VO-52, Linear transponders and FM
Gang:
The conference for VO-52's second anniversary has on its agenda a discussion about design of a Hamsat2. This good news got me thinking about the innovative aspects of Hamsat: principal among these is that it has succeeded in using convention to determine the mode of operation. What I means by this is that, as I understand it, in regions of the world where SSB rigs might be in low supply, it is common practice, encouraged by the satellite's operators, to use its linear transponders to relay an FM signal. Here in N.A., and Europe, we use VO-52 nearly exclusively in CW/SSB.
I can't speak for the rest of the world, but I'd say that in this neck of the woods, this approach has worked very well. I've only once or twice heard an FM signal on VO-52, no more often than other birds, and rare enough that I can assume it was by accident or ignorance.
Given VO-52 success in this score, I wonder: a) if the operators of other, future, LEO linear birds should likewise permit their use in FM over appropriate regions of the globe. Since FM is such a high duty cycle mode, I suspect usage and battery load statistics from Hamsat might be helpful in guiding others' choices in this matter.
b) what advantage there is in launching a FM-only bird when a linear one can be used in both modes. I assume there must be reasons of efficiency, etc. since the designers of KiwiSat, for example, are making circuitry for both modes.
73, Bruce VE9QRP
At 03:40 AM 4/24/2007, Bruce Robertson wrote:
I can't speak for the rest of the world, but I'd say that in this neck of the woods, this approach has worked very well. I've only once or twice heard an FM signal on VO-52, no more often than other birds, and rare enough that I can assume it was by accident or ignorance.
I haven't checked this bird myself, because I lack 70cm SSB gear. Australia is in probably a more unusual situation. We have a relatively high penetration of VHF SSB gear, and a smaller, but significant amount of 70cm SSB radios out there. However, we also have a very low population density, compared to the US or Europe. I know when I was working RS-12/13, the only QSOs I had were those I had pre-arranged with local operators. It's much easier to find someone on FM. I believe there are some working Hamsat on SSB, from time to time, so it might be getting use here in SSB. I doubt there's much, if any FM activity on this bird, I think the convention for this part of the world is SSB.
Given VO-52 success in this score, I wonder: a) if the operators of other, future, LEO linear birds should likewise permit their use in FM over appropriate regions of the globe. Since FM is such a high duty cycle mode, I suspect usage and battery load statistics from Hamsat might be helpful in guiding others' choices in this matter.
Looks like there will be some useful lessons in here.
b) what advantage there is in launching a FM-only bird when a linear one can be used in both modes. I assume there must be reasons of efficiency, etc. since the designers of KiwiSat, for example, are making circuitry for both modes.
Indeed, though we would need to formalise arrangements a bit more then. For this part of the world, FM birds do serve a purpose, and that would need to be reflected in the local bandplan for any future linear satellites, if FM was going to be phased out. In other words, a CW/SSB/FM transponder bandplan in a 40-50 kHz bandwidth might be needed here. I'm sure a single FM QSO, 2 or 3 SSB QSOs and one or 2 in CW would happily coexist at the same time down here. Might also be room to experiment with managing the power sharing on a SDX as well.
Just thinking out loud...
73 de VK3JED http://vkradio.com
You could run digital modes that use the *SK modulation schemes. I'm unsure of how P25, D-Star, or any of the other modes would work inverted. Would have to actually test it out someday.
73 de Pat --- KA9SCF. Amsat #35741
b) what advantage there is in launching a FM-only bird when a linear one can be used in both modes. I assume there must be reasons of efficiency, etc. since the designers of KiwiSat, for example, are making circuitry for both modes.
73, Bruce VE9QRP
Hi All Been reading all your views on Hamsat. Mission management board informs us that Hamsat is in very good health and its one the sats that has drawn least attention with regard to house keeping. We have received many mails asking if FM can be used on Hamsat, though I am regular on SSB and CW mainly working some DX , while I do hear the qrm from FM sigs nearby. Only a couple of us have the SSB CW gear here and I agree that in most parts of the world SSB gear is scarce while FM radios are popular worldover. As in this region we want to promote Sat operation we have not discouraged some the beginners who want to try the satellite operation with their simple vhf / uhf handys. We have not enforced a strict NO to FM here as we want get them into the Sat working and slowly encourage them to move on to SSB / CW. We have recieved numerous mails from all over the world expressing their satisfaction and excitement of working the Hamsat as it is now one of the most easily workable LEO.
We have been having regular meetings with MMB and the Hamsat is in good health completing 2 years in a few days. News proposals have been planned for the Hamsat 2 and we welcome proposals from other sat operators , designers, amsat.orgs., etc sent to info@amsat.in
Thank you all for the support to Hamsat. Best 73 Pop VU2POP Secy Amsat India regd
participants (4)
-
Bruce Robertson -
Patrick Green -
Prathap Kumar -
Tony Langdon