I’ve fallen behind with my blog posts and I started this one ages ago…its really in the gear review category and I’m definitely not starting down that path.
However, I see very little mention of Magnetic Loop in our community and after a serious amount of “up close and personal time” with one you can, if disposed, see my journey from disbelief to ardent supporter.
I bought a DL4KCJ 2-metre “diametre” omega-fed asymetric square magnetic loop at Friedrichshafen HAM RADIO show this year from the designer for a “reasonable price” but as yet it hasn’t found it’s way to a SOTA summit - I am in the process of adding a reduction drive and vernier dial to make the tuning more precise.
I looks like it should work on 80m through 12m although 10m could be a problem.
Last year, I also spent quite some time experimenting with magnetic loops. My essence is:
A small one, like AlexLoop etc. ( +/- 1m in diameter) is most suited for hotel room / balcony operation when least visibility / stealth mode operation is key. Performance wise, most alternatives (e.g. a resonant or random vertical, even with a short 5m radiator are superior. Also, the additional benefit of additional front-end filtering is most useful near hotels with their thousand sources of RF noise, not so much in mother nature.
For SOTA operations, I find them too heavy and too bulky, to slow to tune and set-up. Also, their performance on 40m, which is my bread-and-butter band for SOTA, is unsatisfying.
If it can be a bit bigger, like 1.6 - 1.8 m in diameter, it can be a very interesting option. I used one at my QTH with a simple remote-control mechanism, and it allowed for quite some NA DX with 5W.
So I think they are interesting, but not so much for SOTA.
73 de Martin, DK3IT
Bigger is better. Always.
Yes, but what I wanted to say is that
- I was quite disappointed by the small magnetic loops in the typically advertised sizes, and I think they are unsuited for SOTA purposes in most cases,
- but I was quite excited by their performance when the circumference is 5 - 6 m.
Anyway, I did not want to start a fierce debate about whether magnetic loops are good or bad
73 de Martin, DK3IT
I built one of 1.45m diameter loop with an electrically fully disconnected coupling loop of a 1/6th of the diameter of the main loop and a 250pF variable capacitor. It worked fine on 17, 20, 30 and 40m. I have even tuned it on 60m, althought never got to make a QSO on that band.
Reception is good and always extremely quiet and comfortable.
Used for SOTA on a couple of drive-on summits. Worked S2S with a VE2 activator on 20m CW with 5 watts from our Atlantic Ocean coast EA1/CR.
Also worked FO French Polinesia on 17m CW with 5 watts and the magloop in the balcony of my QTH in the Village near Pamplona.
Althought it’s clearly very impractical for the type of SOTA activations I like doing, I love this home built antena and I will add a small capacity variable capacitor in parallel and a special mechanism to ease the tuning operation for 1:1 SWR one of these days. But finding the time to do these simple projects is something I find extremely difficult in these days…
P.D. You can see it on my QRZ.com
Magnetic loops work but they are inefficient radiators compared to most other antenna types used by SOTA operators. However efficiency is only one characteristic of an antenna and the desired balance between efficiency/performance and other factors such as usability are very much a personal choice (which is why people don’t agree).
Owen Duffy has a great many posts on magnetic loops which explain what the actual efficiency of such systems is likely to be: