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.