Loop antenna question.

[loopstick]

Originally Posted by jr_tech

I used a varactor tuner similar to the one shown in this article:
http://www.randombio.com/loopantenna.html
With 1Meg resistors, I picked up "hum" on some stations, likely due to nearby power lines in my area. If I lowered the resistance enough to eliminate the "hum", the tuning of the antenna became very broad (low Q)... so I installed the manual tune box, seen above the rotor.

jr

Maybe it was the lower Q that made the 60 Hz wiggle in the voltage controlled capacitance less noticeable. IOW the 60 Hz variation in capacitance was still moving the loop back and forth across its peak but because the peak was softer you couldn't really hear this happening. Another theory is that lower resistance = lower RFI susceptibility.

Even though I don't have a remote loop I'll still on occasion use a portable (RF-2200, ATS-803A) to peak the loop because the receiver / tuner lacks a signal strength meter and the AGC masks audible peaks. When I first got into this stuff I thought everything had to be up on the roof or in the attic or on some high mast. But that's not the case with AM. Anyhow good work.