AM antenna. (proving yet again that a little knowledge can be a dangerous thing.)
I've been reading Terman's "Radio Engineer's Handbook" * on antenna's, and Charles Wenzel's web site,
My previous AM antenna was a ~10 foot piece of stranded wire (0.05" diam.) stuck into an inverting opamp. (Rin =1 kohm, gain =10, opa228, ) Today I made a non-inverting preamp out of a opa2134 and stuck the same piece of wire into it. (1 meg to ground for bias current) I got about a 3-4 dB increase in signal. I then tried adding some inductance right at the input. I strung three 100uH's in a row and clipped my antenna to the different taps.
Sang like the dickens, An RC, saw-toothie looking thing. about (~2.2 MHz to 1.7 MHz) More L leads to lower freq as expected.100k across the input didn't stop it, but 10k did. (10k the worlds favorite resistor?) What's going on? My antenna needs more current?
George H.*published 1943, first edition. There's a blurb in the preface about some things being left out because of the war.... it always makes me wonder as I read.