Cutting-edge diy projects
Achieved today something that I’ve wanted to do since I was a teenager: bounce a signal off the Moon. I was able to achieve that today for the first time!
Echoes were faint, but readable. Next, maximize power transfer to antenna and increase power to 600W.
This weekend I exchanged the LNA isolation relay by a transmit-type relay with N connectors, and replaced a short cable and N-to-SMA adapters by just two N adapters. This gave me one extra dB of Sun vs. cold sky. I then swept the position of the feed very carefully, but the best I could get was 9 dB of Sun noise.
KC2TDS (Jason) and I calculated the F/D of the dish to be around 0.45, which would mean that the septum feed would be OK as-is, but the dish’s manufacturer specs state its F/D at 0.37, although with inconsistent measurements. I decided to try a scalar ring to change the feed’s beam pattern in case that would be the reason for my low Sun measurements.
I cut out an 18″ diameter x 3″ deep “Fat Daddio” cake pan to allow the feed to protrude through the center. I reinforced the two sides of the orifice with frames cut of the waterjet. Two brackets hold the scalar ring firmly against the feed.
I am limited by the geometry of the struts, but was nevertheless able to gain 2 dB of Sun noise vs. cold sky (for a total of 11 dB) with this arrangement! ON0EME now comes in at approximately 5 dB above my noise floor, making for easy copy.
I also wired the TX port all the way to the nearby shed where the PA will reside, but didn’t get to wire the RX/TX relays, so trying to transmit and receive echoes off the Moon will have to wait until next weekend.
Sun Noise vs Cold Sky, and ON0EME copy with N2QG’s 12 ft dish
12 ft dish at N2QG with 1296 MHz septum feed and scalar ring.
After two weeks of battling with my receiver setup, I finally found the problem: The output stage of my home-brewed GPS-disciplined 10MHz reference was clipping on one side, which caused the AOR AR5000 to misbehave. My reception cleaned up as soon as I connected the rubidium reference instead of the GPS-locked source.
The feed is not optimized because I’m receiving only 8dB of Sun noise above cold sky, but this was nevertheless good enough to receive and clearly copy by ear the ON0EME beacon bouncing off the Moon.
Next: Optimize the feed and connect the power amplifier to start transmitting my own signals towards the Moon.
RS0ISS transmitted PD120 SSTV postcards December 28 2019 – January 1 2020 in memory of cosmonaut Alexei Leonov. I received the signals at 145.800 MHz using my new IC9700 rig and a M2 2MCP8A antenna. I did not use Doppler compensation, which accounts for some of the wobbliness. I used Nova for Windows to track the ISS.
Air Force Major General Alexei Leonov (1934 – 2019) was a Soviet and Russian cosmonaut, who in March 1965 became the first human to conduct a spacewalk. In July 1975, Leonov commanded the Soyuz capsule in the Soyuz–Apollo mission.
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