I have used the MFJ model (1786 ?) which covers 10 to 30 MHZ.
I have also used various horizontal "wire" loops in bedrooms & currently have a 40M full size version
(more-or-less) following the edges of my loft - about 33 ft AGL. This one is a good general-purpose qwiet receive antenna for 80 upwards, a reasonable NVIS in the day, all-round EU by night on 40M and "OK" generally on higher bands.
I feed it at a corner with 100 Ohm coax into a T type tuner - not purist but OK. So I guess this is similar in
polarization & effect to Wayne's indoor loop.
The MFJ is mounted high in the same loft in its' vertical orientation. Results over a no. of years have generally been better than the expectation for a "small" antenna - eg 1st contact on 10MHZ when newly-installed was a cross-town CW chat - but - followed immediately by Reunion Isle and then a ZS before the EU pile-up wiped-out my QRP !
Understand some of the MFJ quality comments - but this loop is manufactured like a tank - including the butterfly C. The weak part of the system is the tuner - the cross-needle bit was hard to interpret & has now failed -
however, I have added an-inline VSWR/Power meter & it seems as good, with the bonus that I need << 15 W MFJ recommend when tuning...
There is a big long-running debate between Jack Belrose & Mike Underhill re the efficiency/performance of small
loops - well worth trying to follow (I'm at work, call-signs not to hand - I can supply some refs if wanted)
The other bonus is - it acts as useful pre-selection, although not required for the K2 !
I am trying to figure out how to couple a low-loss inductor effect into my loop to get it down onto 40M -
I suspect MFJ use a different, bigger butterfly capacitor in their 40M version. Any comment on my problem would be appreciated
72
George G4TPV
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