Thursday, September 23, 2021

Magnetic Loop Antenna - my practical mods so far

 As written before building and experimenting a MLA is very addictive. You can always improve things and learn a lot from it. First of all I have to tell that my MLA is designed for indoor use, I consider it too weak for the outside and tuner box is not watertight. Although I can always put the box into a plastic bag or something.

First of all I had issues with the coupling loop. It was soldered directly to the PL259 chassis (or is it a SO239 chassis?). The soldering broke many times when experimenting so I decided to copy kind of OM0ET's idea, although I'm not that gifted. Practically it works well... I also decided to keep the length of the coupling loop 72cm, smaller as I had before. 

Another thing I would like is a possebility to mount the MLA on a tripod. My tuning box was designed to put it on a table of some sort. But if not available I had to put it on the ground which causes too much losses. How to solve this challenge since the thread on the tripod is 1/4" UNC. Something not really common in the Netherlands and hard to find a tap for it. But since I have a job in repairs we have some UNC/UNF bolts and nuts in stock. I found a suitable nut. The thing I did is drilling a hole in an iron strip big enough to fit the nut in and weld it to the strip. The strip is mounted on the bottom of the box. Challenge (or problem) solved. If you wonder why I didn't mount it at the center, the bolts would touch the variable capacitor on the inside.

Yes, I would like to have a bigger cap. This one is only usable for QRP powers. For now it does fine.

Mounted on tripod now.

80m configuration

Just to give you all an impression. Things might change in the future. So far I only tested range on 30m. But will try and test other bands soon. I want to test it outside as well although the loop is designed for inside.


Thanks for your comment. Bedankt voor je reactie. 73, Bas