Short Takes #28: Mastering the Waves -- A Primer on the Mag Loop Antenna

After reading this article, I was motivated to take my Alexloop out for a POTA activation. I set it up with my Icom 705 running 5 watts CW. My first contact was F4WBN and my hopes were up. 54 minutes later, I had 11 contacts, including Sweden and Belgium. Here’s the QSO map:

 

I used an alexloop indoors on a speaker stand in 2017 and 2022 QRP with digital modes (JT65 RIP) for about 1000 QSOs. I worked QRP WAS and verified about 40 different countries on LOTW. I'm going to set it up again and work FTx modes and CW with a straight key over the winter.

Really fun.

 

ps thanks for the link the article - I enjoyed it.

 

Our Guest Author did a great job! Thanks for feedback. Dave, W7DGJ

 

Has anyone else done a reception test with a Mag Loop? For transmit a tiny coil or a 100w light bulb on the end of the coax will get out fine because mag waves are mag waves. I have a 17' tall vertical beside the house and a A3S on the roof. I tested them against a mag loop and found transmit wise the mag loop was a good match. But when it came to receiving it was 10db or so below the vertical and the beam. probably because a smaller antenna is cut by fewer Magnetic lines.

 

I have not seen any reception tests specifically for mag loop antennas. However, some calculators can provide some predicted performance based on the antenna's parameters. Results are mainly transmission related, but there are some which can help with understanding reception: efficiency, bandwidth, tuning capacity, capacitor voltage, resonance current, radiation resistance, loss resistance, inductance, inductive reactance, and quality factor. Also keep in mind the directivity. Rotating the antenna may improve or degrade reception. Mag loops certainly present compromises to higher gain antennas and other directional antennas. And polarization may also be a factor.