[amsat-bb] AO-92 fading

Wed Mar 28 01:47:11 UTC 2018

If linear polarized, if you can keep your RX/downlink antenna still and you
can at least hear the satellite, and rotating your TX/uplink antenna
results in correlated signal level changes on the RX/downlink, then you've
isolated it to the uplink polarization variable.

On Tue, Mar 27, 2018 at 8:44 PM, Stefan Wagener <wageners at gmail.com> wrote:

> Thanks,
>
> Again, even in full duplex how do you distinguish between a non-matching
> uplink vs non-matching downlink? You only "hear" the downlink!
>
> 73, Stefan VE4NSA
>
> On Tue, Mar 27, 2018 at 8:38 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)
>>> > > >
>>> > > >
>>> > > > _______________________________________________
>>> > > > Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum
>>> available
>>> > > > 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.
>>> > > > Not an AMSAT-NA member? Join now to support the amateur satellite
>>> > > program!
>>> > > > Subscription settings: http://www.amsat.org/mailman/l
>>> istinfo/amsat-bb
>>> > > _______________________________________________
>>> > > Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum
>>> available
>>> > > 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.
>>> > > Not an AMSAT-NA member? Join now to support the amateur satellite
>>> > program!
>>> > > Subscription settings: http://www.amsat.org/mailman/l
>>> istinfo/amsat-bb
>>> > >
>>> > _______________________________________________
>>> > Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
>>> > 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.
>>> > Not an AMSAT-NA member? Join now to support the amateur satellite
>>> program!
>>> > Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>>> >
>>> _______________________________________________
>>> Sent via AMSAT-BB at amsat.org. AMSAT-NA makes this open forum available
>>> 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.
>>> Not an AMSAT-NA member? Join now to support the amateur satellite
>>> program!
>>> Subscription settings: http://www.amsat.org/mailman/listinfo/amsat-bb
>>>
>>
>>
>