[amsat-bb] WSJT-X FT8 QSO confirmed between W2JAZ and W5RKN on FO-29

Ronald G. Parsons w5rkn at w5rkn.com
Sat Oct 14 19:24:16 UTC 2017


I some sense you are right, but this is a weak signal mode usable only when the satellite is far away so the Doppler shift change each second is very small.  It isn’t the power being transmitted, but the power received at the satellite that matters, and it was being used only when the satellite was near maximum range. There were other signals on the transponder, both SSB and CW, that were so strong they were causing both amplitude changes and “FMing” of my downlink signal. During preliminary testing with the satellite near, I observed no noticeable changes to other signals in the passband when my signal was strong. Strong CW and SSB signals from others, due to their amplitude changes did produce noticeable changes to my downlink. This could be why we were not successful on AO-7, but were successful on our first try on FO-29, which is more tolerant of other strong signals on the passband.


On Oct 14 14:34:56 UTC 2017, "Dave Webb KB1PVH" <kb1pvh at gmail.com> wrote:

> I feel your email is a little like "Do as I say, not as I do". Aren't you
>posting repeatedly asking people to use low power on AO-7, and here you are
>attempting a full duty cycle mode on AO-7.
>Sent from my Galaxy S7

On Oct 13, 2017 11:18 PM, "Ronald G. Parsons" <w5rkn at w5rkn.com> wrote:

> A few days ago, Rick, W2JAZ, asked me if the new, short, weak signal
> protocol, FT8, could be used on satellites. I posited it might work near
> AOS or LOS where the Doppler corrections are small. FT8 is operationally
> similar to the older protocols but four times faster (15-second T/R
> sequences) and less sensitive by a few dB.
> So we set out to configure our satellite stations to use WSJT-X with FT8.
> With some configuration advice from W0DHB, we each got our systems
> configured. Mine (W5RKN) is a Flex-6500 with two DEMI transverters running
> SmartSDR, SatPC32, FlexSATPC, and WSJT-X. Rick’s (W2JAZ) is a Flex-5000
> with U/V module, running PowerSDR, SatPC32, FlexSATPC, and WSJT-X.
> After a couple runs on AO-7 without success, we tried again tonight on the
> 0220Z (14 Oct) pass of FO-29. I started out at my AOS calling CQ W5RKN
> EM10. After several transmissions without success, the reply W5RKN W2JAZ
> FN29 popped up on the screen. Then followed the usual signal report, RRR
> and 73 transmissions.
> As soon as I can figure out the appropriate fields for LoTW, we’ll log the
> QSO there.
> I am not aware of other WSJT-X QSOs on the satellites, so I’d be
> interested in other’s experiences,
> Ron and Rick

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