[amsat-bb] AO-92 fading

Wed Mar 28 01:54:09 UTC 2018

Hi Sterling,

That would assume you have the ability to switch between linear uplink
polarization (vertical and horizontal) and circular polarisation for uplink
(right and left) and keep you downlink polarization on the same
optimized path all the time, meaning you know in advance which way the
downlink signal is the best to compensate for any uplink discrepancies.
Good luck :-)

But hanks, good thought!

Stefan, VE4NSA

On Tue, Mar 27, 2018 at 8:47 PM, Sterling Coffey <kawfey at gmail.com> wrote:

> 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)
>>>> > > >
>>>> > > >
>>>> > > > _______________________________________________
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>>>> > _______________________________________________
>>>> > 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.
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>>>> >
>>>> _______________________________________________
>>>> 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
>>>>
>>>
>>>
>>
>