HAM RADIO - Magnetic Loop Antenna 20m-40m

Thank you for this video--great documentation of the mag-loop. Really considering going down this rabbit hole--you're reigniting my curiosity in antenna. Keep on with the awesome work (with all you videos)!!

The vageries of magnetic loop antennas take a lot of learning . They are very effective in conditions where normal antennas struggle due to noise and poor propogation and the directionality of their gain means that you can pull signals out where none seem to be. I love mine ,especially for QRP , and have had some very surprising results . Keep at it - you will learn to love it as you get to know it better. (I now adjust mine instantly entirely by ear !). It's a bit like learning a musical instrument. 73 M7BLC

Nice project antenna. You may want to consider putting a 1:1 balun line insulation in the feed line coax at the antenna. MLAs are prone to common mode currents which will limit the amount of power you can apply to the antenna and limit the ability to get a good low swr. MLAs have very low radiation resistance so there can be 15 amps on the loop say at 30 watts plus thousands of volts on the capacitor. Soldering the loop to the capacitor will greatly improve efficiency and reduce mechanical resistance losses which is the biggest problem in loop design. I really like your project antenna. Great job and well engineered! Best 73s. Dan K1YPB - On the air since 1962

I have quite a lot of experience with magnetic loops. You can see the two loops I have in regular service on my QRZ page. MFJ made a loop tuning box that was rated for 100+ watts. I have used one to make portable field antennas on many occasions with excellent results. It must be kept in mind that high voltages can develop across the capacitor. It is essential that you insulate the cap from the tuning knob or tuning motor particularly if you are tuning under power even a few watts. Ohmic resistances are a critical source of efficiency loss. You might do better by soldering a copper washer to the copper tubing. Alternatively, just using a screw with a large head and the smallest possible hole to connect the capacitor might be helpful. you can purchase a venier drive used to help with the small increments that tuning requires. It is generally recommended that you use a BUTTERFLY capacitor or a vacuum variable capacitor. Otherwise you will suffer ohmic losses at the wiper contacts. The effects of a very small angular change on the peak frequency is remarkable. With air variables you wiould have to use a reversible DC motor with gear reduction or even a stepper motor with gear reducion for romote tuning. My vaccum variable loop tunes remotely using a homebrew PWM motor control and a NanoVNA. Magnetic loops are surprisingly sensitive to ambient conditions; temperature changes and/or humidity changes will shift the position of the peak.

Great information. I was thinking about a monoband loop antenna for 20m CW portion. Would it work with smaller capacitor or a RG213 as a capcitor? Is there a way to find how much capaticance is needed?

Nice MagLoop Almir, good Job on that. The capacitor should be on top and the small loop on the bottom. This reduces the receiver noise.Or Am I mistaken? Happy Weekend & 73 de Uncle Günter from across the Pond 💯🙋‍♂