[amsat-bb] Re: VO-52, Linear transponders and FM
vk3jed at gmail.com
Mon Apr 23 16:04:39 PDT 2007
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
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
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