From FB group Building Transistor Radios, Jul 30
Hey, if you live in Central Florida, you really do need an optocoupler!
I got a Tennelec Memoryscan scanner on sale for a really cheap price back in the ’70s (the company quickly went out of business). I connected it to a VHF/UHF discone antenna on my roof. This had 3 elements only a few feet in diameter.
So a thunderstorm passed through and afterwards the VHF channels stopped working – UHF were ok.
Fortunately it came with a schematic. I immediately saw why. The VHF RF amp was directly connected to the antenna. No coil to give a DC path to ground. So I replaced the 2N3904 RF amp, and it started working again. So it’s a Big Mistake to connect a transistor, and especially a FET(!) to the antenna directly. Many good designs totally ignore this absolute no-no! And it happened to me with a tiny discone antenna. Imagine what happens with a hundred foot long wire!!
