On 2/1/2012 12:35 AM, James Moritz wrote:
I guess as far as LF frequencies are concerned, the Butternut antenna is
just a 10m vertical whip (provided you disconnect the coil across the feed
point - otherwise it will be nearly a short circuited whip...). This will
give you plenty of signal, provided the antenna is reasonably matched to the
RX input. Matching requires tuning it to resonance. The simplest form of
tuner is just an inductor connected between the feed point of the antenna
and the low impedance RX input
Jim and the group,
I used with good results the following schematic to match a
random piece of wire
to an LF Rx. Below also the Spice simulation. Gain is high, and
is given only by the
passive impedance step-up, so there are no risks of distortion, as
long as the Rx
does not saturate...
C1 is absolutely not critical, can range from 1nF to 4.7nF with no
practical changes
in the performance of the circuit.
73 Alberto I2PHD
![http://dl.dropbox.com/u/15089947/LFmatchSch.gif]()
![http://dl.dropbox.com/u/15089947/LFmatchGain.gif]()
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