Stefan,

My observations, not backed by science or a good understanding of antenna theory, is that the polarity peaks (best reception) are fairly broad, while the nulls are pretty sharp. (I studied electrical engineering, but I was never good at field theory.)

As a result, I can twist the Arrow a little off of the best reception point without taking too much of a received signal strength hit, while allowing me to move the transmit polarity away from a null. At least that is what seems happen when I’m operating portable.

73, Steve N9IP -- Steve Belter, seb@wintek.com

From: Stefan Wagener wageners@gmail.com Date: Tuesday, March 27, 2018 at 10:39 PM To: "Stephen E. Belter" seb@wintek.com Cc: Sterling Coffey kawfey@gmail.com, Paul Stoetzer n8hm@arrl.net, AMSAT-BB amsat-bb@amsat.org, Burns Fisher burns@fisher.cc Subject: Re: [amsat-bb] AO-92 fading

Thanks Steve,

Great point and well thought out. Now, let me ask you a question: After you matched the downlink signal and position of your Arrow for maximum quieting and best signal, what happens when you now change the position of your arrow to look for best "uplink"? unless yo can keep the downlink position steady you will not be able to check for the uplink.. as science tells me one thing has to be constant for the other to be assessed...

All the best,

Stefan, VE4NSA

On Tue, Mar 27, 2018 at 9:27 PM, Stephen E. Belter <seb@wintek.commailto:seb@wintek.com> wrote: Stefan,

You are correct that you only hear the downlink, but...

From personal experience, including operating AO-85 and AO-91 today using a standard Arrow and an IC-821 (from a campground in EM87), I'm convinced that I can hear my uplink polarity mismatch.

I first adjust the polarity of my antenna (by twisting my wrist) while searching for the strongest (maximum quieting) received signal. Then while pressing the PTT, I tweak the Arrow polarity while going for maximum quieting while listening to myself.

The best sounding full-duplex signal is typically not at the same polarity as the best received signal from someone else on the satellite, but I've been able to get full quieting full-duplex. When operating full-duplex, I think I'm hearing the results of *both* the uplink and downlink polarity match.

And that's how I 'differentiate between uplink "weakness" from downlink' weakness.

73, Steve N9IP -- Steve Belter, seb@wintek.commailto:seb@wintek.com

On 3/27/18, 10:06 PM, "AMSAT-BB on behalf of Stefan Wagener" <amsat-bb-bounces@amsat.orgmailto:amsat-bb-bounces@amsat.org on behalf of wageners@gmail.commailto:wageners@gmail.com> wrote:

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@gmail.commailto:kawfey@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@gmail.commailto:wageners@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@gmail.commailto:kawfey@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@gmail.commailto:wageners@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@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@arrl.netmailto:n8hm@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@gmail.commailto:jean.marc.momple@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@amsat.orgmailto:AMSAT-BB@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@amsat.orgmailto:AMSAT-BB@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@amsat.orgmailto:AMSAT-BB@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@amsat.orgmailto:AMSAT-BB@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@amsat.orgmailto:AMSAT-BB@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