Recent arguments and proposals, I am off to Tuscon
I spent yesterday in a lawyer's office in Washington D.C. for AMSAT and actually enjoyed myself. I followed that with a mad dash back to Trenton to teach the SDR class Frank and I are teaching. Microchip is assisting us beautifully and we have a class full of eager students wanting to take on Suitsat-II and Eagle pieces for their design projects. I apologize for this week being so busy for me that I am unable to jump on to much of the discussions this week on BB and here in Eagle.
Let me dash off some quick comments.
I do not believe we can successfully build the X band component to the modified DCP system. I believe we will be killed by all sorts of LO problems including, but not limited, to phase noise issues. I am already a week behind in delivering Stephensen an analysis of the phase noise on the Class 1 users in SDX, I will add to this a system analysis of the required oscillator performance to use X band in the DCP. Remember, this is a weak signal mode and we are attempting to operate with only a few dB of margin at best. We cannot shed 1 or 2 more in implementation loss (if we are lucky).
I support John's contention that we should choose a band that is currently available world wide for the uplink on which we can feasibly build a system. Pick L or S1 is my recommendation. We chose S1 for all of these reasons.
If you choose L, we can put in two L's or share one with SDX. The antenna is the same required area, but the packing of the antenna on the spacecraft becomes more problematic. I understand Rick's motivation to not get hammered at the annual meeting. Welcome to the presidency. It is not a reason to make a bad choice for the uplink which will kill the utility of the package is my current opinion.
My current vote: stay with what was decided in San Diego or risk L as the primary uplink. I believe that a serious analysis of the impact of trying to get the dual band L/C antenna packed together will be a very illuminating exercise and I believe we will inevitably be led back to the SD decision based on system analysis rather than emotional analysis.
Bob
All,
I would like to reiterate my proposal for the Eagle band plan.
a) Keep the U/V SDX transponder as is.
b) Move C-C Rider's primary uplink to the S2-band (3400-3410 MHz). Also provide a backup uplink on L-band (1260-1270 MHz) but with fixed antennas optimized for use at apogee.
c) Implement an L/S SDX transponder, essentially identical to the U/S SDX transponder. This transponder would use fixed antennas and so will be usable near apogee. It would serve as a backup command and control access to the IHU. By being separate it would reduce the risk of common component failures. This would not use a TSFR module. This restores a promise we made to our membership that they have reasonably come to expect from Eagle.
In a message this morning N4HY said "I support John's contention that we should choose a band that is currently available world wide for the uplink on which we can feasibly build a system. Pick L or S1 is my recommendation. We chose S1 for all of these reasons." This is precisely the kind of political thinking that got us into the mess we are in now. The technical group should have stuck with the best technical result they identified in SDO for C-C Rider, an S2 uplink to replace the C uplink, and leave the political ramifications to be evaluated separately. It was clear in the SDO meeting that S2 is the best technical solution. A secondary access through L-band should mitigate the short term political fallout and this plan provides incentive to solve the political issues that otherwise will languish until S2 is gone.
Rick W2GPS AMSAT LM2232
Since I'm proposing X-band as a downlink, the main issue is LO phase noise requrements for C-band uplinks.
The downlink operates at 20 times the bit and baud rate of the uplinks, so I don't think that we will encounter LO phase noise problems there. The most critical LO will be that for the C receiver. However, PSK31 (31.25 Baud) is being used successfully at 30 MHz and the class 2 uplinks (4800 bps) will operate at 9600 Baud or more. This indicates that operation is possible at 30 MHz * 9600/31.25 or 9.216 GHz for class 2 users. Actually, operation is possible at much higher frequencies as the LOs in many HF radios are quite noisy and we can design low phase noise LOs.
Doppler shift is another issue, but 1200 Baud links are used routinely at 435 MHz in LEO satellites and a HEO will have 10 times less Doppler. This implies that operation is possible at 435MHz * 10 * 9600/1200 or 34.8 GHz.
Another way to look at the problem is that we are planning on 30-50 bps class 1 users on 435 MHz. If we can do that, then we can support 4800 bps class 2 users at 435 MHz * 4800/50 or 41.76 GHz. We were originally planning on having class 1 users using a C-band uplink and class 2 will be much easier.
I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity of the satellite.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "'EAGLE'" [email protected] Sent: Thursday, September 14, 2006 09:19 UTC Subject: [eagle] Recent arguments and proposals, I am off to Tuscon
I spent yesterday in a lawyer's office in Washington D.C. for AMSAT and actually enjoyed myself. I followed that with a mad dash back to Trenton to teach the SDR class Frank and I are teaching. Microchip is assisting us beautifully and we have a class full of eager students wanting to take on Suitsat-II and Eagle pieces for their design projects. I apologize for this week being so busy for me that I am unable to jump on to much of the discussions this week on BB and here in Eagle.
Let me dash off some quick comments.
I do not believe we can successfully build the X band component to the modified DCP system. I believe we will be killed by all sorts of LO problems including, but not limited, to phase noise issues. I am already a week behind in delivering Stephensen an analysis of the phase noise on the Class 1 users in SDX, I will add to this a system analysis of the required oscillator performance to use X band in the DCP. Remember, this is a weak signal mode and we are attempting to operate with only a few dB of margin at best. We cannot shed 1 or 2 more in implementation loss (if we are lucky).
I support John's contention that we should choose a band that is currently available world wide for the uplink on which we can feasibly build a system. Pick L or S1 is my recommendation. We chose S1 for all of these reasons.
If you choose L, we can put in two L's or share one with SDX. The antenna is the same required area, but the packing of the antenna on the spacecraft becomes more problematic. I understand Rick's motivation to not get hammered at the annual meeting. Welcome to the presidency. It is not a reason to make a bad choice for the uplink which will kill the utility of the package is my current opinion.
My current vote: stay with what was decided in San Diego or risk L as the primary uplink. I believe that a serious analysis of the impact of trying to get the dual band L/C antenna packed together will be a very illuminating exercise and I believe we will inevitably be led back to the SD decision based on system analysis rather than emotional analysis.
Bob
-- 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 [email protected] http://amsat.org/mailman/listinfo/eagle
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
I'm guessing that a worldwide ITU allocation results more availability than when one region is excluded. I beleive that Bob has asked for hard information on non-availability of S1 in countries outside the U.S. Perhaps the question should cover the entire microwave spectrum.
73,
John KD6OZH
----- Original Message ----- From: "Lee McLamb" [email protected] To: "'EAGLE'" [email protected] Sent: Friday, September 15, 2006 22:59 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
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
Outside of finding hard proof that S1 is unavailable in LU, I have not found another example and no one has emailed me their input saying anything to the contrary. I believe that we are going to have to do this study ourselves.
L is not a solution for the primary uplink for the DCP because of the CC&R antenna. I do not believe we can feed a conventional 60cm dish with a dual band feed that includes L. The aperture efficiency on C would drop too low to use even if we could get the L band feed to be usable. L and 2 foot dish aren't really compatible. I don't think even an offset feed will help. I will ask Tom and others to comment on the feasibility of this. I let this slip right past me when I was thinking about the alternatives. L would seem to require two separate antennas and I am loathe to go there.
It is irrelevant where the phase noise arises, on the spacecraft or on the ground. The convolution of all of the sources from the spacecraft transmitter through the receiver LO's and samplers on the ground will lead to a system cumulative noise rise due to oscillator phase noise irrespective of where the contribution arises. We might be able to overcome this on the spacecraft with more transmit power but then we have to figure out what to do with the extra heat . The heat was already going to be larger for X if we assumed perfect phase noise LO because of the lower efficiency of those devices. We still need a certain EIRP to close the link and lower efficiency does not lower the requirement to emit a certain EIRP. Since there is a fixed power budget given the proposed size, we would have to take power from the linear transponder, etc. we seem to be working to protect. The greatly increased pointing requirements on the spacecraft and ground (with 4 times as many elements on power amplifiers needed on the spacecraft for the phased array) given our constant aperture solution, coupled with lower efficiency leading to increased DC power consumption on the spacecraft, and with the inevitably higher phase noise all seem to mitigate against attempting X. I would need to see a design with some numbers but let's just say that for now I dismiss this proposal until somebody proves my entire thinking to be way off base.
We are left with S1 and S2 as the possible uplinks for the DCP that preserves the CC&R, first responder communications system. It is the contention of Emily that U/V is a crap choice for the linear transponder. Yet P3E is including it as its primary transponder. But if we accept ther premise that we don't want to put this on U/V then that argues for L/S1 for the SDX and S2/C for the DCP and we give up on region 1 accessing our digital communications experiment and our first all microwave satellite.
All of these suggestions coming fast and furious need to slow and before finger hits the key, some consideration for how the suggestion impacts the entire system need to be undertaken as requirement 1 in your personal analysis before the suggestion hits the street.
Bob
I put in a tentative bid for almost $250,000 in the upcoming budget for engineering for the coming year but no one is going to allow to me say I need about a quarter mill, trust me. If I call Jim and he does not have your team's budget numbers (as in I have not submitted numbers either), then I am going to call you to get them (I just gave myself a call). I am going to get some kind of SWAG at a number that includes hardware, travel, tools, and telecommunications. We are putting together a unified engineering budget that includes Eagle, P3E, Suitsat II, etc. so these numbers are needed.
On our system recommendation, I am going to get a decision on the overall plan before the board meeting as to the final form of our recommendation so Jim can present that to board. If this decision must be made by one or two people, so be it. We are going to decide on the system by then. PERIOD. If you have a dog in this fight, give that cur a kick in the rear.
John B. Stephensen wrote:
I'm guessing that a worldwide ITU allocation results more availability than when one region is excluded. I beleive that Bob has asked for hard information on non-availability of S1 in countries outside the U.S. Perhaps the question should cover the entire microwave spectrum.
73,
John KD6OZH
----- Original Message ----- From: "Lee McLamb" [email protected] To: "'EAGLE'" [email protected] Sent: Friday, September 15, 2006 22:59 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
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
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
Has Agrentina banned transmission on S1 for all amateur services -- terrestrial, earth and space stations?
Are we all still agreed that the primary analog and digital transponders must provide access over 75% of the orbit for ground stations using the minimum antenna/uplink power configuration?
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "'EAGLE'" [email protected] Sent: Saturday, September 16, 2006 13:10 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Outside of finding hard proof that S1 is unavailable in LU, I have not found another example and no one has emailed me their input saying anything to the contrary. I believe that we are going to have to do this study ourselves.
L is not a solution for the primary uplink for the DCP because of the CC&R antenna. I do not believe we can feed a conventional 60cm dish with a dual band feed that includes L. The aperture efficiency on C would drop too low to use even if we could get the L band feed to be usable. L and 2 foot dish aren't really compatible. I don't think even an offset feed will help. I will ask Tom and others to comment on the feasibility of this. I let this slip right past me when I was thinking about the alternatives. L would seem to require two separate antennas and I am loathe to go there.
It is irrelevant where the phase noise arises, on the spacecraft or on the ground. The convolution of all of the sources from the spacecraft transmitter through the receiver LO's and samplers on the ground will lead to a system cumulative noise rise due to oscillator phase noise irrespective of where the contribution arises. We might be able to overcome this on the spacecraft with more transmit power but then we have to figure out what to do with the extra heat . The heat was already going to be larger for X if we assumed perfect phase noise LO because of the lower efficiency of those devices. We still need a certain EIRP to close the link and lower efficiency does not lower the requirement to emit a certain EIRP. Since there is a fixed power budget given the proposed size, we would have to take power from the linear transponder, etc. we seem to be working to protect. The greatly increased pointing requirements on the spacecraft and ground (with 4 times as many elements on power amplifiers needed on the spacecraft for the phased array) given our constant aperture solution, coupled with lower efficiency leading to increased DC power consumption on the spacecraft, and with the inevitably higher phase noise all seem to mitigate against attempting X. I would need to see a design with some numbers but let's just say that for now I dismiss this proposal until somebody proves my entire thinking to be way off base.
We are left with S1 and S2 as the possible uplinks for the DCP that preserves the CC&R, first responder communications system. It is the contention of Emily that U/V is a crap choice for the linear transponder. Yet P3E is including it as its primary transponder. But if we accept ther premise that we don't want to put this on U/V then that argues for L/S1 for the SDX and S2/C for the DCP and we give up on region 1 accessing our digital communications experiment and our first all microwave satellite.
All of these suggestions coming fast and furious need to slow and before finger hits the key, some consideration for how the suggestion impacts the entire system need to be undertaken as requirement 1 in your personal analysis before the suggestion hits the street.
Bob
I put in a tentative bid for almost $250,000 in the upcoming budget for engineering for the coming year but no one is going to allow to me say I need about a quarter mill, trust me. If I call Jim and he does not have your team's budget numbers (as in I have not submitted numbers either), then I am going to call you to get them (I just gave myself a call). I am going to get some kind of SWAG at a number that includes hardware, travel, tools, and telecommunications. We are putting together a unified engineering budget that includes Eagle, P3E, Suitsat II, etc. so these numbers are needed.
On our system recommendation, I am going to get a decision on the overall plan before the board meeting as to the final form of our recommendation so Jim can present that to board. If this decision must be made by one or two people, so be it. We are going to decide on the system by then. PERIOD. If you have a dog in this fight, give that cur a kick in the rear.
John B. Stephensen wrote:
I'm guessing that a worldwide ITU allocation results more availability than when one region is excluded. I beleive that Bob has asked for hard information on non-availability of S1 in countries outside the U.S. Perhaps the question should cover the entire microwave spectrum.
73,
John KD6OZH
----- Original Message ----- From: "Lee McLamb" [email protected] To: "'EAGLE'" [email protected] Sent: Friday, September 15, 2006 22:59 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
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
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
-- 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 [email protected] http://amsat.org/mailman/listinfo/eagle
John,
Argentina has not recently banned all kinds of amateur transmissions on 2.4 GHz. This goes way back... 25 years ago at least. The reason I think was because that frequency was used for mobile-studio analog TV links. That service has been moved to OFDM on another frequency not long ago, but the amateur restriction still remains.
The important message here is that the TX prohibition has no connection with the proliferation of spread spectrum license-free devices, because it existed even before I used for the first time a Tandy TRS80.
73, Marc N2UO
--- "John B. Stephensen" [email protected] wrote:
Has Agrentina banned transmission on S1 for all amateur services -- terrestrial, earth and space stations?
Are we all still agreed that the primary analog and digital transponders must provide access over 75% of the orbit for ground stations using the minimum antenna/uplink power configuration?
73,
John KD6OZH
__________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "'EAGLE'" [email protected] Sent: Saturday, September 16, 2006 13:10 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Outside of finding hard proof that S1 is unavailable in LU, I have not found another example and no one has emailed me their input saying anything to the contrary. I believe that we are going to have to do this study ourselves.
L is not a solution for the primary uplink for the DCP because of the CC&R antenna. I do not believe we can feed a conventional 60cm dish with a dual band feed that includes L. The aperture efficiency on C would drop too low to use even if we could get the L band feed to be usable. L and 2 foot dish aren't really compatible. I don't think even an offset feed will help. I will ask Tom and others to comment on the feasibility of this. I let this slip right past me when I was thinking about the alternatives. L would seem to require two separate antennas and I am loathe to go there.
It is irrelevant where the phase noise arises, on the spacecraft or on the ground. The convolution of all of the sources from the spacecraft transmitter through the receiver LO's and samplers on the ground will lead to a system cumulative noise rise due to oscillator phase noise irrespective of where the contribution arises. We might be able to overcome this on the spacecraft with more transmit power but then we have to figure out what to do with the extra heat . The heat was already going to be larger for X if we assumed perfect phase noise LO because of the lower efficiency of those devices. We still need a certain EIRP to close the link and lower efficiency does not lower the requirement to emit a certain EIRP. Since there is a fixed power budget given the proposed size, we would have to take power from the linear transponder, etc. we seem to be working to protect. The greatly increased pointing requirements on the spacecraft and ground (with 4 times as many elements on power amplifiers needed on the spacecraft for the phased array) given our constant aperture solution, coupled with lower efficiency leading to increased DC power consumption on the spacecraft, and with the inevitably higher phase noise all seem to mitigate against attempting X. I would need to see a design with some numbers but let's just say that for now I dismiss this proposal until somebody proves my entire thinking to be way off base.
We are left with S1 and S2 as the possible uplinks for the DCP that preserves the CC&R, first responder communications system. It is the contention of Emily that U/V is a crap choice for the linear transponder. Yet P3E is including it as its primary transponder. But if we accept ther premise that we don't want to put this on U/V then that argues for L/S1 for the SDX and S2/C for the DCP and we give up on region 1 accessing our digital communications experiment and our first all microwave satellite.
All of these suggestions coming fast and furious need to slow and before finger hits the key, some consideration for how the suggestion impacts the entire system need to be undertaken as requirement 1 in your personal analysis before the suggestion hits the street.
Bob
I put in a tentative bid for almost $250,000 in the upcoming budget for engineering for the coming year but no one is going to allow to me say I need about a quarter mill, trust me. If I call Jim and he does not have your team's budget numbers (as in I have not submitted numbers either), then I am going to call you to get them (I just gave myself a call). I am going to get some kind of SWAG at a number that includes hardware, travel, tools, and telecommunications. We are putting together a unified engineering budget that includes Eagle, P3E, Suitsat II, etc. so these numbers are needed.
On our system recommendation, I am going to get a decision on the overall plan before the board meeting as to the final form of our recommendation so Jim can present that to board. If this decision must be made by one or two people, so be it. We are going to decide on the system by then. PERIOD. If you have a dog in this fight, give that cur a kick in the rear.
John B. Stephensen wrote:
I'm guessing that a worldwide ITU allocation results more availability than when one region is excluded. I beleive that Bob has asked for hard information on non-availability of S1 in countries outside the U.S. Perhaps the question should cover the entire microwave spectrum.
73,
John KD6OZH
----- Original Message ----- From: "Lee McLamb" [email protected] To: "'EAGLE'" [email protected] Sent: Friday, September 15, 2006 22:59 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
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
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
-- 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
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My direct experience is, however, that L uplink on AO-40 was far better using a 1.2m dish than using two 22 element Yagi antennas on that band, either collinear or CP. This is as published in QST.
Dick Jansson --------------------------- [email protected] ---------------------------
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John B. Stephensen Sent: Sunday, 17 September, 2006 1629 To: Robert McGwier; 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
-
The consideration that John has made for an X band downlink is fraught by practical issues. The specific one that I address is that of the transmitter power dissipation. He proposes a 60W DC input to 36 amplifiers with an 18W RF output. Leaving 42W to be dissipated in a rather small area, which looked like an area of no more than 0.10m^2 (~>300mm each side of a square).
To grasp the magnitude of such a thermal issue that John's plan presents, let us examine the results of his plan. The proposed dissipation amounts to a heat flux of 0.42W/cm^2. If all of this had to be radiated to space on only one side, a ridiculous solution, the temperatures would achieve levels in the range of: Ta = 534K or 261°C. Presume then that only half of the 42W is directly radiated to space, the other half removed to the spaceframe, the temperature of the array would then come down to only: Ta = 449K or 176°C.
It is clear that such a plan as John proposes cannot be achieved without a pretty involved heat pipe cooling system, not just in a line but over an area. To me such a system is a bit mind boggling. I am not rejecting heat pipes, I worked them for AO-40, but such a system is very rapidly running away from one of the primary tenets of Eagle, that of KISS.
It is easy for you to toss around antenna gains, noise factors, path losses, and the like, but sometimes consideration of these factors seem to loose sight of a practical satellite system where it actually has to be constructed in real hardware and suffer the ramifications of real hardware.
Dick Jansson --------------------------- [email protected] ---------------------------
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John B. Stephensen Sent: Sunday, 17 September, 2006 1629 To: Robert McGwier; 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
Since was asked to design the L-band receiver and many ASMAT members now seem to prefer L/S to U/V, I decided to have a look at the requirements. The attached document discusses making a L uplink that perfoms as well as the U uplink. It also looks at the S downlink.
73,
John KD6OZH
----- Original Message ----- From: "John B. Stephensen" [email protected] To: "Robert McGwier" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 16:29 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "'EAGLE'" [email protected] Sent: Saturday, September 16, 2006 13:10 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Outside of finding hard proof that S1 is unavailable in LU, I have not found another example and no one has emailed me their input saying anything to the contrary. I believe that we are going to have to do this study ourselves.
L is not a solution for the primary uplink for the DCP because of the CC&R antenna. I do not believe we can feed a conventional 60cm dish with a dual band feed that includes L. The aperture efficiency on C would drop too low to use even if we could get the L band feed to be usable. L and 2 foot dish aren't really compatible. I don't think even an offset feed will help. I will ask Tom and others to comment on the feasibility of this. I let this slip right past me when I was thinking about the alternatives. L would seem to require two separate antennas and I am loathe to go there.
It is irrelevant where the phase noise arises, on the spacecraft or on the ground. The convolution of all of the sources from the spacecraft transmitter through the receiver LO's and samplers on the ground will lead to a system cumulative noise rise due to oscillator phase noise irrespective of where the contribution arises. We might be able to overcome this on the spacecraft with more transmit power but then we have to figure out what to do with the extra heat . The heat was already going to be larger for X if we assumed perfect phase noise LO because of the lower efficiency of those devices. We still need a certain EIRP to close the link and lower efficiency does not lower the requirement to emit a certain EIRP. Since there is a fixed power budget given the proposed size, we would have to take power from the linear transponder, etc. we seem to be working to protect. The greatly increased pointing requirements on the spacecraft and ground (with 4 times as many elements on power amplifiers needed on the spacecraft for the phased array) given our constant aperture solution, coupled with lower efficiency leading to increased DC power consumption on the spacecraft, and with the inevitably higher phase noise all seem to mitigate against attempting X. I would need to see a design with some numbers but let's just say that for now I dismiss this proposal until somebody proves my entire thinking to be way off base.
We are left with S1 and S2 as the possible uplinks for the DCP that preserves the CC&R, first responder communications system. It is the contention of Emily that U/V is a crap choice for the linear transponder. Yet P3E is including it as its primary transponder. But if we accept ther premise that we don't want to put this on U/V then that argues for L/S1 for the SDX and S2/C for the DCP and we give up on region 1 accessing our digital communications experiment and our first all microwave satellite.
All of these suggestions coming fast and furious need to slow and before finger hits the key, some consideration for how the suggestion impacts the entire system need to be undertaken as requirement 1 in your personal analysis before the suggestion hits the street.
Bob
I put in a tentative bid for almost $250,000 in the upcoming budget for engineering for the coming year but no one is going to allow to me say I need about a quarter mill, trust me. If I call Jim and he does not have your team's budget numbers (as in I have not submitted numbers either), then I am going to call you to get them (I just gave myself a call). I am going to get some kind of SWAG at a number that includes hardware, travel, tools, and telecommunications. We are putting together a unified engineering budget that includes Eagle, P3E, Suitsat II, etc. so these numbers are needed.
On our system recommendation, I am going to get a decision on the overall plan before the board meeting as to the final form of our recommendation so Jim can present that to board. If this decision must be made by one or two people, so be it. We are going to decide on the system by then. PERIOD. If you have a dog in this fight, give that cur a kick in the rear.
John B. Stephensen wrote:
I'm guessing that a worldwide ITU allocation results more availability than when one region is excluded. I beleive that Bob has asked for hard information on non-availability of S1 in countries outside the U.S. Perhaps the question should cover the entire microwave spectrum.
73,
John KD6OZH
----- Original Message ----- From: "Lee McLamb" [email protected] To: "'EAGLE'" [email protected] Sent: Friday, September 15, 2006 22:59 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
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-- 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
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--------------------------------------------------------------------------------
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If the X-band PAs occupy a 30 x 30 cm area, isn't the dissipation 42/900 or 47 mW/cm^2? This would result in 1/10 the temperature rise.
73,
John KD6OZH
----- Original Message ----- From: "Dick Jansson-rr" [email protected] To: "'John B. Stephensen'" [email protected]; "'Robert McGwier'" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 18:35 UTC Subject: RE: [eagle] Re: C-C Rider Band Plan Follow-up
The consideration that John has made for an X band downlink is fraught by practical issues. The specific one that I address is that of the transmitter power dissipation. He proposes a 60W DC input to 36 amplifiers with an 18W RF output. Leaving 42W to be dissipated in a rather small area, which looked like an area of no more than 0.10m^2 (~>300mm each side of a square).
To grasp the magnitude of such a thermal issue that John's plan presents, let us examine the results of his plan. The proposed dissipation amounts to a heat flux of 0.42W/cm^2. If all of this had to be radiated to space on only one side, a ridiculous solution, the temperatures would achieve levels in the range of: Ta = 534K or 261°C. Presume then that only half of the 42W is directly radiated to space, the other half removed to the spaceframe, the temperature of the array would then come down to only: Ta = 449K or 176°C.
It is clear that such a plan as John proposes cannot be achieved without a pretty involved heat pipe cooling system, not just in a line but over an area. To me such a system is a bit mind boggling. I am not rejecting heat pipes, I worked them for AO-40, but such a system is very rapidly running away from one of the primary tenets of Eagle, that of KISS.
It is easy for you to toss around antenna gains, noise factors, path losses, and the like, but sometimes consideration of these factors seem to loose sight of a practical satellite system where it actually has to be constructed in real hardware and suffer the ramifications of real hardware.
Dick Jansson --------------------------- [email protected] ---------------------------
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John B. Stephensen Sent: Sunday, 17 September, 2006 1629 To: Robert McGwier; 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
Guenther Meisse conducted a survey for AMSAT on member preferences. That data would be more useful than anyone's anecdotes based on a few received emails, phone calls, and amsat-bb dreck.
I would like for us to concentrate on the engineering and then factor in the political choices between L,S1,S2,C. A decision is coming and soon.
Bob
John B. Stephensen wrote:
If the X-band PAs occupy a 30 x 30 cm area, isn't the dissipation 42/900 or 47 mW/cm^2? This would result in 1/10 the temperature rise.
73,
John KD6OZH
----- Original Message ----- From: "Dick Jansson-rr" [email protected] To: "'John B. Stephensen'" [email protected]; "'Robert McGwier'" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 18:35 UTC Subject: RE: [eagle] Re: C-C Rider Band Plan Follow-up
The consideration that John has made for an X band downlink is fraught by practical issues. The specific one that I address is that of the transmitter power dissipation. He proposes a 60W DC input to 36 amplifiers with an 18W RF output. Leaving 42W to be dissipated in a rather small area, which looked like an area of no more than 0.10m^2 (~>300mm each side of a square).
To grasp the magnitude of such a thermal issue that John's plan presents, let us examine the results of his plan. The proposed dissipation amounts to a heat flux of 0.42W/cm^2. If all of this had to be radiated to space on only one side, a ridiculous solution, the temperatures would achieve levels in the range of: Ta = 534K or 261°C. Presume then that only half of the 42W is directly radiated to space, the other half removed to the spaceframe, the temperature of the array would then come down to only: Ta = 449K or 176°C.
It is clear that such a plan as John proposes cannot be achieved without a pretty involved heat pipe cooling system, not just in a line but over an area. To me such a system is a bit mind boggling. I am not rejecting heat pipes, I worked them for AO-40, but such a system is very rapidly running away from one of the primary tenets of Eagle, that of KISS.
It is easy for you to toss around antenna gains, noise factors, path losses, and the like, but sometimes consideration of these factors seem to loose sight of a practical satellite system where it actually has to be constructed in real hardware and suffer the ramifications of real hardware.
Dick Jansson
[email protected]
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John B. Stephensen Sent: Sunday, 17 September, 2006 1629 To: Robert McGwier; 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
John, et.al:
I have sinned against you, by means of my erroneous calculations by an a darned decimal point! I apparently used an area of 100cm^2 whereas it should have been 1000cm^2. Sigh! I apologize for this misstep. Thanks for the correction.
The adjusted numbers are: An area of 31.6x31.6 cm is 1000cm^2 and with a dissipation of 42W, and emittance of 0.81, a power dissipation of 42W, an added solar input of ~14W, would create a device temperature of: Ta = 332K or 59°C With no transfer to the spaceframe. Presuming that the spaceframe would take perhaps 20W of the 42W, add the solar input of 14W, then: Ta = 298K or 24°C. These start to become manageable conditions, but achieving such results will still require some VERY careful thermal design of the devices and arrays, it is not a piece of cake.
Dick Jansson --------------------------- [email protected] ---------------------------
-----Original Message----- From: John B. Stephensen [mailto:[email protected]] Sent: Monday, 18 September, 2006 0854 To: Dick Jansson-rr; 'Robert McGwier'; 'EAGLE' Subject: Re: [eagle] Re: C-C Rider Band Plan Follow-up
If the X-band PAs occupy a 30 x 30 cm area, isn't the dissipation 42/900 or 47 mW/cm^2? This would result in 1/10 the temperature rise.
73,
John KD6OZH
----- Original Message ----- From: "Dick Jansson-rr" [email protected] To: "'John B. Stephensen'" [email protected]; "'Robert McGwier'" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 18:35 UTC Subject: RE: [eagle] Re: C-C Rider Band Plan Follow-up
The consideration that John has made for an X band downlink is fraught by practical issues. The specific one that I address is that of the transmitter power dissipation. He proposes a 60W DC input to 36 amplifiers with an 18W RF output. Leaving 42W to be dissipated in a rather small area, which looked like an area of no more than 0.10m^2 (~>300mm each side of a square).
To grasp the magnitude of such a thermal issue that John's plan presents, let us examine the results of his plan. The proposed dissipation amounts to a heat flux of 0.42W/cm^2. If all of this had to be radiated to space on only one side, a ridiculous solution, the temperatures would achieve levels in the range of: Ta = 534K or 261°C. Presume then that only half of the 42W is directly radiated to space, the other half removed to the spaceframe, the temperature of the array would then come down to only: Ta = 449K or 176°C.
It is clear that such a plan as John proposes cannot be achieved without a pretty involved heat pipe cooling system, not just in a line but over an area. To me such a system is a bit mind boggling. I am not rejecting heat pipes, I worked them for AO-40, but such a system is very rapidly running away from one of the primary tenets of Eagle, that of KISS.
It is easy for you to toss around antenna gains, noise factors, path losses, and the like, but sometimes consideration of these factors seem to loose sight of a practical satellite system where it actually has to be constructed in real hardware and suffer the ramifications of real hardware.
Dick Jansson --------------------------- [email protected] ---------------------------
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John B. Stephensen Sent: Sunday, 17 September, 2006 1629 To: Robert McGwier; 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
FYI I have attached a copy of that study. I would point out that people often do not respond positively to new concepts they do not truly understand the application of, or long term possibilities of. With other words, many of the responses are based solely on PAST experience and might lack VISION. Regards, Gunther
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Robert McGwier Sent: Monday, September 18, 2006 9:35 AM To: John B. Stephensen Cc: 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Guenther Meisse conducted a survey for AMSAT on member preferences. That data would be more useful than anyone's anecdotes based on a few received emails, phone calls, and amsat-bb dreck.
I would like for us to concentrate on the engineering and then factor in the political choices between L,S1,S2,C. A decision is coming and soon.
Bob
John B. Stephensen wrote:
If the X-band PAs occupy a 30 x 30 cm area, isn't the dissipation 42/900 or 47 mW/cm^2? This would result in 1/10 the temperature rise.
73,
John KD6OZH
----- Original Message ----- From: "Dick Jansson-rr" [email protected] To: "'John B. Stephensen'" [email protected]; "'Robert McGwier'" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 18:35 UTC Subject: RE: [eagle] Re: C-C Rider Band Plan Follow-up
The consideration that John has made for an X band downlink is fraught by practical issues. The specific one that I address is that of the transmitter power dissipation. He proposes a 60W DC input to 36 amplifiers with an 18W RF output. Leaving 42W to be dissipated in a rather small area, which looked like an area of no more than 0.10m^2 (~>300mm each side of a square).
To grasp the magnitude of such a thermal issue that John's plan presents, let us examine the results of his plan. The proposed dissipation amounts to a heat flux of 0.42W/cm^2. If all of this had to be radiated to space on only one side, a ridiculous solution, the temperatures would achieve levels in the range of: Ta = 534K or 261°C. Presume then that only half of the 42W is directly radiated to space, the other half removed to the spaceframe, the temperature of the array would then come down to only: Ta = 449K or 176°C.
It is clear that such a plan as John proposes cannot be achieved without a pretty involved heat pipe cooling system, not just in a line but over an area. To me such a system is a bit mind boggling. I am not rejecting heat pipes, I worked them for AO-40, but such a system is very rapidly running away from one of the primary tenets of Eagle, that of
KISS.
It is easy for you to toss around antenna gains, noise factors, path losses, and the like, but sometimes consideration of these factors seem to loose sight of a practical satellite system where it actually has to be constructed in real hardware and suffer the ramifications of real hardware.
Dick Jansson
[email protected]
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John B. Stephensen Sent: Sunday, 17 September, 2006 1629 To: Robert McGwier; 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
-- 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 [email protected] http://amsat.org/mailman/listinfo/eagle
Mode J (V/U) scored higher than I thought it would.
73,
John KD6OZH
----- Original Message ----- From: "Gunther Meisse" [email protected] To: "'Robert McGwier'" [email protected]; "'John B. Stephensen'" [email protected] Cc: "'EAGLE'" [email protected] Sent: Monday, September 18, 2006 14:43 UTC Subject: RE: [eagle] Re: C-C Rider Band Plan Follow-up
FYI I have attached a copy of that study. I would point out that people often do not respond positively to new concepts they do not truly understand the application of, or long term possibilities of. With other words, many of the responses are based solely on PAST experience and might lack VISION. Regards, Gunther
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of Robert McGwier Sent: Monday, September 18, 2006 9:35 AM To: John B. Stephensen Cc: 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Guenther Meisse conducted a survey for AMSAT on member preferences. That data would be more useful than anyone's anecdotes based on a few received emails, phone calls, and amsat-bb dreck.
I would like for us to concentrate on the engineering and then factor in the political choices between L,S1,S2,C. A decision is coming and soon.
Bob
John B. Stephensen wrote:
If the X-band PAs occupy a 30 x 30 cm area, isn't the dissipation 42/900 or 47 mW/cm^2? This would result in 1/10 the temperature rise.
73,
John KD6OZH
----- Original Message ----- From: "Dick Jansson-rr" [email protected] To: "'John B. Stephensen'" [email protected]; "'Robert McGwier'" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 18:35 UTC Subject: RE: [eagle] Re: C-C Rider Band Plan Follow-up
The consideration that John has made for an X band downlink is fraught by practical issues. The specific one that I address is that of the transmitter power dissipation. He proposes a 60W DC input to 36 amplifiers with an 18W RF output. Leaving 42W to be dissipated in a rather small area, which looked like an area of no more than 0.10m^2 (~>300mm each side of a square).
To grasp the magnitude of such a thermal issue that John's plan presents, let us examine the results of his plan. The proposed dissipation amounts to a heat flux of 0.42W/cm^2. If all of this had to be radiated to space on only one side, a ridiculous solution, the temperatures would achieve levels in the range of: Ta = 534K or 261°C. Presume then that only half of the 42W is directly radiated to space, the other half removed to the spaceframe, the temperature of the array would then come down to only: Ta = 449K or 176°C.
It is clear that such a plan as John proposes cannot be achieved without a pretty involved heat pipe cooling system, not just in a line but over an area. To me such a system is a bit mind boggling. I am not rejecting heat pipes, I worked them for AO-40, but such a system is very rapidly running away from one of the primary tenets of Eagle, that of
KISS.
It is easy for you to toss around antenna gains, noise factors, path losses, and the like, but sometimes consideration of these factors seem to loose sight of a practical satellite system where it actually has to be constructed in real hardware and suffer the ramifications of real hardware.
Dick Jansson
[email protected]
-----Original Message----- From: [email protected] [mailto:[email protected]] On Behalf Of John B. Stephensen Sent: Sunday, 17 September, 2006 1629 To: Robert McGwier; 'EAGLE' Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
-- 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 [email protected] http://amsat.org/mailman/listinfo/eagle
This is an updated version of the comparison of L/S and V/U transponders. I corrected text that implying that electrical beam-steering was possible for analog downlinks. This turns out to be harder for analog than digital as it requires one HELAPS amplifier per antenna element rather than a couple of ICs per antenna element. I've also added information on V and S downlink operation in residential areas. The lack of beamsteering will limit S downlink availability. Also note that the large receive antenna size makes S downlinks impossible in residential areas where homeowner's association approval is required.
73,
John KD6OZH
----- Original Message ----- From: "John B. Stephensen" [email protected] To: "Robert McGwier" [email protected]; "'EAGLE'" [email protected] Sent: Monday, September 18, 2006 08:47 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Since was asked to design the L-band receiver and many ASMAT members now seem to prefer L/S to U/V, I decided to have a look at the requirements. The attached document discusses making a L uplink that perfoms as well as the U uplink. It also looks at the S downlink.
73,
John KD6OZH
----- Original Message ----- From: "John B. Stephensen" [email protected] To: "Robert McGwier" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 16:29 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "'EAGLE'" [email protected] Sent: Saturday, September 16, 2006 13:10 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Outside of finding hard proof that S1 is unavailable in LU, I have not found another example and no one has emailed me their input saying anything to the contrary. I believe that we are going to have to do this study ourselves.
L is not a solution for the primary uplink for the DCP because of the CC&R antenna. I do not believe we can feed a conventional 60cm dish with a dual band feed that includes L. The aperture efficiency on C would drop too low to use even if we could get the L band feed to be usable. L and 2 foot dish aren't really compatible. I don't think even an offset feed will help. I will ask Tom and others to comment on the feasibility of this. I let this slip right past me when I was thinking about the alternatives. L would seem to require two separate antennas and I am loathe to go there.
It is irrelevant where the phase noise arises, on the spacecraft or on the ground. The convolution of all of the sources from the spacecraft transmitter through the receiver LO's and samplers on the ground will lead to a system cumulative noise rise due to oscillator phase noise irrespective of where the contribution arises. We might be able to overcome this on the spacecraft with more transmit power but then we have to figure out what to do with the extra heat . The heat was already going to be larger for X if we assumed perfect phase noise LO because of the lower efficiency of those devices. We still need a certain EIRP to close the link and lower efficiency does not lower the requirement to emit a certain EIRP. Since there is a fixed power budget given the proposed size, we would have to take power from the linear transponder, etc. we seem to be working to protect. The greatly increased pointing requirements on the spacecraft and ground (with 4 times as many elements on power amplifiers needed on the spacecraft for the phased array) given our constant aperture solution, coupled with lower efficiency leading to increased DC power consumption on the spacecraft, and with the inevitably higher phase noise all seem to mitigate against attempting X. I would need to see a design with some numbers but let's just say that for now I dismiss this proposal until somebody proves my entire thinking to be way off base.
We are left with S1 and S2 as the possible uplinks for the DCP that preserves the CC&R, first responder communications system. It is the contention of Emily that U/V is a crap choice for the linear transponder. Yet P3E is including it as its primary transponder. But if we accept ther premise that we don't want to put this on U/V then that argues for L/S1 for the SDX and S2/C for the DCP and we give up on region 1 accessing our digital communications experiment and our first all microwave satellite.
All of these suggestions coming fast and furious need to slow and before finger hits the key, some consideration for how the suggestion impacts the entire system need to be undertaken as requirement 1 in your personal analysis before the suggestion hits the street.
Bob
I put in a tentative bid for almost $250,000 in the upcoming budget for engineering for the coming year but no one is going to allow to me say I need about a quarter mill, trust me. If I call Jim and he does not have your team's budget numbers (as in I have not submitted numbers either), then I am going to call you to get them (I just gave myself a call). I am going to get some kind of SWAG at a number that includes hardware, travel, tools, and telecommunications. We are putting together a unified engineering budget that includes Eagle, P3E, Suitsat II, etc. so these numbers are needed.
On our system recommendation, I am going to get a decision on the overall plan before the board meeting as to the final form of our recommendation so Jim can present that to board. If this decision must be made by one or two people, so be it. We are going to decide on the system by then. PERIOD. If you have a dog in this fight, give that cur a kick in the rear.
John B. Stephensen wrote:
I'm guessing that a worldwide ITU allocation results more availability than when one region is excluded. I beleive that Bob has asked for hard information on non-availability of S1 in countries outside the U.S. Perhaps the question should cover the entire microwave spectrum.
73,
John KD6OZH
----- Original Message ----- From: "Lee McLamb" [email protected] To: "'EAGLE'" [email protected] Sent: Friday, September 15, 2006 22:59 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
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
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
-- 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 [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
--------------------------------------------------------------------------------
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A key issue in any satellite is power consumption, so I've updated the C/X transponder document to compare the estimated X downlink power requirements with C downlink DC power requirements for the same RF power output. 30 W more DC power is required.
73,
John KD6OZH
----- Original Message ----- From: "John B. Stephensen" [email protected] To: "Robert McGwier" [email protected]; "'EAGLE'" [email protected] Sent: Sunday, September 17, 2006 16:29 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
I agree that a 2-foot dish is useless at 1.26 GHz as it's slightly more than 2-wavelengths in diameter. S-band barely works at 4.5-wavelengths.
A C/X transponder seems feasible as there are efficient 500 mW X-band amplifier MMICs available. See the attached document.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" [email protected] To: "'EAGLE'" [email protected] Sent: Saturday, September 16, 2006 13:10 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
Outside of finding hard proof that S1 is unavailable in LU, I have not found another example and no one has emailed me their input saying anything to the contrary. I believe that we are going to have to do this study ourselves.
L is not a solution for the primary uplink for the DCP because of the CC&R antenna. I do not believe we can feed a conventional 60cm dish with a dual band feed that includes L. The aperture efficiency on C would drop too low to use even if we could get the L band feed to be usable. L and 2 foot dish aren't really compatible. I don't think even an offset feed will help. I will ask Tom and others to comment on the feasibility of this. I let this slip right past me when I was thinking about the alternatives. L would seem to require two separate antennas and I am loathe to go there.
It is irrelevant where the phase noise arises, on the spacecraft or on the ground. The convolution of all of the sources from the spacecraft transmitter through the receiver LO's and samplers on the ground will lead to a system cumulative noise rise due to oscillator phase noise irrespective of where the contribution arises. We might be able to overcome this on the spacecraft with more transmit power but then we have to figure out what to do with the extra heat . The heat was already going to be larger for X if we assumed perfect phase noise LO because of the lower efficiency of those devices. We still need a certain EIRP to close the link and lower efficiency does not lower the requirement to emit a certain EIRP. Since there is a fixed power budget given the proposed size, we would have to take power from the linear transponder, etc. we seem to be working to protect. The greatly increased pointing requirements on the spacecraft and ground (with 4 times as many elements on power amplifiers needed on the spacecraft for the phased array) given our constant aperture solution, coupled with lower efficiency leading to increased DC power consumption on the spacecraft, and with the inevitably higher phase noise all seem to mitigate against attempting X. I would need to see a design with some numbers but let's just say that for now I dismiss this proposal until somebody proves my entire thinking to be way off base.
We are left with S1 and S2 as the possible uplinks for the DCP that preserves the CC&R, first responder communications system. It is the contention of Emily that U/V is a crap choice for the linear transponder. Yet P3E is including it as its primary transponder. But if we accept ther premise that we don't want to put this on U/V then that argues for L/S1 for the SDX and S2/C for the DCP and we give up on region 1 accessing our digital communications experiment and our first all microwave satellite.
All of these suggestions coming fast and furious need to slow and before finger hits the key, some consideration for how the suggestion impacts the entire system need to be undertaken as requirement 1 in your personal analysis before the suggestion hits the street.
Bob
I put in a tentative bid for almost $250,000 in the upcoming budget for engineering for the coming year but no one is going to allow to me say I need about a quarter mill, trust me. If I call Jim and he does not have your team's budget numbers (as in I have not submitted numbers either), then I am going to call you to get them (I just gave myself a call). I am going to get some kind of SWAG at a number that includes hardware, travel, tools, and telecommunications. We are putting together a unified engineering budget that includes Eagle, P3E, Suitsat II, etc. so these numbers are needed.
On our system recommendation, I am going to get a decision on the overall plan before the board meeting as to the final form of our recommendation so Jim can present that to board. If this decision must be made by one or two people, so be it. We are going to decide on the system by then. PERIOD. If you have a dog in this fight, give that cur a kick in the rear.
John B. Stephensen wrote:
I'm guessing that a worldwide ITU allocation results more availability than when one region is excluded. I beleive that Bob has asked for hard information on non-availability of S1 in countries outside the U.S. Perhaps the question should cover the entire microwave spectrum.
73,
John KD6OZH
----- Original Message ----- From: "Lee McLamb" [email protected] To: "'EAGLE'" [email protected] Sent: Friday, September 15, 2006 22:59 UTC Subject: [eagle] Re: C-C Rider Band Plan Follow-up
We also (re)learned after the fact that ITU allocation by region isn't the same as the individual countries allowing use within their borders. As a result S1 as an uplink doesn't really solve the problem of world-wide access either. Given that experience, how confident are we that C/X would be any more or less accessable?
From what I've seen so far, Rick's proposal appears to strike a very
reasonable balance. Perhaps compiling a database of band authorizations by country would be a good project for AMSAT-International.
73, Lee-McLamb
On Fri, 2006-09-15 at 10:14 -0400, Rick Hambly (W2GPS) wrote:
John,
You say "I still like S1/C, but if there is decision that it isn't feasible for non-technical reasons and we can't be absolutely certain that L/C will remain available everywhere through 2030, C/X is better than LS2/C by providing better worldwide availablity [sic] of the satellite."
My proposal (S2/C primary + L/C at apogee) is based on the best technical solution, as recognized at SDO, with mitigation for the political issues. I feel that if we abandon this opportunity to use the best band for the job, S2, we will never solve the Region 1 issue and we might as well give the band back. S2 has all the advantages of S1 without the interference noise.
Rick W2GPS AMSAT LM2232
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
Via the Eagle mailing list courtesy of AMSAT-NA [email protected] http://amsat.org/mailman/listinfo/eagle
-- 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 [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
participants (7)
-
Dick Jansson-rr -
Gunther Meisse -
John B. Stephensen -
Lee McLamb -
Marc Franco -
Rick Hambly (W2GPS) -
Robert McGwier