Bill tweaks his AM loop antenna for optimal mediumwave performance
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 loopWith 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!