[amsat-bb] AO-92 fading

[Paul Andrews]

There are so many interesting "spin" mitigation experiments possible
with FM birds.

The FM constant level carrier makes signal strength plotting relatively easy.

1) A good tracking system and automatic doppler compensation are needed.

2) Two (2) downlink antennas.  One in V-pol and one in H-pol.

3) Data collection system.  Lot's of options here.   Sample rate
should be at least 10 samples per second.

Questions:

- Would every pass have a different spin profile?

- Is spin a bigger problem on low elevation passes or high elevation passes?

- How deep are the nulls?

- Are V-pol and H-pol nulls synchronized?   Do V-pol and H-pol nulls
occur simultaneously?

- Compare AO-92 spin to an NOAA weather satellite (which is
stabilized).   NOAA Sat might be a good baseline plot.

- Perform the same test with a single Circular Polarized antenna.
What are the results compared to V-pol and H-pol?

-----------------------

This would make for a great paper to be presented at an AMSAT Conference.

73 - Paul - W2HRO


















On Wed, Mar 28, 2018 at 11:45 AM, Roy Dean <royldean at gmail.com> wrote:
> If you have separate uplink and downlink antennas, both with independently
> switched polarity, couldn't you tune the polarity on the downlink to best
> reception, and then transmit while listening and simultaneously flipping
> polarity on the uplink?  You'd have to switch a couple of times quickly to
> be sure you weren't experiencing a downlink fade.   Just a thought.
>
> -Roy
> K3RLD
>
> Again, even in full duplex how do you distinguish between a
>> non-matchinguplink vs non-matching downlink? You only "hear" the downlink!
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