KA6U Update - 902 EME Station Ready to Run - 2200UTC August 19, 2023

I have finished installing and testing the 902EME station in the roving vehicle.

This weekend I completed 5 QSOs on 902 with W5LUA, W5AFY, VE6TA, VE4MA and K5DOG.

First time I turned the station on completed QSO with Al W5LUA!

The station has switchable H/V polarization and I am running 200W at the feed.

RX performance is excellent.  On TX I had some problems being heard running 200W.  I shortened the TX feedline to 12ft of LMR600, removed the wattmeter and a jumper cable and I was heard better.

The smallest station I have worked so far is a 3M dish running 300W.  I still need to test with 2.4M dishes.

902 degradation today was -2.4 and for my upcoming trip it will be below -.6 because the Moon will be at perigee.  This should help.

Hopefully by the end of 2023 I will increase TX power by 4db to 500W at the feed if required.

This was my first significant operation on 902.  There was deep and rapid fading of signals and I did experience a 90 degree rotation of signals during the operations.  I characterize the band behavior today as as similar to 222Mhz.  I was running linear polarization.

We did a lot of testing with polarization switching and were careful to only have one station change polarization at a time to avoid "chasing our tail" with both stations switching and missing.  There were a couple of tests where rotating the feed 45 degrees made a difference.

There is talk of going to CP on 902.  I'm not sure that is a good idea at this time.  The folding dish on 902 seems (from the small data sample so far) to be several db less affective than on 23cm.  This is expected because of the smaller dish size to wavelength -> less gain.  There may not be enough RX margin on 902 to account for the -3 db impact of CP and the loss in the hybrid combiners used with patch feeds.

CP would be great for the "big" stations, we need to see for the 2.4M folding dishes.  I attribute the excellent RX performance on 902 to linear polarization and no hybrid combiner to create circular polarization.  Again we will need to test this over time.

Here are photos of the 902 station setup:

902 patch feed with H/V relay, TX/RX relay, preamp, and isolation relay on W2HRO dish

Paul supplied extra stiff mounting pole for feed and electronics, very little sag

ICOM 705 with polarity switching toggle switch 144Mhz IF with Q5 transverter

ICOM 705 only running 1.5W output to transverter - no cooling required

Laptop with extension screen WSJTX2.6 PSTrotator, Sectravue

Q5 Transverter, amplifier keying isolation box, external sequencer

250W Motorola PA, 28vdc power supply, 2 12V brushless cooling fans

12 foot LMR 600 feedline to dish directly behind car

20 amps from supply delivers 250W from PA and 200 at the feed