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?

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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@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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