[Lowfer] Loop Practice ?

[John Andrews]

Peter, Bill,

OK, here are the results. I used an aero beacon about 5 miles away on 
417 kHz, and the readings were taken about 1.5 hours before sunset, so 
the signal was stable. The nearby big loop was shorted and grounded, so 
there would be no unusual tuning effects.

The null when using all 14 turns was about 21 dB, but it dropped to 17 
dB when only 7 turns were used. So...on the face of it, Bill may have a 
point. The presence of the grounded conductor for the 480' perimeter 
xmit loop being only 10 feet away sets up some possibilities for 
electrostatic coupling. The nulls seemed symmetrical, when the loop was 
rotated 180 degrees, to the best of my ability to measure. Since I don't 
have a rotator on the thing, this required some back and forth trips 
from the house, and the use of wireless headphones to hear the null.

The balance of the loop otherwise should be pretty good, as it is series 
tuned into a winding on a toroid.

JA

John Andrews wrote:
> Peter, Bill,
> 
> I have a 7-turn tap on my 14-turn loop (6' square), and have used it 
> before with no strange results. But Bill makes a very good point. If the 
> time and weather permit tonight, I'll try to measure the depth of a null 
> both ways. Will probably have to do it with an aero beacon down in the 
> 200-300 kHz range. Stay tuned...