Bill tweaks his AM loop antenna for optimal mediumwave performance posted on SWLing

Many thanks to SWLing Post contributor, Bill Hemphill (WD9EQD), who writes with the following update to his previous post:

As you may remember, back in May, I picked up a beautiful home-made loop antenna. It was 25 inches on a side with 23 turns of wire. My initial testing showed that it would tune from 280 kHz to 880 kHz. While I was familiar with loop antennas, I had never tried using one.

My initial tests were disappointing. So I spent some time on the internet reviewing AM loop antenna designs. I came across a reference to an AM Loop Antenna Calculator by Bruce Carter:

http://www.earmark.net/gesr/loop/umr_emc_calc.htm

I first measured the tuning capacitor and found that it tuned from 25 to 400 pF. Entering the data into the calculator:

This matches closely to what I was experiencing.

I then proceeded to calculate various Number of Turns to see the effect on tuning range. My goal was to tune the entire AM broadcast band.

I settled on ten turns which gives the following from the calculator:

Perfect. I removed 13 turns (which left ten turns) and then added a two turn secondary loop which would be connected to the radio. The results were fantastic.

I have created three short videos showing the difference between using the Tecsun S-8800 without the loop on a weak station and then using it with the loop.

[Note: If you’re viewing this post via our email newsletter you might need to view this post via a web browser to see the following embedded videos.]

Without the loop

With Loop

As you can hear, a very noticeable difference.

[After making these videos] I tested the of reception of 1510 kHz on the Panasonic RF-2200:

The results are amazing.

I have logged three stations on one frequency. Just peak the one station, then tune the loop and peak the second, then turn the loop some more and peak a third station.

I’m having a lot of fun with the loop. When it gets a little cooler, I plan to take it to the park where there is zero noise and really put it through its paces.

Excellent job, Bill! You’ve proven that doing a little research and making small adjustments to an antenna design can yield impressive results! Thank you for sharing!