A new opportunity (Phase 4 lite?)
In the last few weeks we have been presented with a new opportunity to launch RF platforms into space. This note will necessarily be cautious because we do not wish to do or say anything that will throw a monkey wrench into the works. More specific details than are given here will come from one voice, and that is from Rick.
This is a major development. One which will refocus some of the energy of the organization should it come to pass. That said, no one in management has proposed we stop Eagle and Jim Sanford will remain its project manager irrespective of what goes forward on the new project because we are still looking for rides for it.
The following is adapted from Rick's note to the board of directors, with comments from me (and edits). We are being asked to propose that we ride on someone else's satellite with our RF gear and antennas. The primary is not a small satellite. It will go to geosynchronous orbit. There are MULTIPLE rides being discussed but we have to get our act together for round one. The planned lifetime of the large satellite is over a decade and they have a track record of exceeding it. At the beginning of life it produces 1 kw of excess power and we are trying to ask for at least 1/3 of that because at the end of life, after years of solar degradation, that is what the primary expects it to produce as excess power. They do station keeping to maintain their subsatellite point.
They provide the ride. Thus, we do not need a motor, fuel tanks, hydrogen bottles, propellant flow assemblies, or liquid ignition units.
They provide the electricity, thus we do not need solar cells or a battery.
We will not need an attitude control system at all or even attitude sensors except for "gee whiz" like cameras or experiments.
They could easily provide us about as much space and mass as the Eagle would have consumed, BUT WE DO NOT NEED IT. Rick suggested to them that we would probably need as much antenna space as we have proposed for Eagle, and they did not blink. Mechanical constraints (moment of inertia ratios) allowing for a motor are completely out of the picture. We will be rigidly mounted to their frame and they do the work.
They will be asked to provide some thermal control for our RF modules, which will sit on the Nadir pointing side of their spacecraft, which is 3 axis stabilized, and will of course be subjected to hours in the sun and hours in the dark. A careful thermal design is required.
We will never need to point another antenna on the ground after the very first time should their payload behave. We will not need to despin a phased array at 3 rpm. WE WILL need a phased array but it will be adjusted in tiny increments on a daily basis at most. No more spin modulation unless there is some failure on their bird.
We need our very high efficiency power amplifiers, both the proposed linear and hard limiting design to be, as much as possible, producers of RF and not heat. They are offering this opportunity because they have discovered that if a goodly portion of the heat that is dumped from their solar arrays at the beginning of life is consumed in RF, light, etc., it saves them a considerable number of resources. This was one clever study by an in house engineer.
They have been given some basic technical information on our proposed payload. We, AMSAT, must get together now and provided them with real answers on our proposed payload in a formal written proposal, but they were given these rough estimates. We need to provide the follwing which includes but is not limited to:
1) Size & Mass [less than 50kg, probably closer to 20kg, no batteries, ] Antenna Configuration (space required) [they were told the same as Eagle, a 60cm per side hexagon or some equivalent] Frankly, it needs no symmetry at all. It can be completely determined by the needs of the antennas and the envelope restricting us.
2) Given that, there is no need for a very thick spacecraft since it has NOTHING in it but RF modules and computer(s).
3) Power requirements [they were told about 300 Watts]
4) Efficiency (how much power becomes heat) [we agreed to choose 0% to start thermal design] (sic, from Rick. I don't understand what needs to be calculated if we agree that we produce 300w of heat, then our body will quickly rise to a very high temperature and melt. I think they want to upper bound the thermal control needed for us. ;-) . )
5) Need for some of their on board resources to be specified and more details follow after our study.
6) They must be told a REALISTIC schedule that we can meet. That will determine what launches will be available to us and where the multiple payloads will be placed.
We do know their power bus is many times our planned voltage, and we need to decide if we or they build the power converter. This is pretty obvious because they don't want to power TWT's, etc. from 5 or 14V!!!
If we do multiple payloads with them, as is currently proposed, they would consider providing a "LAN" for us to communicate between satellites to our payloads (think direct, bird to bird interlinking). If the design study says we will not impact them greatly, they can provide us this link.
For Eagle, we have planned to use 3400-3410 MHz for Earth->Space and 5830-5850 MHz for Space->Earth. It may be necessary to switch these to be compatible with their transponders which are on nearly identical frequencies BUT IN THE OPPOSITE DIRECTION. We don't want to transmit near their receive frequencies. This raises a serious problem as Region 1 does not permit us to radiate signals from the satellite in the 3400-3410 MHz band if they can see it.
So it is clear, I will need to call engineering meetings, and more than one, in the next couple of months. We are prepared to spend the money on these meetings and bet this will be pulled off. If it looks like we really will close this deal (as in signing an MOU) then we will definitely bet the farm on it.
Right now, we probably should think we are basing the payloads initially on what has been thought of for Eagle and we need to rethink this because one thing should be crystal clear. THESE ARE NOT ADEQUATE. Think about what it will mean to have a very loud transmitter, either analog or digital, available 7/24/365.25 at the same spot in the sky. We do not have sufficient capacity in our current design, period. We would not want to do the SMS text messaging in the linear transponder, but would likely move it back to Microwave for example. This relieves the phase noise demands on the system for SMS (maybe not other considerations TBD). Also, the user antennas on the ground are fixed. We need some redesign starting from our basic payloads and then building them out to meet what capacity we think we can support but this will be the first time we have ever spent all of our power on the RF and very little on anything else!
I hope you can see that we must be both bold and professional with a dash of caution. A dash only because the probable time schedule will not allow us to pontificate for half a decade. If we pull this off, there is very little doubt in my mind that this will change not only AMSAT, but amateur radio in general, and if we do our job well, in a big way.
We must thank Lee McLamb profusely for finding out this opportunity was becoming available. Special circumstances allowed us, following his notice to us, to move VERY quickly to "go in at the top of the organization". That was done (MAN do I love low friends in high places and in this case, at the very top).
More details will follow as the okay comes from Rick. Please refrain from speculation or much gossip. I know I would be heart broken if the wrong leak or wrong public statement caused us to lose this major opportunity. I will not be entertaining a thousand questions but I do want everyone to think about the redesign of the payloads carefully to support a geosynchronous bird.
73's Bob N4HY
If this works out, it will be a big boost for amateur radio. Given the amount of power available, compatibility with their C-band uplink, regulatory issues outside region 2 and the ease of antenna pointing, a C/X transponder may have an advantage over C/S2.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" rwmcgwier@gmail.com To: "AMSAT Advisors" advisors@amsat.org Cc: "'EAGLE'" eagle@amsat.org Sent: Tuesday, July 17, 2007 21:52 UTC Subject: [eagle] A new opportunity (Phase 4 lite?)
In the last few weeks we have been presented with a new opportunity to launch RF platforms into space. This note will necessarily be cautious because we do not wish to do or say anything that will throw a monkey wrench into the works. More specific details than are given here will come from one voice, and that is from Rick.
This is a major development. One which will refocus some of the energy of the organization should it come to pass. That said, no one in management has proposed we stop Eagle and Jim Sanford will remain its project manager irrespective of what goes forward on the new project because we are still looking for rides for it.
The following is adapted from Rick's note to the board of directors, with comments from me (and edits). We are being asked to propose that we ride on someone else's satellite with our RF gear and antennas. The primary is not a small satellite. It will go to geosynchronous orbit. There are MULTIPLE rides being discussed but we have to get our act together for round one. The planned lifetime of the large satellite is over a decade and they have a track record of exceeding it. At the beginning of life it produces 1 kw of excess power and we are trying to ask for at least 1/3 of that because at the end of life, after years of solar degradation, that is what the primary expects it to produce as excess power. They do station keeping to maintain their subsatellite point.
They provide the ride. Thus, we do not need a motor, fuel tanks, hydrogen bottles, propellant flow assemblies, or liquid ignition units.
They provide the electricity, thus we do not need solar cells or a battery.
We will not need an attitude control system at all or even attitude sensors except for "gee whiz" like cameras or experiments.
They could easily provide us about as much space and mass as the Eagle would have consumed, BUT WE DO NOT NEED IT. Rick suggested to them that we would probably need as much antenna space as we have proposed for Eagle, and they did not blink. Mechanical constraints (moment of inertia ratios) allowing for a motor are completely out of the picture. We will be rigidly mounted to their frame and they do the work.
They will be asked to provide some thermal control for our RF modules, which will sit on the Nadir pointing side of their spacecraft, which is 3 axis stabilized, and will of course be subjected to hours in the sun and hours in the dark. A careful thermal design is required.
We will never need to point another antenna on the ground after the very first time should their payload behave. We will not need to despin a phased array at 3 rpm. WE WILL need a phased array but it will be adjusted in tiny increments on a daily basis at most. No more spin modulation unless there is some failure on their bird.
We need our very high efficiency power amplifiers, both the proposed linear and hard limiting design to be, as much as possible, producers of RF and not heat. They are offering this opportunity because they have discovered that if a goodly portion of the heat that is dumped from their solar arrays at the beginning of life is consumed in RF, light, etc., it saves them a considerable number of resources. This was one clever study by an in house engineer.
They have been given some basic technical information on our proposed payload. We, AMSAT, must get together now and provided them with real answers on our proposed payload in a formal written proposal, but they were given these rough estimates. We need to provide the follwing which includes but is not limited to:
- Size & Mass [less than 50kg, probably closer to 20kg, no batteries, ]
Antenna Configuration (space required) [they were told the same as Eagle, a 60cm per side hexagon or some equivalent] Frankly, it needs no symmetry at all. It can be completely determined by the needs of the antennas and the envelope restricting us.
- Given that, there is no need for a very thick spacecraft since it has
NOTHING in it but RF modules and computer(s).
Power requirements [they were told about 300 Watts]
Efficiency (how much power becomes heat) [we agreed to choose 0% to
start thermal design] (sic, from Rick. I don't understand what needs to be calculated if we agree that we produce 300w of heat, then our body will quickly rise to a very high temperature and melt. I think they want to upper bound the thermal control needed for us. ;-) . )
- Need for some of their on board resources to be specified and more
details follow after our study.
- They must be told a REALISTIC schedule that we can meet. That will
determine what launches will be available to us and where the multiple payloads will be placed.
We do know their power bus is many times our planned voltage, and we need to decide if we or they build the power converter. This is pretty obvious because they don't want to power TWT's, etc. from 5 or 14V!!!
If we do multiple payloads with them, as is currently proposed, they would consider providing a "LAN" for us to communicate between satellites to our payloads (think direct, bird to bird interlinking). If the design study says we will not impact them greatly, they can provide us this link.
For Eagle, we have planned to use 3400-3410 MHz for Earth->Space and 5830-5850 MHz for Space->Earth. It may be necessary to switch these to be compatible with their transponders which are on nearly identical frequencies BUT IN THE OPPOSITE DIRECTION. We don't want to transmit near their receive frequencies. This raises a serious problem as Region 1 does not permit us to radiate signals from the satellite in the 3400-3410 MHz band if they can see it.
So it is clear, I will need to call engineering meetings, and more than one, in the next couple of months. We are prepared to spend the money on these meetings and bet this will be pulled off. If it looks like we really will close this deal (as in signing an MOU) then we will definitely bet the farm on it.
Right now, we probably should think we are basing the payloads initially on what has been thought of for Eagle and we need to rethink this because one thing should be crystal clear. THESE ARE NOT ADEQUATE. Think about what it will mean to have a very loud transmitter, either analog or digital, available 7/24/365.25 at the same spot in the sky. We do not have sufficient capacity in our current design, period. We would not want to do the SMS text messaging in the linear transponder, but would likely move it back to Microwave for example. This relieves the phase noise demands on the system for SMS (maybe not other considerations TBD). Also, the user antennas on the ground are fixed. We need some redesign starting from our basic payloads and then building them out to meet what capacity we think we can support but this will be the first time we have ever spent all of our power on the RF and very little on anything else!
I hope you can see that we must be both bold and professional with a dash of caution. A dash only because the probable time schedule will not allow us to pontificate for half a decade. If we pull this off, there is very little doubt in my mind that this will change not only AMSAT, but amateur radio in general, and if we do our job well, in a big way.
We must thank Lee McLamb profusely for finding out this opportunity was becoming available. Special circumstances allowed us, following his notice to us, to move VERY quickly to "go in at the top of the organization". That was done (MAN do I love low friends in high places and in this case, at the very top).
More details will follow as the okay comes from Rick. Please refrain from speculation or much gossip. I know I would be heart broken if the wrong leak or wrong public statement caused us to lose this major opportunity. I will not be entertaining a thousand questions but I do want everyone to think about the redesign of the payloads carefully to support a geosynchronous bird.
73's Bob N4HY -- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
John,
I would second that! That would make it compatible with all the regions.
John B. Stephensen wrote:
If this works out, it will be a big boost for amateur radio. Given the amount of power available, compatibility with their C-band uplink, regulatory issues outside region 2 and the ease of antenna pointing, a C/X transponder may have an advantage over C/S2.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" rwmcgwier@gmail.com To: "AMSAT Advisors" advisors@amsat.org Cc: "'EAGLE'" eagle@amsat.org Sent: Tuesday, July 17, 2007 21:52 UTC Subject: [eagle] A new opportunity (Phase 4 lite?)
In the last few weeks we have been presented with a new opportunity to launch RF platforms into space. This note will necessarily be cautious because we do not wish to do or say anything that will throw a monkey wrench into the works. More specific details than are given here will come from one voice, and that is from Rick.
This is a major development. One which will refocus some of the energy of the organization should it come to pass. That said, no one in management has proposed we stop Eagle and Jim Sanford will remain its project manager irrespective of what goes forward on the new project because we are still looking for rides for it.
The following is adapted from Rick's note to the board of directors, with comments from me (and edits). We are being asked to propose that we ride on someone else's satellite with our RF gear and antennas. The primary is not a small satellite. It will go to geosynchronous orbit. There are MULTIPLE rides being discussed but we have to get our act together for round one. The planned lifetime of the large satellite is over a decade and they have a track record of exceeding it. At the beginning of life it produces 1 kw of excess power and we are trying to ask for at least 1/3 of that because at the end of life, after years of solar degradation, that is what the primary expects it to produce as excess power. They do station keeping to maintain their subsatellite point.
They provide the ride. Thus, we do not need a motor, fuel tanks, hydrogen bottles, propellant flow assemblies, or liquid ignition units.
They provide the electricity, thus we do not need solar cells or a battery.
We will not need an attitude control system at all or even attitude sensors except for "gee whiz" like cameras or experiments.
They could easily provide us about as much space and mass as the Eagle would have consumed, BUT WE DO NOT NEED IT. Rick suggested to them that we would probably need as much antenna space as we have proposed for Eagle, and they did not blink. Mechanical constraints (moment of inertia ratios) allowing for a motor are completely out of the picture. We will be rigidly mounted to their frame and they do the work.
They will be asked to provide some thermal control for our RF modules, which will sit on the Nadir pointing side of their spacecraft, which is 3 axis stabilized, and will of course be subjected to hours in the sun and hours in the dark. A careful thermal design is required.
We will never need to point another antenna on the ground after the very first time should their payload behave. We will not need to despin a phased array at 3 rpm. WE WILL need a phased array but it will be adjusted in tiny increments on a daily basis at most. No more spin modulation unless there is some failure on their bird.
We need our very high efficiency power amplifiers, both the proposed linear and hard limiting design to be, as much as possible, producers of RF and not heat. They are offering this opportunity because they have discovered that if a goodly portion of the heat that is dumped from their solar arrays at the beginning of life is consumed in RF, light, etc., it saves them a considerable number of resources. This was one clever study by an in house engineer.
They have been given some basic technical information on our proposed payload. We, AMSAT, must get together now and provided them with real answers on our proposed payload in a formal written proposal, but they were given these rough estimates. We need to provide the follwing which includes but is not limited to:
- Size & Mass [less than 50kg, probably closer to 20kg, no batteries, ]
Antenna Configuration (space required) [they were told the same as Eagle, a 60cm per side hexagon or some equivalent] Frankly, it needs no symmetry at all. It can be completely determined by the needs of the antennas and the envelope restricting us.
- Given that, there is no need for a very thick spacecraft since it has
NOTHING in it but RF modules and computer(s).
Power requirements [they were told about 300 Watts]
Efficiency (how much power becomes heat) [we agreed to choose 0% to
start thermal design] (sic, from Rick. I don't understand what needs to be calculated if we agree that we produce 300w of heat, then our body will quickly rise to a very high temperature and melt. I think they want to upper bound the thermal control needed for us. ;-) . )
- Need for some of their on board resources to be specified and more
details follow after our study.
- They must be told a REALISTIC schedule that we can meet. That will
determine what launches will be available to us and where the multiple payloads will be placed.
We do know their power bus is many times our planned voltage, and we need to decide if we or they build the power converter. This is pretty obvious because they don't want to power TWT's, etc. from 5 or 14V!!!
If we do multiple payloads with them, as is currently proposed, they would consider providing a "LAN" for us to communicate between satellites to our payloads (think direct, bird to bird interlinking). If the design study says we will not impact them greatly, they can provide us this link.
For Eagle, we have planned to use 3400-3410 MHz for Earth->Space and 5830-5850 MHz for Space->Earth. It may be necessary to switch these to be compatible with their transponders which are on nearly identical frequencies BUT IN THE OPPOSITE DIRECTION. We don't want to transmit near their receive frequencies. This raises a serious problem as Region 1 does not permit us to radiate signals from the satellite in the 3400-3410 MHz band if they can see it.
So it is clear, I will need to call engineering meetings, and more than one, in the next couple of months. We are prepared to spend the money on these meetings and bet this will be pulled off. If it looks like we really will close this deal (as in signing an MOU) then we will definitely bet the farm on it.
Right now, we probably should think we are basing the payloads initially on what has been thought of for Eagle and we need to rethink this because one thing should be crystal clear. THESE ARE NOT ADEQUATE. Think about what it will mean to have a very loud transmitter, either analog or digital, available 7/24/365.25 at the same spot in the sky. We do not have sufficient capacity in our current design, period. We would not want to do the SMS text messaging in the linear transponder, but would likely move it back to Microwave for example. This relieves the phase noise demands on the system for SMS (maybe not other considerations TBD). Also, the user antennas on the ground are fixed. We need some redesign starting from our basic payloads and then building them out to meet what capacity we think we can support but this will be the first time we have ever spent all of our power on the RF and very little on anything else!
I hope you can see that we must be both bold and professional with a dash of caution. A dash only because the probable time schedule will not allow us to pontificate for half a decade. If we pull this off, there is very little doubt in my mind that this will change not only AMSAT, but amateur radio in general, and if we do our job well, in a big way.
We must thank Lee McLamb profusely for finding out this opportunity was becoming available. Special circumstances allowed us, following his notice to us, to move VERY quickly to "go in at the top of the organization". That was done (MAN do I love low friends in high places and in this case, at the very top).
More details will follow as the okay comes from Rick. Please refrain from speculation or much gossip. I know I would be heart broken if the wrong leak or wrong public statement caused us to lose this major opportunity. I will not be entertaining a thousand questions but I do want everyone to think about the redesign of the payloads carefully to support a geosynchronous bird.
73's Bob N4HY -- AMSAT Director and VP Engineering. Member: ARRL, AMSAT-DL, TAPR, Packrats, NJQRP, QRP ARCI, QCWA, FRC. ARRL SDR WG Chair "If you're going to be crazy, you have to get paid for it or else you're going to be locked up." Hunter S. Thompson _______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
That would be under consideration and when you have all of the relevant information, we can go do the link budgets and decide if we can build it and the political and regulatory issues will factor in then.
We would still need to build a phased array because we are informed that for thermal control reasons, the satellite rocks back and forth around one or more axes at a very slow rate to try to keep the power and heat generation down on the solar panels. Both the reality and the amplitude of this rocking needs to be understood. No one more than I would like for us to found out that this is wrong and that we can expect it to be stable. BUT, I wonder if we can even afford to make that decision. It would be horrible indeed, if there were a large disaster, and our comms gear, promised to FEMA/NTIS etc. was found to be unusable because our primary had rocked the satellite for operational reasons and we had decided to put a fixed beam antenna on the platform.
On 10 Ghz: So we would try to get just enough gain to illuminate the earth but Ooooops, that won't quite get it because the path loss at X band is much higher and would not allow for the ground user terminal we would like to support. If you overcome the path loss with gain, you do not illuminate the visible earth. Any phased array we are capable of building I don't think would allow for continent shaping of the beam and if it could, would we really want to be unable to work the DX in the middle of the Pacific Ocean?
There are both technical and political reasons why the decisions made are what they are. I don't believe the reasons have changed that much but I do know we have the opportunity to revisit this and we should.
Our primary satellite owner will respond to our request for 300w and should they say yes, there is little doubt we will find a way to spend it and our job is to optimize that.
Another consideration, is that they are looking for efficiency. I do not believe you can give me the same efficiency at 10 GHz you can give me at 3.4 GHz. I believe the power flux density on 3.4 GHz will be low enough we can claim noninterference but that will have to be tested (with regulatory authorities).
Much to do!
Bob
Bill Ress wrote:
John,
I would second that! That would make it compatible with all the regions.
John B. Stephensen wrote:
If this works out, it will be a big boost for amateur radio. Given the amount of power available, compatibility with their C-band uplink, regulatory issues outside region 2 and the ease of antenna pointing, a C/X transponder may have an advantage over C/S2.
73,
John KD6OZH
Bob -
Is the back and forth rocking a reaction of the body due to [primarily] dithering the solar panel and/or yaw angle? If so, the off-pointing amplitude will likely be relatively small, considering what will likely be a large inertia ratio of the body to solar panels. The body rocking should be dampened by the reaction wheels to keep an Earth sensor reasonably centered.
It might be interesting if an actual off-nadir amplitude is available.
73, Ken Ernandes N2WWD
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Robert McGwier Sent: Friday, July 20, 2007 9:19 AM To: Bill Ress Cc: 'EAGLE' Subject: [eagle] Re: A new opportunity (Phase 4 lite?)
That would be under consideration and when you have all of the relevant information, we can go do the link budgets and decide if we can build it and the political and regulatory issues will factor in then.
We would still need to build a phased array because we are informed that for thermal control reasons, the satellite rocks back and forth around one or more axes at a very slow rate to try to keep the power and heat generation down on the solar panels. Both the reality and the amplitude of this rocking needs to be understood. No one more than I would like for us to found out that this is wrong and that we can expect it to be stable. BUT, I wonder if we can even afford to make that decision. It would be horrible indeed, if there were a large disaster, and our comms gear, promised to FEMA/NTIS etc. was found to be unusable because our primary had rocked the satellite for operational reasons and we had decided to put a fixed beam antenna on the platform.
On 10 Ghz: So we would try to get just enough gain to illuminate the earth but Ooooops, that won't quite get it because the path loss at X band is much higher and would not allow for the ground user terminal we would like to support. If you overcome the path loss with gain, you do not illuminate the visible earth. Any phased array we are capable of building I don't think would allow for continent shaping of the beam and if it could, would we really want to be unable to work the DX in the middle of the Pacific Ocean?
There are both technical and political reasons why the decisions made are what they are. I don't believe the reasons have changed that much but I do know we have the opportunity to revisit this and we should.
Our primary satellite owner will respond to our request for 300w and should they say yes, there is little doubt we will find a way to spend it and our job is to optimize that.
Another consideration, is that they are looking for efficiency. I do not believe you can give me the same efficiency at 10 GHz you can give me at 3.4 GHz. I believe the power flux density on 3.4 GHz will be low enough we can claim noninterference but that will have to be tested (with regulatory authorities).
Much to do!
Bob
Bill Ress wrote:
John,
I would second that! That would make it compatible with all the regions.
John B. Stephensen wrote:
If this works out, it will be a big boost for amateur radio. Given the amount of power available, compatibility with their C-band uplink, regulatory issues outside region 2 and the ease of antenna pointing, a
C/X
transponder may have an advantage over C/S2.
73,
John KD6OZH
The increased gain of the earth station antenna compensates for the path loss.
73,
John KD6OZH
----- Original Message ----- From: "Robert McGwier" rwmcgwier@gmail.com To: "Bill Ress" bill@hsmicrowave.com Cc: "John B. Stephensen" kd6ozh@comcast.net; "'EAGLE'" eagle@amsat.org Sent: Friday, July 20, 2007 13:18 UTC Subject: Re: [eagle] Re: A new opportunity (Phase 4 lite?)
On 10 Ghz: So we would try to get just enough gain to illuminate the earth but Ooooops, that won't quite get it because the path loss at X band is much higher and would not allow for the ground user terminal we would like to support. If you overcome the path loss with gain, you do not illuminate the visible earth. Any phased array we are capable of building I don't think would allow for continent shaping of the beam and if it could, would we really want to be unable to work the DX in the middle of the Pacific Ocean?
Bob
Here is a spectrum survey for the Los Angeles area made by the NTIA in 1995. Note the absence of signals in the 10.45-10.50 GHz band.
73,
John KD6OZH
Rick W2GPS AMSAT LM2232
Bob,
After extensive discussions over three days here at the AMSAT-UK meeting I think we will be OK with a 3.4 GHz downlink but we will need a mitigation plan in case some country complains. Complaints need to show that we are generating "harmful interference" which is unlikely especially as our downlink is wide band data. The Europeans are going to push the issue this year and possibly get some discussions going in WARC07. We mush get ARRL on the same page as they will need support from us.
There are at least three mitigation possibilities.
1) Steer the 3.4 GHz antenna away from Region 1. This will be needed in 2 and 3 below, so we will need this capability or we would have to shut down the 3.4GHz downlink.
2) Use 2.4 GHz as the Region 1 downlink. This would not be hard as we have another 2.4 GHz transmitter and merging them into one antenna can be done. I contend that we can live with the pollution on this band if we use a modest 60cm+ dish on the ground pointed up. We should do terrestrial tests with a transponder on a tower to test this.
3) Use 10GHz as the region 1 downlink. This would require a new antenna array and we would need to deal with the issues associated with the higher path loss while keeping things simple for our average users.
After the meeting I had before this trip it is not clear that we will need to steer the antenna much if at all. My previous information may have been wrong (or not).
On the 3.4 GHz and 5.6GHz bands we may be able to share existing antennas. At least that possibility was suggested. I am not so sure that this idea will stand up to technical scrutiny but it might.
I'm coming home tomorrow so I will be out of touch.
Rick W2GPS
On Sun, 2007-07-22 at 13:17, Rick Hambly (W2GPS) wrote:
- Use 10GHz as the region 1 downlink. This would require a new antenna
array and we would need to deal with the issues associated with the higher path loss while keeping things simple for our average users.
On Fri, 2007-07-20 at 17:42, John B. Stephensen wrote:
The increased gain of the earth station antenna compensates for the path loss.
Right. People say that path loss increases proportional to frequency (6 dB more path loss every time you double the frequency). But that is true only if you assume the antenna gain at both ends of the link is kept constant as you change frequency.
However, if you assume antenna APERTURE is constant with frequency, then path loss is actually INVERSELY proportional to frequency (6 dB LESS loss every time you double the frequency). In other words, for constant-size antennas, the higher the frequency the better.
So what does that mean for Eagle?
If you assume satellite antenna gain does not change with frequency (so as to keep the beam width just wide enough to illuminate the earth) and earth station aperture does not change with frequency (to keep the same dish size), then path loss is independent of frequency.
Al N1AL
I agree. This is one reason I always remove the frequency-dependent component when I do path loss analysis for a particular orbit.
73, Ken N2WWD
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Alan Bloom Sent: Monday, July 23, 2007 12:13 PM To: Rick Hambly (W2GPS) Cc: 'EAGLE' Subject: [eagle] Path loss (Was: A new opportunity (Phase 4 lite?))
On Sun, 2007-07-22 at 13:17, Rick Hambly (W2GPS) wrote:
- Use 10GHz as the region 1 downlink. This would require a new antenna
array and we would need to deal with the issues associated with the higher path loss while keeping things simple for our average users.
On Fri, 2007-07-20 at 17:42, John B. Stephensen wrote:
The increased gain of the earth station antenna compensates for the path loss.
Right. People say that path loss increases proportional to frequency (6 dB more path loss every time you double the frequency). But that is true only if you assume the antenna gain at both ends of the link is kept constant as you change frequency.
However, if you assume antenna APERTURE is constant with frequency, then path loss is actually INVERSELY proportional to frequency (6 dB LESS loss every time you double the frequency). In other words, for constant-size antennas, the higher the frequency the better.
So what does that mean for Eagle?
If you assume satellite antenna gain does not change with frequency (so as to keep the beam width just wide enough to illuminate the earth) and earth station aperture does not change with frequency (to keep the same dish size), then path loss is independent of frequency.
Al N1AL
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
Bob:
I look forward to the thermal challenges suggested by your message. If I were to conjecture on the equipment, the positioning and power levels start to suggest that the use of heat pipes might be in order to solve these problems. Heat pipe cooling of equipment is always an interesting challenge. I also remember very well my P4 work of the late 80's (nearly 20 years ago!).
'73, Dick Jansson, KD1K kd1k@amsat.org kd1k@arrl.net
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Robert McGwier Sent: Tuesday, 17 July, 2007 22.52 To: AMSAT Advisors Cc: 'EAGLE' Subject: [eagle] A new opportunity (Phase 4 lite?)
In the last few weeks we have been presented with a new opportunity to launch RF platforms into space. This note will necessarily
(snip)
Dick,
It is likely that we will have access to the host structure's thermal management system, whatever that is. We will be in sun or shade for extended periods.
Rick W2GPS AMSAT LM2232
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Dick Jansson-rr Sent: Friday, July 20, 2007 10:38 AM To: 'Robert McGwier'; 'AMSAT Advisors' Cc: 'EAGLE' Subject: [eagle] Re: A new opportunity (Phase 4 lite?)
Bob:
I look forward to the thermal challenges suggested by your message. If I were to conjecture on the equipment, the positioning and power levels start to suggest that the use of heat pipes might be in order to solve these problems. Heat pipe cooling of equipment is always an interesting challenge. I also remember very well my P4 work of the late 80's (nearly 20 years ago!).
'73, Dick Jansson, KD1K kd1k@amsat.org kd1k@arrl.net
-----Original Message----- From: eagle-bounces@amsat.org [mailto:eagle-bounces@amsat.org] On Behalf Of Robert McGwier Sent: Tuesday, 17 July, 2007 22.52 To: AMSAT Advisors Cc: 'EAGLE' Subject: [eagle] A new opportunity (Phase 4 lite?)
In the last few weeks we have been presented with a new opportunity to launch RF platforms into space. This note will necessarily
(snip)
_______________________________________________ Via the Eagle mailing list courtesy of AMSAT-NA Eagle@amsat.org http://amsat.org/mailman/listinfo/eagle
participants (7)
-
Alan Bloom -
Bill Ress -
Dick Jansson-rr -
John B. Stephensen -
Ken Ernandes -
Rick Hambly (W2GPS) -
Robert McGwier