70 cm Preamp Follies

Last weekend Al KB2AYU and I (Al really did the work) put a Mirage 70 cm preamp up on the satellite antenna tree. Once installed we tested it and found that it made no difference in the received signal. So I had another identical preamp that I had tested and found working, so we swapped it out tonight - and found the same result. We had the control box that provides 12v to the preamp connected between the antenna switch and the antenna, and in that position it didn't work. So I decided to move it to the radio side of the switch and installed it with the control box input coming from the SDR radio and the antenna side of the box connected to the switch (the switch selects either the SDR radio or the 847 to be connected to the antenna). Strangely, this configuration worked! The noise level jumped about 20 db when the preamp was powered up, and a NO-84 PSK pass showed a much clearer signal on the downlink. Neither of us could explain why this configuration worked and the previous one didn't - the only difference was the position of the antenna switch along the line. So if you visit the clubhouse and see this configuration, don't change it!

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