NVIS Antenna Addition
In early 2024 I joined North-Texas-NVIS-Net@groups.io. I had an old 80-10 ofc antenna with a shorted balun. I decided to disconnect the balun and use it as a nvis receive antenna.
I had plenty of room in a wooded natural area to stretch this antenna out at 6 feet off the ground.
This worked but I was getting a lot of rfi noise from solar invertors where the 100 ft coax from the antenna came into the shack.
Several years ago I had designed this amplifier to boost the signal from a MFJ Receive loop with a built-in preamp. I never got any satisfactory results from the loop, I decided to try the amp on my "New" NVIS antenna, and it works GREAT!
The Q1 J310 input FET is a very low noise VHF/UHF amplifier, and the 2SC5551A is a UHF large current driver. The output transformer provides matching to a 50 ohm coax, and extraction of the 12V coax supplied power. The circuit has flat 15 db gain from 100 KHz to 15 Mhz.
C1, C2 , L2, & L4 form an optional high pass filter to reduce overloads from nearby AM broadcast transmitters if needed, otherwise leave it disconnected.
J2 will provide 12 volts to the input coax if needed... George AF5LA
I designed the circuit board and had 20 made, so I have some spares if you are interested.
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