[600MRG] re. Loop Antennas

[david vanhorn]

What sort of Q values were you able to achieve with the loop loaded to 50
ohms?

On Sun, Sep 8, 2024 at 5:01 PM Edward Larsen <ki6rcm98 at gmail.com> wrote:

>    Thanks Dave for the posting regarding loop antennas for VLF.  I like
> your approach and if your loop is out-performing a good active whip it is
> certainly working.
>    I did some loop tests a few years ago.  What I built was:
> 13 turns of silver plated AWG 22 stranded/teflon, 79" diameter, wires
> spaced 1/2" and crossed-over at the bottom (mobius wound).
>    About 725 uH inductance resonated to VLF with 80-1250pF varactor tuning
> capacitance.  Loop self resonance was about 3.02 MHz.  I used a one turn
> coupling loop inside which I adjusted for 50 Ohm match.  I've found that a
> high-Q tunable loop eliminates any overload or intermodulation problems in
> a receiver.
>    I left this loop with KI6MTV when I moved to Arizona.  I need to build
> another.  It would tune about 140 kHz to 650 kHz via vari-cap diode tuning.
>    I have designed/built a pretty good active amplified ferrite rod
> antenna for 17.2 kHz.  I can email you the schematic if you like.  It too
> parallel resonates the high-Q loop for sharp narrow-band tuning.  The
> circuit could be modified for higher frequencies if desired.
>    There has been a lot of excellent VLF loop design work in the past by
> several low frequency Gurus who published in the Lowdown magazine.
> Unfortunately this data is not available anywhere.  I have most of the old
> Lowdowns going back to the 1980s.
>    Keep on experimenting!
> 73
> Ed, KI6R
> SaddleBrooke, Az
>
>
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-- 
K1FZY (WA4TPW) SK  9/29/37-4/13/15
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