Making the transponder sats as easy as the fm birds
I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP.
Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote:
I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP. _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
So VERY true! Thanks Bruce, ANDY w5acm
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bruce Sent: Friday, April 13, 2018 9:40 PM To: [email protected] Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm birds
Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote:
I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP. _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Hang on, I'm a bit new to this, but that does not seem 100% right. We have no control over the satellite frequency, so the ground station must adjust... that seems obvious, but maybe I missed something or maybe you're talking about satellites which are not on fixed frequency transponders ?
In any case, when the satellite is rising (or approaching), then the waves coming from it will be compressed, so RX frequency at the ground station will be higher than when it left the satellite. Since the satellite is approaching the waves hitting it from the ground station will also be compressed. So, both RX and TX will be higher in frequency.
The opposite happens when the satellite is descending (or moving away from the ground station) i.e. waves from the ground station TX stretch in chasing the satellite and waves coming into the ground station are stretched as the satellite moves away, so both TX and RX will be lower frequency.
Thus the ground station should tune up the band before the satellite appears (AOS) and should reduce frequency (both RX and TX) as the satellite rises, passes and sets. It will be above frequency at the start, on frequency right overhead and lower frequency from just past overhead to LOS.
Or did I miss the plot ?
73,
Stephen VE6SVJ SKCC # 14855 Okotoks, AB
On 13 April 2018 at 20:49, Andy [email protected] wrote:
So VERY true! Thanks Bruce, ANDY w5acm
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bruce Sent: Friday, April 13, 2018 9:40 PM To: [email protected] Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm birds
Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote:
I’ve had an idea for a long time as to making the satellites with linear
transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that
your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity
relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our
location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP. _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect
the official views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
--
Bruce Paige, KK5DO
AMSAT Director Contests and Awards AMSAT Board Member 2016-2018
ARRL Awards Field Checker (WAS, 5BWAS, VUCC), VE
Houston AMSAT Net - Wed 0100z on Echolink - Conference *AMSAT* Also live streaming MP3 at http://www.amsatnet.com Podcast at http://www.amsatnet.com/podcast.xml or iTunes
Latest satellite news on the ARRL Audio News http://www.arrl.org
AMSAT on Twitter http://www.twitter.com/amsat
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Computer control or actually a variation of such *IS* what I’m considering and proposing. Yes I have read “the one true way”. I understand this manual tweaking is how it’s currently done. Why however are we adjusting only one frequency? It seems that we can adjust the transmit frequency so that it is always the same distance from the beacon as seen by the satellite and the receiver can automatically track the subduable tone transmitted. This means that you need not drift across the transponder and the rx station automatically tracks. What am I missing in this being hands off and always on frequency?
AF6EP
Sent using SMTP.
On Apr 13, 2018, at 7:49 PM, Andy [email protected] wrote:
So VERY true! Thanks Bruce, ANDY w5acm
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bruce Sent: Friday, April 13, 2018 9:40 PM To: [email protected] Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm birds
Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote: I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP. _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
--
Bruce Paige, KK5DO
AMSAT Director Contests and Awards AMSAT Board Member 2016-2018
ARRL Awards Field Checker (WAS, 5BWAS, VUCC), VE
Houston AMSAT Net - Wed 0100z on Echolink - Conference *AMSAT* Also live streaming MP3 at http://www.amsatnet.com Podcast at http://www.amsatnet.com/podcast.xml or iTunes
Latest satellite news on the ARRL Audio News http://www.arrl.org
AMSAT on Twitter http://www.twitter.com/amsat
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
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Okay, first off, SatPC32 and other computer control software has done this exact thing for years. And it has effectively done it without sending garbage signals. There is also FlexTune which sends a tone to initially calibrate, then the rest of the Doppler corrections are done mathematically vs continuously sending garbage. Another thing of note, you're already sending your voice, why add more? The other software is initially calibrated manually then continues track with that offset automatically. Seems better than loading a transponder with even more nonsense.
Personally, I don't see why people consider the linear transponders to me so mystical. They're simple: signal goes in one point, out the other. Big whoop. To tune just use a little bit of basic math skills that a 2nd grader should possess and then turn the knobs till the voices sound right. Pretty easy, right? Instead we have people who I've never heard on any satellite (in my two years and 10,000 sat QSOs) suggesting complex and unnecessary things to make operating on these satellites "easier", when most competent ops already find them plenty easy.
73, Gabe AL6D/actuallyoperateslinearsats
On Fri, Apr 13, 2018 at 7:53 PM, Eric Fort < [email protected]> wrote:
Computer control or actually a variation of such *IS* what I’m considering and proposing. Yes I have read “the one true way”. I understand this manual tweaking is how it’s currently done. Why however are we adjusting only one frequency? It seems that we can adjust the transmit frequency so that it is always the same distance from the beacon as seen by the satellite and the receiver can automatically track the subduable tone transmitted. This means that you need not drift across the transponder and the rx station automatically tracks. What am I missing in this being hands off and always on frequency?
AF6EP
Sent using SMTP.
On Apr 13, 2018, at 7:49 PM, Andy [email protected] wrote:
So VERY true! Thanks Bruce, ANDY w5acm
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bruce Sent: Friday, April 13, 2018 9:40 PM To: [email protected] Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm
birds
Sorry, this theory of thought is incorrect. You must adjust the higher
of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote: I’ve had an idea for a long time as to making the satellites with
linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that
your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity
relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our
location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP. _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect
the official views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
--
Bruce Paige, KK5DO
AMSAT Director Contests and Awards AMSAT Board Member 2016-2018
ARRL Awards Field Checker (WAS, 5BWAS, VUCC), VE
Houston AMSAT Net - Wed 0100z on Echolink - Conference *AMSAT* Also live
streaming MP3 at http://www.amsatnet.com Podcast at http://www.amsatnet.com/podcast.xml or iTunes
Latest satellite news on the ARRL Audio News http://www.arrl.org
AMSAT on Twitter http://www.twitter.com/amsat
Sent via [email protected]. AMSAT-NA makes this open forum available
to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership.
Opinions expressed
are solely those of the author, and do not reflect the official views of
AMSAT-NA.
Not an AMSAT-NA member? Join now to support the amateur satellite
program!
Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
"subaudible" is only sub audible when you're dead on frequency if you're using SSB. For FM, where we are familiar with the technique, that's fine. But instead of a tone, you'd perhaps be better off running Single Sideband AM (i.e. a sub audible tone of zero hertz); there was a satellite recently that was in that sort of mode (I forget which bird), and it was really interesting to work.
BUT, one huge problem with sending up a "beacon tone" for aligning stations to, is that you're sending a 100% duty cycle carrier (though perhaps reduced power) to a transponder that really hates having 100% carriers run through it. That's one of the big reasons why they don't allow FM on the SSB / CW birds (the other being the extra bandwidth that it takes).
Bottom line is that, yes, one can construct methods to aid in frequency tracking. But One True Rule software-assisted operation works really well already, for those who can use it, and can be backed all the way down to manual for those who can't. And, manual operation of an SSB station through a satellite is quite an interesting exercise. I often find it more satisfying than having to deal with starting up and fussing with all the computer automation "help". Just takes a bit of practice.
Greg KO6TH
Eric Fort wrote:
Computer control or actually a variation of such *IS* what I’m considering and proposing. Yes I have read “the one true way”. I understand this manual tweaking is how it’s currently done. Why however are we adjusting only one frequency? It seems that we can adjust the transmit frequency so that it is always the same distance from the beacon as seen by the satellite and the receiver can automatically track the subduable tone transmitted. This means that you need not drift across the transponder and the rx station automatically tracks. What am I missing in this being hands off and always on frequency?
AF6EP
Sent using SMTP.
On Apr 13, 2018, at 7:49 PM, Andy [email protected] wrote:
So VERY true! Thanks Bruce, ANDY w5acm
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bruce Sent: Friday, April 13, 2018 9:40 PM To: [email protected] Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm birds
Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote: I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP. _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
--
Bruce Paige, KK5DO
AMSAT Director Contests and Awards AMSAT Board Member 2016-2018
ARRL Awards Field Checker (WAS, 5BWAS, VUCC), VE
Houston AMSAT Net - Wed 0100z on Echolink - Conference *AMSAT* Also live streaming MP3 at http://www.amsatnet.com Podcast at http://www.amsatnet.com/podcast.xml or iTunes
Latest satellite news on the ARRL Audio News http://www.arrl.org
AMSAT on Twitter http://www.twitter.com/amsat
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
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Yes, a zero hertz tone would be ideal if one were going to insert a tone for tracking. Not sure you’d need full carrier though. The advantage of a zero hertz tone is not having to notch it on rx, a ctcss tone is probably easier to generate on modern transceivers though. Having a (reduced) “carrier” to measure and track would seem to be an aid to automated tuning of the receiver though. Sound card listens for the tone and adjusts rx frequency according to the offset from a known and agreed upon transmit tone. What I’m hearing here in the comments though and I’ll ask if this is correct.... is that the computational approach of adjustment based upon published elements is good enough. Can and does the computer frequency control get us close enough for hands off operating when both stations us it?
Also if computer control and tracking is “good enough” why is it not almost universal on the transponder sats? For the cost of a Raspberry pi or similar sbc and the proper ci-v / cat cable you have computer control of frequency. As cheap as this is compared to the cost of an all mode radio why is it not more often put to use?
If computer control is not good enough for hands free operation, how can we make it so?
Af6ep
Sent using SMTP.
On Apr 13, 2018, at 10:23 PM, Greg D [email protected] wrote:
"subaudible" is only sub audible when you're dead on frequency if you're using SSB. For FM, where we are familiar with the technique, that's fine. But instead of a tone, you'd perhaps be better off running Single Sideband AM (i.e. a sub audible tone of zero hertz); there was a satellite recently that was in that sort of mode (I forget which bird), and it was really interesting to work.
BUT, one huge problem with sending up a "beacon tone" for aligning stations to, is that you're sending a 100% duty cycle carrier (though perhaps reduced power) to a transponder that really hates having 100% carriers run through it. That's one of the big reasons why they don't allow FM on the SSB / CW birds (the other being the extra bandwidth that it takes).
Bottom line is that, yes, one can construct methods to aid in frequency tracking. But One True Rule software-assisted operation works really well already, for those who can use it, and can be backed all the way down to manual for those who can't. And, manual operation of an SSB station through a satellite is quite an interesting exercise. I often find it more satisfying than having to deal with starting up and fussing with all the computer automation "help". Just takes a bit of practice.
Greg KO6TH
Eric Fort wrote:
Computer control or actually a variation of such *IS* what I’m considering and proposing. Yes I have read “the one true way”. I understand this manual tweaking is how it’s currently done. Why however are we adjusting only one frequency? It seems that we can adjust the transmit frequency so that it is always the same distance from the beacon as seen by the satellite and the receiver can automatically track the subduable tone transmitted. This means that you need not drift across the transponder and the rx station automatically tracks. What am I missing in this being hands off and always on frequency?
AF6EP
Sent using SMTP.
On Apr 13, 2018, at 7:49 PM, Andy [email protected] wrote:
So VERY true! Thanks Bruce, ANDY w5acm
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bruce Sent: Friday, April 13, 2018 9:40 PM To: [email protected] Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm birds
Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote: I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
Sent using SMTP. _______________________________________________ Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
--
Bruce Paige, KK5DO
AMSAT Director Contests and Awards AMSAT Board Member 2016-2018
ARRL Awards Field Checker (WAS, 5BWAS, VUCC), VE
Houston AMSAT Net - Wed 0100z on Echolink - Conference *AMSAT* Also live streaming MP3 at http://www.amsatnet.com Podcast at http://www.amsatnet.com/podcast.xml or iTunes
Latest satellite news on the ARRL Audio News http://www.arrl.org
AMSAT on Twitter http://www.twitter.com/amsat
Sent via [email protected]. AMSAT-NA makes this open forum available to all interested persons worldwide without requiring membership. Opinions expressed are solely those of the author, and do not reflect the official views of AMSAT-NA. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
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You are correct that a full power carrier is not needed, but still the whole exercise, while interesting to contemplate, is unnecessary for the task at hand. My opinion is that computer control is plenty good enough. Even full manual control is good enough in the hands of an experienced operator. Neither method is going to be as easy as chatting on simplex or the local repeater "out of the box";, nor do I think they need to be. Both require some knowledge, learning (which is different than book knowledge), and practice. That learning is a big part of what the hobby is all about.
Then it will be easy. It took me weeks of work and elmering to make my first satellite contact, and a lot of that success was due to the skill of the operator on the other end (Mel, KW7E). That was on RS-10, which was considered the ultimate "Easy Sat". The second contact took a lot less time, and pretty soon I could fire up the rigs, find myself, and be in business in seconds, all on a lash-up of equipment that I can only smile at today.
There is certainly a place for automation. Those repeater contacts we have all made are aided by the rig's automatic offset shift on transmit. That makes sense, as it ties in with the band plan, repeater construction standards, physics of narrow bandwidth filtering, etc. We have no such structure on the transponder satellites, nor for a linear transponder do we really need one. In the future the communications channel will be much more complex in the services that it supplies, so yes, there will be automation there too. But for simple transponders, there is no need for complex handling techniques.
And, don't forget Engineer Scott's observation, or perhaps it was a warning: "The more they overthink the plumbing, the easier it is to stop up the drain."
Oscar-7 still works.
Greg KO6TH
Eric Fort wrote:
Yes, a zero hertz tone would be ideal if one were going to insert a tone for tracking. Not sure you’d need full carrier though. The advantage of a zero hertz tone is not having to notch it on rx, a ctcss tone is probably easier to generate on modern transceivers though. Having a (reduced) “carrier” to measure and track would seem to be an aid to automated tuning of the receiver though. Sound card listens for the tone and adjusts rx frequency according to the offset from a known and agreed upon transmit tone. What I’m hearing here in the comments though and I’ll ask if this is correct.... is that the computational approach of adjustment based upon published elements is good enough. Can and does the computer frequency control get us close enough for hands off operating when both stations us it?
Also if computer control and tracking is “good enough” why is it not almost universal on the transponder sats? For the cost of a Raspberry pi or similar sbc and the proper ci-v / cat cable you have computer control of frequency. As cheap as this is compared to the cost of an all mode radio why is it not more often put to use?
If computer control is not good enough for hands free operation, how can we make it so?
Af6ep
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On Apr 13, 2018, at 10:23 PM, Greg D [email protected] wrote:
"subaudible" is only sub audible when you're dead on frequency if you're using SSB. For FM, where we are familiar with the technique, that's fine. But instead of a tone, you'd perhaps be better off running Single Sideband AM (i.e. a sub audible tone of zero hertz); there was a satellite recently that was in that sort of mode (I forget which bird), and it was really interesting to work.
BUT, one huge problem with sending up a "beacon tone" for aligning stations to, is that you're sending a 100% duty cycle carrier (though perhaps reduced power) to a transponder that really hates having 100% carriers run through it. That's one of the big reasons why they don't allow FM on the SSB / CW birds (the other being the extra bandwidth that it takes).
Bottom line is that, yes, one can construct methods to aid in frequency tracking. But One True Rule software-assisted operation works really well already, for those who can use it, and can be backed all the way down to manual for those who can't. And, manual operation of an SSB station through a satellite is quite an interesting exercise. I often find it more satisfying than having to deal with starting up and fussing with all the computer automation "help". Just takes a bit of practice.
Greg KO6TH
Eric Fort wrote:
Computer control or actually a variation of such *IS* what I’m considering and proposing. Yes I have read “the one true way”. I understand this manual tweaking is how it’s currently done. Why however are we adjusting only one frequency? It seems that we can adjust the transmit frequency so that it is always the same distance from the beacon as seen by the satellite and the receiver can automatically track the subduable tone transmitted. This means that you need not drift across the transponder and the rx station automatically tracks. What am I missing in this being hands off and always on frequency?
AF6EP
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On Apr 13, 2018, at 7:49 PM, Andy [email protected] wrote:
So VERY true! Thanks Bruce, ANDY w5acm
-----Original Message----- From: AMSAT-BB [mailto:[email protected]] On Behalf Of Bruce Sent: Friday, April 13, 2018 9:40 PM To: [email protected] Subject: Re: [amsat-bb] Making the transponder sats as easy as the fm birds
Sorry, this theory of thought is incorrect. You must adjust the higher of the two frequencies as it is most affected by Doppler. The true way to adjust is really to adjust both frequencies, however in the absence of computer control of both frequencies, you adjust the higher. Thus, if it is the receive frequency, then you adjust the receive, if it is the transmit, then you adjust the transmit. Holding the transmit frequency on the wrong band will cause you to walk across all the other QSO's taking place which is not a good practice.
73...bruce
On 4/13/2018 8:41 PM, Eric Fort wrote: I’ve had an idea for a long time as to making the satellites with linear transponders as easy to use as the FM “easy sats “. Consider the following:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
Our tracking program gives us range to the satellite and its velocity relative to us given our location and the orbital parameters. From this we should have computed Doppler for both transmit and receive.
We also know the frequency at the satellite of the various beacons onboard. From this we can measure the doppler and work the other direction
If we transmit a subaudable tone of known frequency we should be able to adjust the rx automatically by tracking the tone. (Acssb)
Given these multiple ways of setting our tx/rx frequencies for our location can this not simply be automated to such a degree as to simply specify an offset from the beacon and operate as if it were a regular predictable opening on hf?
Af6ep
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On 2018-04-13 9:41 PM, Eric Fort wrote:
As I understand it, the goal is to adjust your transmitter such that your frequency at the satellite is constant.
I have been on the sats since Oscar 6 and the RS series and it was the other way around I thought. You kept the transmit steady and adjusted the receiver. I do not use computer control of the rig. I suspect my log has 400 entries.
Did the standard method change or have I been doing it wrong all these years
The general guidance in the early years of operating linear transponders was to adjust your transmitter to maintain a constant receive frequency. Experience with the Mode J transponder on FO-12 caused the gudiance to be updated to tuning the higher of the two frequencies. See the Sept 14, 1987 Amateur Satellite Report for more details ( http://www.ka9q.net/asr-1987.pdf).
With computer control, it’s a simple matter to adjust both your transmit and receive frequencies once you get your software calibrated, but for those tuning manually, the guidance is to tune the higher of the two frequencies and leave the lower frequency as constant as possible.
Operating linear transponders takes a bit of practice, but it’s fairly easy and becomes second nature after you get a dozen passes or so under your belt. There’s no need to think up new schemes to make them “easier.”
73,
Paul, N8HM
On Sat, Apr 14, 2018 at 08:19 Bill Booth [email protected] wrote:
On 2018-04-13 9:41 PM, Eric Fort wrote:
As I understand it, the goal is to adjust your transmitter such that
your frequency at the satellite is constant.
I have been on the sats since Oscar 6 and the RS series and it was the other way around I thought. You kept the transmit steady and adjusted the receiver. I do not use computer control of the rig. I suspect my log has 400 entries.
Did the standard method change or have I been doing it wrong all these years
-- Bill Booth VE3NXK Sundridge ON, Canada 79.23.37 W x 45.46.18 N FN05ns
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participants (9)
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Andy -
Bill Booth -
Bruce -
Eric Fort -
Eric Fort -
Gabriel Zeifman -
Greg D -
Paul Stoetzer -
Stephen van Jaarsveldt