Hello LFers,
A combination of time off and good weather finally let me try out the
series tuned into a transformer hookup on my loop. After trying out
several ratios, I found that 4:1 seemed to produce the best signal at
the receiver. That was achieved with 20 turns on the feedline side
and 5 turns on the loop side, wound on a toroid from a computer
power supply. Using my portable LF receiver tuned to the loop's
frequency and sitting closeby, I noted no drop in the signal strength
when I connected up the feedline using the transformer approach.
I can tune up or down from the loops tuning setting about 25 kHz.
before the signals drop off a bit, so I'm thinking the Q of the loop
isn't getting spoiled like it had been by the shielded pickup, which
I've left in place but disconnected.
On another note, I connected a decade resistor box to the shielded
pickup loop pigtail and found that I could go down to around 4700
ohms before I noticed that it started to load down the main loop.
I'm going to try hooking a HI-Z input preamp to the pickup loop
and see how that compares to the transformer hookup. I placed
the parts order today for the preamp shown on page 19 of the
Low Frequency Experimenter's Handbook.
I want to thank all of you who have helped me through the problem
with my big loop, especially to John, W1TAG, and Jim, M0BMU,
who had suggested using the series tuned transformer feed method.
73, J.B.
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