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

David Swanson dave at druidnetworks.com
Tue Oct 17 04:03:06 UTC 2017

On the FO29 pass at 0155z this evening, I noticed a very hard time getting
into the transponder. The pass was nearly overhead, and the 3w-4w that is
normally sufficient was barely cutting it. I also noticed it was 'up and
down' alot, whereas some moments it was easy to get in, then it would be
nearly impossible. There were also pockets of 'noise' all over the
transponder, that sounded somewhat digital, but I just couldn't place them.
I found W5PFG in the passband (who was portable in a rare grid in western
Texas) and he commented on the difficulty of working an otherwise easier
bird tonight as well. I checked the screen, and no other birds were
obviously in range, so I started scanning around the passband to see what I
could hear. Up around 435.870 I found (or rather heard) what I was looking
for. I fired up my recorder and captured this:


For those not familiar, that is the telltale sound of MSK144. I work a fair
amount of Meteor Scatter in addition to operating satellites, and the noise
is unmistakable. Since my shack PC has wsjt-x installed, I quickly fired it
up and went to the msk144 mode and after some quick tweaking started
decoding the signal. This is a screenshot of what I saw:


This signal continued for at least 8 minutes (that I recorded) in a 5
second T/R cycle while FO29 was passing high over North America. Every 5
second the digital signal would get transmitted, and all other SSB qsos
would start to fail. You might call this an experiment, but I call it
intentional QRM.

*For the record* You are not the first person to play with wsjt-x modes on
the linear satellites. Some months ago during the late night hours on the
XW's and FO29 when the footprint was primarily over the desert southwest
and south pacific, I to "experimented" with FT8 and MSK144. I purposely ran
my transmitted signal thru over 100ft of low grade coax to attenuate my
uplink to ~1.5w ERP. I made sure the entire transponder was empty before
starting, announcing myself, then started the transmission. I decoded
myself successfully, said "Well that was dumb" and never did it again. I
purposely didn't announce what I had done to the world because I knew
someone would think they were being cool too, and would fire up a 2700hz
wide 50% duty cycle mode on a high US pass and QRM people trying to make
QSOs out of existence, because said individual would lack even basic
situational awareness and courtesy to others. What is extra hilarious about
the fact that it is you being the responsible party for destroying a pass,
is your constant whining to this mailing list about people using too much
power on AO-7, when you're one of the worst offenders. On July 16th this
summer, I was roving in EM35 and you called me on the 2155z pass of AO7,
and you got the first 3 letters of your callsign out before you killed the
bird. I know it was you, because I had already made 3 QSOs right at my AOS
with other stations using a reasonable amount of power, and as soon as you
key'd up the whole bird started FMing and croaked before you even finished
your call. You didn't get that grid that day, and after the stunt you
pulled this evening - you won't be getting any grids from me in the future

-Dave, KG5CCI

On Sat, Oct 14, 2017 at 2:24 PM, Ronald G. Parsons <w5rkn at w5rkn.com> wrote:

> Dave,
> 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.
> Ron W5RKN
> On Oct 14 14:34:56 UTC 2017, "Dave Webb KB1PVH" <kb1pvh at gmail.com>
> wrote:
> >Ron,
> >
> > 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.
> >
> >Dave-KB1PVH
> >
> >
> >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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