so that there is no single-point failure mode.
73,
John KD6OZH
----- Original Message ----- From: "Lyle Johnson" [email protected] To: "Bill Ress" [email protected] Cc: "EAGLE" [email protected]; [email protected] Sent: Tuesday, April 10, 2007 20:00 UTC Subject: [eagle] Re: Eagle 10 MHz Clock
Hello Bill!
In regards to the RF distribution circuitry, I count 8 users of the 10 MHz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
(9 and 10) - SDX processors
73,
Lyle KK7P
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
John,
Sounds like a good plan! But we probably need a "system" command decision - right?? Is this something project management can buy into, assuming we don't run into serious issues with space or weight?
Don't think power would be impacted since the spare unit would be in a power down mode.
John B. Stephensen wrote:
Since only UV supports the text mode with omnidirectional ground station antennas and this is the only linear transponder that operates over 75% of the orbit, I hope that we can fly two V transmitters and 2 U receivers. Each pair of receivers and transmitters could then connect to their gain and omni antennas via a transfer switch so that there is no single-point failure mode.
73,
John KD6OZH
----- Original Message ----- From: "Lyle Johnson" [email protected] To: "Bill Ress" [email protected] Cc: "EAGLE" [email protected]; [email protected] Sent: Tuesday, April 10, 2007 20:00 UTC Subject: [eagle] Re: Eagle 10 MHz Clock
Hello Bill!
In regards to the RF distribution circuitry, I count 8 users of the 10 MHz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
(9 and 10) - SDX processors
73,
Lyle KK7P
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
It shouldn't affect power consumption at all as the widget can power down spare units and the transfer relay can be latching. I don't know if it has been determined how many modules will fit in the hexagonal spaceframe, but there has to be more space than there was a year ago. This will be a high-level decision.
73,
John KD6OZH
----- Original Message ----- From: "Bill Ress" [email protected] To: "John B. Stephensen" [email protected] Cc: "Lyle Johnson" [email protected]; "EAGLE" [email protected]; [email protected] Sent: Tuesday, April 10, 2007 21:12 UTC Subject: Re: [eagle] Re: Eagle 10 MHz Clock
John,
Sounds like a good plan! But we probably need a "system" command decision - right?? Is this something project management can buy into, assuming we don't run into serious issues with space or weight?
Don't think power would be impacted since the spare unit would be in a power down mode.
John B. Stephensen wrote:
Since only UV supports the text mode with omnidirectional ground station antennas and this is the only linear transponder that operates over 75% of the orbit, I hope that we can fly two V transmitters and 2 U receivers. Each pair of receivers and transmitters could then connect to their gain and omni antennas via a transfer switch so that there is no single-point failure mode.
73,
John KD6OZH
----- Original Message ----- From: "Lyle Johnson" [email protected] To: "Bill Ress" [email protected] Cc: "EAGLE" [email protected]; [email protected] Sent: Tuesday, April 10, 2007 20:00 UTC Subject: [eagle] Re: Eagle 10 MHz Clock
Hello Bill!
In regards to the RF distribution circuitry, I count 8 users of the 10 MHz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
(9 and 10) - SDX processors
73,
Lyle KK7P
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Alan: This requirement came up in the peer review, and was imposed on the design.
It needs to become a system requirement. I've separately requested draft of such a list of requirements.
Thanks & 73, Jim
Alan Bloom wrote:
Is the 10 MHz reference a possible single point of failure? Has it been made a requirement that all subsystems fail gracefully if the 10 MHz reference disappears?
Alan [email protected]
On Mon, 2007-04-09 at 20:06, Jim Sanford wrote:
Bill et al: The requirement for the 10MHz reference descends from the July 2004 meeting in Orlando. As far as I know, it was never thoroughly justified, it was stated and made sense at the time. Still does, to me, tho I could be convinced on a case basis that we might not need it.
73, jim [email protected]
Bill Ress wrote:
Some very good dialog has been taking place, lead by Juan Rivera as he heads up the prototype U Receiver build and test project.
Several very important questions have been raised but I'd like to address just one with this post.
I've volunteered to design and build the S2 Receiver and the C Transmitter and support microwave component efforts on the phased array for each. I am finishing efforts on a "prototype" single channel (assuming there might be several) S2 downconverter.
I fully recognize than "many" system design parameters have not yet been defined but I'm trying to get that "definition" effort moving along.
This is the first one I'd like to address.
In the coarse of designing the LO for the "prototype" S2 downconverter I have not been too concerned with use of the 10 MHz satellite clock. But I think it's time for "system" project guidelines to be developed for this issue since it can affect the design of all LO's. I have looked for guidance on the subject in Eaglepedia and have come up short. Point me in the right direction if it's there (and I just couldn't find it).
I hope I'm not rehashing old discussions (I've only been on the team since last October) but here are my questions:
- What is the reason for requiring all LO's to be locked to a 10 MHz
satellite system clock or are they?
- Have the performance specifications for the 10 MHz clock been
developed and what are they (in particular phase noise, frequency stability, susceptibility to digital hash, and power level available to each using subsystem - to name a few)?
My apologies for sending to the entire Eagle list but I'm not sure who has the responsibility for the clock.
Probably more questions to follow!!!
Regards...Bill - N6GHz
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
All: Multiple receivers and transmitters/transfer switch remains an open item. There have been discussions, but no conclusions. Some who need to participate with me in that conversation have been unavailable for a while. We'll get there.
THanks & 73,' Jim
Bill Ress wrote:
John,
Sounds like a good plan! But we probably need a "system" command decision - right?? Is this something project management can buy into, assuming we don't run into serious issues with space or weight?
Don't think power would be impacted since the spare unit would be in a power down mode.
John B. Stephensen wrote:
Since only UV supports the text mode with omnidirectional ground station antennas and this is the only linear transponder that operates over 75% of the orbit, I hope that we can fly two V transmitters and 2 U receivers. Each pair of receivers and transmitters could then connect to their gain and omni antennas via a transfer switch so that there is no single-point failure mode.
73,
John KD6OZH
----- Original Message ----- From: "Lyle Johnson" [email protected] To: "Bill Ress" [email protected] Cc: "EAGLE" [email protected]; [email protected] Sent: Tuesday, April 10, 2007 20:00 UTC Subject: [eagle] Re: Eagle 10 MHz Clock
Hello Bill!
In regards to the RF distribution circuitry, I count 8 users of the 10 MHz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
(9 and 10) - SDX processors
73,
Lyle KK7P
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Bill Ress wrote:
(snip)
If indeed the clock is used by all LO's it is important that the LO designers know the reference's characteristics so that synthesis schemes and loop bandwidths can be better defined.
Assume that it is a low noise crystal. Signals will come from an N-port driver that is a part of the USO. A good standard level will be 0 dBm into 50 ohms (although it could be a tad higher -- like up to 1V RMS = +13 dBm if really needed).
I would suggest that each user system could use the precision reference if it is available, but should switch over to an internal oscillator if the precision source goes away. This is the way most counters, spectrum analyzers, etc work and it permits a good, simple "fail soft" option.
With that in mind, can you Tom, 1) determine what the specs of the $ystem USO might be (or point me to a place when I might deduce them), and 2) what's a realistic time frame for deciding if that $ugar daddy/mommy comes through with a commitment? We not only have to get a handle on the 10 MHz oscillator but the RF distribution circuitry after it.
In regards to the RF distribution circuitry, I count 8 users of the 10 Mhz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
As Lyle mentioned, all the DSP widgets need the reference signal also. For precise ranging it is likely that some really tight special DSP code will be loaded into the DSP engines for maximum accuracy. This will be to ensure the flattest possible phase response thru the system (the group delay tau is measured as d(phase)/d(freq) over the however wide the passband can be).
Thinking of obtaining the best possible accuracy, we may want to do U/V and a microwave pair simultaneously to provide a calibration of the ionosphere; the one-way group delay thru the ionosphere varies as 1/f² and has a magnitude ~2M at S-band.
73, Tom
On Tue, 2007-04-10 at 14:12 -0700, Bill Ress wrote:
Don't think power would be impacted since the spare unit would be in a power down mode.
Please don't assume that it's ok to have the power to a command receiver switchable without substantial discussion and review. All prior AMSAT projects that I'm aware of have had command receivers always on, even if they weren't always in use. I'm pretty confident that includes both of a redundant pair. Happy to be corrected by others with better knowledge of history if I'm mis-remembering some relevant case.
Bdale
In my recollection there has been no option to anything with a command receiver at all in past satellites. This receiver was ON to be able to do its function regardless of other 'activities' on the satellite. In other words, it could not be messed with for any reason. Such a capability is absolutely essential for the health (and recovery) of the satellite and its mission.
Dick Jansson, KD1K [email protected] [email protected] ---------------------------
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bdale Garbee Sent: Wednesday, 11 April, 2007 1439 To: Bill Ress Cc: [email protected]; EAGLE Subject: [eagle] Re: Eagle 10 MHz Clock
On Tue, 2007-04-10 at 14:12 -0700, Bill Ress wrote:
Don't think power would be impacted since the spare unit would be in a power down mode.
Please don't assume that it's ok to have the power to a command receiver switchable without substantial discussion and review. All prior AMSAT projects that I'm aware of have had command receivers always on, even if they weren't always in use. I'm pretty confident that includes both of a redundant pair. Happy to be corrected by others with better knowledge of history if I'm mis-remembering some relevant case.
Bdale
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Hi Dick and Bdale,
Good points about keeping the command receiver on 100% - no issue there. But I think the matter is somewhat confused (at least for me) since I believe the command receiver that John has designed is also the data/analog receiver. I don't recall that being the case is the past satellites. If command and data function stay combined, then that's all the more reason for considering John's suggestion for two U receivers.
Correct me if I'm wrong, but I also understand that there will also be a separate L command receiver, but again not sure about that too.
Gosh - just think how handy a satellite top level block diagram might be, even if its a work in progress. Or is there one and I haven't bumped into it.
Regards...Bill - N6GHz
Dick Jansson-rr wrote:
In my recollection there has been no option to anything with a command receiver at all in past satellites. This receiver was ON to be able to do its function regardless of other 'activities' on the satellite. In other words, it could not be messed with for any reason. Such a capability is absolutely essential for the health (and recovery) of the satellite and its mission.
Dick Jansson, KD1K [email protected] [email protected]
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bdale Garbee Sent: Wednesday, 11 April, 2007 1439 To: Bill Ress Cc: [email protected]; EAGLE Subject: [eagle] Re: Eagle 10 MHz Clock
On Tue, 2007-04-10 at 14:12 -0700, Bill Ress wrote:
Don't think power would be impacted since the spare unit would be in a power down mode.
Please don't assume that it's ok to have the power to a command receiver switchable without substantial discussion and review. All prior AMSAT projects that I'm aware of have had command receivers always on, even if they weren't always in use. I'm pretty confident that includes both of a redundant pair. Happy to be corrected by others with better knowledge of history if I'm mis-remembering some relevant case.
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Hello Bill!
Good points about keeping the command receiver on 100% - no issue there. But I think the matter is somewhat confused (at least for me) since I believe the command receiver that John has designed is also the data/analog receiver. I don't recall that being the case is the past satellites. If command and data function stay combined, then that's all the more reason for considering John's suggestion.
In the past, the "command receiver" used the same front end as the transponder receiver. The difference was an IF tap that was then downconverted to baseband to drive a hardware command decoder.
Thus, all uplink that had command capability had receivers that were always on.
One rule learned the hard way is you *never* turn off a command receiver. It's also why command receivers, at least, were never frequency agile. It's bad enough to recover a spacecraft if you are commanding it in the blind - it's even hardware if you have no idea where the receiver might be tuned. So, we always used crystal oscillator/multipliers, or PLLS with pins-selection of dividers. Using a serial-load PLL adds a lot of risk -- not sure what the reward is for the risk.
Not to say we need to always do what worked in the past, just that we should have compelling reasons to change things that relate to spacecraft safety and health.
73,
Lyle KK7P
Hi Tom,
Thanks for your inputs.
Do you have a time frame for your USO benefactor's commitment to the program??
We're designing based on 10 MHz reference assumptions and that leaves me, at least, with an empty feeling. Since over 10 subsystems will use this reference, it would be great to get this block defined.
As you know John has already designed for operating without the 10 MHz satellite clock and I'm also doing the same.
Oh - - - help with out Tom. You used "s/c ranging" in you one of your recent posts. The "s/c" stands for what??? S and C transponders??
Regards...Bill - N6GHz
Tom Clark, K3IO wrote:
Bill Ress wrote:
(snip)
If indeed the clock is used by all LO's it is important that the LO designers know the reference's characteristics so that synthesis schemes and loop bandwidths can be better defined.
Assume that it is a low noise crystal. Signals will come from an N-port driver that is a part of the USO. A good standard level will be 0 dBm into 50 ohms (although it could be a tad higher -- like up to 1V RMS = +13 dBm if really needed).
I would suggest that each user system could use the precision reference if it is available, but should switch over to an internal oscillator if the precision source goes away. This is the way most counters, spectrum analyzers, etc work and it permits a good, simple "fail soft" option.
With that in mind, can you Tom, 1) determine what the specs of the $ystem USO might be (or point me to a place when I might deduce them), and 2) what's a realistic time frame for deciding if that $ugar daddy/mommy comes through with a commitment? We not only have to get a handle on the 10 MHz oscillator but the RF distribution circuitry after it.
In regards to the RF distribution circuitry, I count 8 users of the 10 Mhz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
As Lyle mentioned, all the DSP widgets need the reference signal also. For precise ranging it is likely that some really tight special DSP code will be loaded into the DSP engines for maximum accuracy. This will be to ensure the flattest possible phase response thru the system (the group delay tau is measured as d(phase)/d(freq) over the however wide the passband can be).
Thinking of obtaining the best possible accuracy, we may want to do U/V and a microwave pair simultaneously to provide a calibration of the ionosphere; the one-way group delay thru the ionosphere varies as 1/f² and has a magnitude ~2M at S-band.
73, Tom
Bill,
s/c means SpaceCraft.
It is a waste of time to design for operation without the 10 MHz satellite oscillator (it is not a clock). The design will simply need to be redone. On the other hand, if designs incorporate their own soft fail options, so much the better.
I expect a design for the 10MHz satellite reference based on a design Tom and I have seen that includes its own soft fail redundancy. I will discuss this possibility with Tom soon.
Rick W2GPS AMSAT LM2232
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bill Ress Sent: Wednesday, April 11, 2007 1:17 PM To: [email protected] Cc: EAGLE Subject: [eagle] Re: Eagle 10 MHz Clock
Hi Tom,
Thanks for your inputs.
Do you have a time frame for your USO benefactor's commitment to the program??
We're designing based on 10 MHz reference assumptions and that leaves me, at least, with an empty feeling. Since over 10 subsystems will use this reference, it would be great to get this block defined.
As you know John has already designed for operating without the 10 MHz satellite clock and I'm also doing the same.
Oh - - - help with out Tom. You used "s/c ranging" in you one of your recent posts. The "s/c" stands for what??? S and C transponders??
Regards...Bill - N6GHz
Tom Clark, K3IO wrote:
Bill Ress wrote:
(snip)
If indeed the clock is used by all LO's it is important that the LO designers know the reference's characteristics so that synthesis schemes and loop bandwidths can be better defined.
Assume that it is a low noise crystal. Signals will come from an N-port driver that is a part of the USO. A good standard level will be 0 dBm into 50 ohms (although it could be a tad higher -- like up to 1V RMS = +13 dBm if really needed).
I would suggest that each user system could use the precision reference if it is available, but should switch over to an internal oscillator if the precision source goes away. This is the way most counters, spectrum analyzers, etc work and it permits a good, simple "fail soft" option.
With that in mind, can you Tom, 1) determine what the specs of the $ystem USO might be (or point me to a place when I might deduce them), and 2) what's a realistic time frame for deciding if that $ugar daddy/mommy comes through with a commitment? We not only have to get a handle on the 10 MHz oscillator but the RF distribution circuitry after
it.
In regards to the RF distribution circuitry, I count 8 users of the 10 Mhz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
As Lyle mentioned, all the DSP widgets need the reference signal also. For precise ranging it is likely that some really tight special DSP code will be loaded into the DSP engines for maximum accuracy. This will be to ensure the flattest possible phase response thru the system (the group delay tau is measured as d(phase)/d(freq) over the however wide the passband can be).
Thinking of obtaining the best possible accuracy, we may want to do U/V and a microwave pair simultaneously to provide a calibration of the ionosphere; the one-way group delay thru the ionosphere varies as 1/f² and has a magnitude ~2M at S-band.
73, Tom
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Thanks for the clarification on the past command receivers.
I agree with you fully about the frequency agility issue. If it's not needed for a mission function, then it could be more of headache than a feature. But then some of the receivers on AO-51 are agile and I'm not aware of any issues.
On the S2 Receiver - the LO is "not" agile and likewise for the C Transmitter LO. The prototype is using a synthesizer chip (Peregrine PE3341) but it's EEPROM programmed before installing onto the PCB. Yes - I know about the EEPROM radiation issue but I have a fall back position with the "hardwired" version if it becomes a real problem.
Lyle Johnson wrote:
Hello Bill!
Good points about keeping the command receiver on 100% - no issue there. But I think the matter is somewhat confused (at least for me) since I believe the command receiver that John has designed is also the data/analog receiver. I don't recall that being the case is the past satellites. If command and data function stay combined, then that's all the more reason for considering John's suggestion.
In the past, the "command receiver" used the same front end as the transponder receiver. The difference was an IF tap that was then downconverted to baseband to drive a hardware command decoder.
Thus, all uplink that had command capability had receivers that were always on.
One rule learned the hard way is you *never* turn off a command receiver. It's also why command receivers, at least, were never frequency agile. It's bad enough to recover a spacecraft if you are commanding it in the blind - it's even hardware if you have no idea where the receiver might be tuned. So, we always used crystal oscillator/multipliers, or PLLS with pins-selection of dividers. Using a serial-load PLL adds a lot of risk -- not sure what the reward is for the risk.
Not to say we need to always do what worked in the past, just that we should have compelling reasons to change things that relate to spacecraft safety and health.
73,
Lyle KK7P
Rick,
Thanks for the clarification. I thought Tom was referring to the using the "S/C" transponders for ranging - well I guess he would be using them.
My post below says "As you know John has already designed for operating without the 10 MHz satellite clock and I'm also doing the same." so I'm on the same page with you.
Regards...Bill - N6GHz
Rick Hambly (W2GPS) wrote:
Bill,
s/c means SpaceCraft.
It is a waste of time to design for operation without the 10 MHz satellite oscillator (it is not a clock). The design will simply need to be redone. On the other hand, if designs incorporate their own soft fail options, so much the better.
I expect a design for the 10MHz satellite reference based on a design Tom and I have seen that includes its own soft fail redundancy. I will discuss this possibility with Tom soon.
Rick W2GPS AMSAT LM2232
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bill Ress Sent: Wednesday, April 11, 2007 1:17 PM To: [email protected] Cc: EAGLE Subject: [eagle] Re: Eagle 10 MHz Clock
Hi Tom,
Thanks for your inputs.
Do you have a time frame for your USO benefactor's commitment to the program??
We're designing based on 10 MHz reference assumptions and that leaves me, at least, with an empty feeling. Since over 10 subsystems will use this reference, it would be great to get this block defined.
As you know John has already designed for operating without the 10 MHz satellite clock and I'm also doing the same.
Oh - - - help with out Tom. You used "s/c ranging" in you one of your recent posts. The "s/c" stands for what??? S and C transponders??
Regards...Bill - N6GHz
Tom Clark, K3IO wrote:
Bill Ress wrote:
(snip)
If indeed the clock is used by all LO's it is important that the LO designers know the reference's characteristics so that synthesis schemes and loop bandwidths can be better defined.
Assume that it is a low noise crystal. Signals will come from an N-port driver that is a part of the USO. A good standard level will be 0 dBm into 50 ohms (although it could be a tad higher -- like up to 1V RMS = +13 dBm if really needed).
I would suggest that each user system could use the precision reference if it is available, but should switch over to an internal oscillator if the precision source goes away. This is the way most counters, spectrum analyzers, etc work and it permits a good, simple "fail soft" option.
With that in mind, can you Tom, 1) determine what the specs of the $ystem USO might be (or point me to a place when I might deduce them), and 2) what's a realistic time frame for deciding if that $ugar daddy/mommy comes through with a commitment? We not only have to get a handle on the 10 MHz oscillator but the RF distribution circuitry after
it.
In regards to the RF distribution circuitry, I count 8 users of the 10 Mhz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
As Lyle mentioned, all the DSP widgets need the reference signal also. For precise ranging it is likely that some really tight special DSP code will be loaded into the DSP engines for maximum accuracy. This will be to ensure the flattest possible phase response thru the system (the group delay tau is measured as d(phase)/d(freq) over the however wide the passband can be).
Thinking of obtaining the best possible accuracy, we may want to do U/V and a microwave pair simultaneously to provide a calibration of the ionosphere; the one-way group delay thru the ionosphere varies as 1/f² and has a magnitude ~2M at S-band.
73, Tom
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Hello Bill!
I agree with you fully about the frequency agility issue. If it's not needed for a mission function, then it could be more of headache than a feature. But then some of the receivers on AO-51 are agile and I'm not aware of any issues.
AO-51 has 4 crystal-controlled (i.e., not using PLL synthesizer in the L.O.) receivers, and one frequency-agile receiver. The frequency agile receiver was a mission requirement.
All of the receivers can be used for command operation, but the frequency agile one is so wired because it was "free" - no mass or complexity penalty. That is because the flight computer has 6 demodulators built in, and a total of five receivers on the spacecraft. It is not intended for use in an emergency recovery scenario.
73,
Lyle KK7P
It was my understanding that we were going to use Mirek's L band receiver for the command receiver. It has an excellent track record and is available.
Lou McFadin W5DID [email protected]
On Apr 11, 2007, at 2:04 PM, Lyle Johnson wrote:
Hello Bill!
I agree with you fully about the frequency agility issue. If it's not needed for a mission function, then it could be more of headache than a feature. But then some of the receivers on AO-51 are agile and I'm not aware of any issues.
AO-51 has 4 crystal-controlled (i.e., not using PLL synthesizer in the L.O.) receivers, and one frequency-agile receiver. The frequency agile receiver was a mission requirement.
All of the receivers can be used for command operation, but the frequency agile one is so wired because it was "free" - no mass or complexity penalty. That is because the flight computer has 6 demodulators built in, and a total of five receivers on the spacecraft. It is not intended for use in an emergency recovery scenario.
73,
Lyle KK7P
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Hello Lou!
It was my understanding that we were going to use Mirek's L band receiver for the command receiver. It has an excellent track record and is available.
No problem. I was referring to the comment about AO-51. I didn't mean to muddy the waters.
73,
Lyle KK7P
Lou McFadin W5DID [email protected]
On Apr 11, 2007, at 2:04 PM, Lyle Johnson wrote:
Hello Bill!
I agree with you fully about the frequency agility issue. If it's not needed for a mission function, then it could be more of headache than a feature. But then some of the receivers on AO-51 are agile and I'm not aware of any issues.
AO-51 has 4 crystal-controlled (i.e., not using PLL synthesizer in the L.O.) receivers, and one frequency-agile receiver. The frequency agile receiver was a mission requirement.
All of the receivers can be used for command operation, but the frequency agile one is so wired because it was "free" - no mass or complexity penalty. That is because the flight computer has 6 demodulators built in, and a total of five receivers on the spacecraft. It is not intended for use in an emergency recovery scenario.
73,
Lyle KK7P
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
The U-band receiver is different from previous receivers due to the requirement that it stay linear while receving PAVE PAWS radar pulses. It probably consumes 10 times more power than previous receivers so if there are to be two of them, one will probably have to be switched off. The L-band receiver can be low power so it can be on all the time.
73,
John KD6OZH
The PLL frequency can be hardwired, but not all register bits are brought out to the package pins. We would have to live with a selection of frequencies in increments of 500 kHz.
73,
John KD6OZH
All:
It is certainly my understanding as a requirement and my intent that receivers which can be used for command (U, L) will always have power. 73, Jim [email protected]
Bdale Garbee wrote:
On Tue, 2007-04-10 at 14:12 -0700, Bill Ress wrote:
Don't think power would be impacted since the spare unit would be in a power down mode.
Please don't assume that it's ok to have the power to a command receiver switchable without substantial discussion and review. All prior AMSAT projects that I'm aware of have had command receivers always on, even if they weren't always in use. I'm pretty confident that includes both of a redundant pair. Happy to be corrected by others with better knowledge of history if I'm mis-remembering some relevant case.
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
All: U and L receivers will always be on, is my understanding of requirements. I've seen nothing to change that. The subject of 1 or 2 receivers at U and/or L is fuzzy, and a topic I wish to bring to closure over the next month or so.
There is a top-level block diagram, possibly in need of slight revision, on EaglePedia, in the report of the "Black Forest" meeting in Oct/Nov of 2005.
Tom: Pls forward to Bill.
Thanks & 73, Jim [email protected]
Bill Ress wrote:
Hi Dick and Bdale,
Good points about keeping the command receiver on 100% - no issue there. But I think the matter is somewhat confused (at least for me) since I believe the command receiver that John has designed is also the data/analog receiver. I don't recall that being the case is the past satellites. If command and data function stay combined, then that's all the more reason for considering John's suggestion for two U receivers.
Correct me if I'm wrong, but I also understand that there will also be a separate L command receiver, but again not sure about that too.
Gosh - just think how handy a satellite top level block diagram might be, even if its a work in progress. Or is there one and I haven't bumped into it.
Regards...Bill - N6GHz
Dick Jansson-rr wrote:
In my recollection there has been no option to anything with a command receiver at all in past satellites. This receiver was ON to be able to do its function regardless of other 'activities' on the satellite. In other words, it could not be messed with for any reason. Such a capability is absolutely essential for the health (and recovery) of the satellite and its mission.
Dick Jansson, KD1K [email protected] [email protected]
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bdale Garbee Sent: Wednesday, 11 April, 2007 1439 To: Bill Ress Cc: [email protected]; EAGLE Subject: [eagle] Re: Eagle 10 MHz Clock
On Tue, 2007-04-10 at 14:12 -0700, Bill Ress wrote:
Don't think power would be impacted since the spare unit would be in a power down mode.
Please don't assume that it's ok to have the power to a command receiver switchable without substantial discussion and review. All prior AMSAT projects that I'm aware of have had command receivers always on, even if they weren't always in use. I'm pretty confident that includes both of a redundant pair. Happy to be corrected by others with better knowledge of history if I'm mis-remembering some relevant case.
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
All: All systems should be designed to fail gracefully upon loss of the 10MHz reference. This was a key discussion in the UHF peer review. This will be clarified when I get a chance to update the FRD, which is low priority right now, compared to getting test results on U RX. 73, Jim [email protected]
Rick Hambly (W2GPS) wrote:
Bill,
s/c means SpaceCraft.
It is a waste of time to design for operation without the 10 MHz satellite oscillator (it is not a clock). The design will simply need to be redone. On the other hand, if designs incorporate their own soft fail options, so much the better.
I expect a design for the 10MHz satellite reference based on a design Tom and I have seen that includes its own soft fail redundancy. I will discuss this possibility with Tom soon.
Rick W2GPS AMSAT LM2232
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Bill Ress Sent: Wednesday, April 11, 2007 1:17 PM To: [email protected] Cc: EAGLE Subject: [eagle] Re: Eagle 10 MHz Clock
Hi Tom,
Thanks for your inputs.
Do you have a time frame for your USO benefactor's commitment to the program??
We're designing based on 10 MHz reference assumptions and that leaves me, at least, with an empty feeling. Since over 10 subsystems will use this reference, it would be great to get this block defined.
As you know John has already designed for operating without the 10 MHz satellite clock and I'm also doing the same.
Oh - - - help with out Tom. You used "s/c ranging" in you one of your recent posts. The "s/c" stands for what??? S and C transponders??
Regards...Bill - N6GHz
Tom Clark, K3IO wrote:
Bill Ress wrote:
(snip)
If indeed the clock is used by all LO's it is important that the LO designers know the reference's characteristics so that synthesis schemes and loop bandwidths can be better defined.
Assume that it is a low noise crystal. Signals will come from an N-port driver that is a part of the USO. A good standard level will be 0 dBm into 50 ohms (although it could be a tad higher -- like up to 1V RMS = +13 dBm if really needed).
I would suggest that each user system could use the precision reference if it is available, but should switch over to an internal oscillator if the precision source goes away. This is the way most counters, spectrum analyzers, etc work and it permits a good, simple "fail soft" option.
With that in mind, can you Tom, 1) determine what the specs of the $ystem USO might be (or point me to a place when I might deduce them), and 2) what's a realistic time frame for deciding if that $ugar daddy/mommy comes through with a commitment? We not only have to get a handle on the 10 MHz oscillator but the RF distribution circuitry after
it.
In regards to the RF distribution circuitry, I count 8 users of the 10 Mhz clock. Help me out here if I missed one....
- V Transmitter
- U Receiver (maybe two?)
- L Receivers (two)
- S Transmitter
- S2 Receiver
- C Transmitter
- IHU
- Spare (for X or K beacon or a "contributing" customer)
As Lyle mentioned, all the DSP widgets need the reference signal also. For precise ranging it is likely that some really tight special DSP code will be loaded into the DSP engines for maximum accuracy. This will be to ensure the flattest possible phase response thru the system (the group delay tau is measured as d(phase)/d(freq) over the however wide the passband can be).
Thinking of obtaining the best possible accuracy, we may want to do U/V and a microwave pair simultaneously to provide a calibration of the ionosphere; the one-way group delay thru the ionosphere varies as 1/f² and has a magnitude ~2M at S-band.
73, Tom
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
And my first fiat for 2007 follows:
That will not change.
Bob N4HY
Bdale Garbee wrote:
On Tue, 2007-04-10 at 14:12 -0700, Bill Ress wrote:
Don't think power would be impacted since the spare unit would be in a power down mode.
Please don't assume that it's ok to have the power to a command receiver switchable without substantial discussion and review. All prior AMSAT projects that I'm aware of have had command receivers always on, even if they weren't always in use. I'm pretty confident that includes both of a redundant pair. Happy to be corrected by others with better knowledge of history if I'm mis-remembering some relevant case.
Bdale
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Louis McFadin wrote:
It was my understanding that we were going to use Mirek's L band receiver for the command receiver. It has an excellent track record and is available.
That is correct.
Lou McFadin
W5DID
Bob N4HY
participants (11)
-
Alan Bloom -
Bdale Garbee -
Bill Ress -
Dick Jansson-rr -
Jim Sanford -
John B. Stephensen -
Louis McFadin -
Lyle Johnson -
Rick Hambly (W2GPS) -
Robert McGwier -
Tom Clark, K3IO