[amsat-bb] AO-92 fading

Wed Mar 28 01:46:36 UTC 2018

The telemetry nuts should have some idea.  Independent of any uplink.  Good
SDR recording exercise and study.

Mark N8MH

On Tue, Mar 27, 2018 at 9:41 PM Sterling Coffey <kawfey at gmail.com> wrote:

> You can hear your own signal if you have a full duplex (two radio) setup.
> However, it's still pretty hard to tell if you use a single antenna (arrow,
> elk, etc) since you're changing the RX polarity while you're changing the
> TX polarity too.
>
> On Tue, Mar 27, 2018 at 7:22 PM, Stefan Wagener <wageners at gmail.com>
> wrote:
>
> > One of the questions I have is why one would think that the uplink
> > (polarization) is a problem since you only have the downlink to assess
> and
> > how would you differentiate between uplink "weakness" from downlink since
> > that is the only thing you hear. In addition, at least for uplink, you
> > could "in principle" very quickly adjust with higher power... and no, I
> am
> > NOT promoting crocodile behavior (big mouth little ears)
> >
> > Stefan, VE4NSA
> >
> > On Tue, Mar 27, 2018 at 2:26 PM, Burns Fisher <burns at fisher.cc> wrote:
> >
> > > If you have seen a model or picture of the Fox satellites, you may have
> > > noticed that some of the solar panels seem to be mounted off-center.
> > This
> > > is intentional so that photons that reflect off the shiny side give it
> a
> > > tiny off-center push that spins the bird to distribute the heat more
> > > evenly.  Thus it spins faster the more time it spends in the sun.  In
> > > addition, when it crosses the equator, it should flip over (-Z and +Z
> > > reverse sides).  This is because of the passive magnetic stabilization.
> > > But I'm guessing that since it is spinning, that causes it to wobble.
> > >
> > > Why 92 seems worse I don't know--I can only assume it has something to
> do
> > > with the orbit.  That graph that Paul posted looks very different from
> > > AO-85, for example.
> > >
> > > Some RF person can correct me, but I believe that the 70cm antenna only
> > > uses the antenna that sticks out one side, while the 2m antenna
> actually
> > > uses the antennas on both sides.  Could that explain why the uplink has
> > > more fading than the downlink?  I don't know.  Something to think
> about.
> > >
> > > 73,
> > >
> > > Burns WB1FJ
> > > Fox-1 Flight Software
> > >
> > > On Tue, Mar 27, 2018 at 2:12 PM, Paul Stoetzer <n8hm at arrl.net> wrote:
> > >
> > > > All of the Fox-1 satellites seem to spin faster or slower depending
> on
> > > > orbit illumination or other factors.
> > > >
> > > > For example, this is the +Z panel rotation on AO-92 since launch.
> > > >
> > > > https://imgur.com/a/uS8TB
> > > >
> > > > Someone more well-versed in these matters can comment further on what
> > > > causes this, but it is definitely not an indication of the health
> > > > status of the satellite.
> > > >
> > > > 73,
> > > >
> > > > Paul, N8HM
> > > >
> > > > On Tue, Mar 27, 2018 at 1:59 PM, Jean Marc Momple
> > > > <jean.marc.momple at gmail.com> wrote:
> > > > > Dear All,
> > > > >
> > > > > I have been experimenting with AO-92 as from its launch. Some
> > > > observations:
> > > > >
> > > > > 1) The fading on this bird seems to be high and quite
> unpredictable,
> > > > requires a lot of changes of polarization  to keep the Rx signal to
> an
> > > > adequate level.
> > > > >
> > > > > 2) Seems that the fading is both on the U/V and L-mode, more seems
> to
> > > me
> > > > that the uplink is more affected.
> > > > >
> > > > > 3) Telemetry seems to be quite reliable with FoxTelem in all modes.
> > > > >
> > > > > Today, it was even worse losing the bird many times during the
> pass,
> > it
> > > > seems that it is degrading quite quickly, hope that this is not the
> > case.
> > > > >
> > > > > Just to share my observation.
> > > > >
> > > > > 73
> > > > >
> > > > >
> > > > > Jean Marc (3B8du)
> > > > >
> > > > >
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> _______________________________________________
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> 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.
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-- 
Mark L. Hammond [N8MH]