Ferrite Sleeve Antennas - Page 1
Forum section: electronics / rf-microwave

author: aweatherguy
author_rank: Contributor
timestamp: November 15, 2022, 05:22:30 pm
content: There's a post from last year on this topic, but rather than reply to that it may be better to start a new topic.https://eevblog.com/forum/rf-microwave/ferrite-sleeve-antenna/There's an analysis of these antennas available here:https://www.osengr.org/Articles/Loop-Antennas.pdfIt's a large document, with a separate chapter on FSL antennas. The gist of it is that while adding a ferrite sleeve to an electrically small loop of moderate diameter (e.g. 4-12 inches) will improve the performance, the gain is not as much as one might think (based on a lot of blog posts around the Internet). The issue is that while this analysis appears to have been well done using E-M simulation software, it is not backed up with experimental data. There are no real scientific comparison measurements of air core vs FSL antennas published today. The best one I could find is a fairly subjective analysis by DeBock.So, here's what I am wondering about. I'm interested in making some performance comparisons to vet the analysis linked above, but these FSL antennas are hideously expensive to build -- hundreds of dollars. Especially today since most of the really cheap Russian surplus ferrite rods have already been scooped up. While I would like to do the comparison, I cannot justify spending the amount of money which would be necessary to pull it off.I am wondering if there is someone who:Has built one of these FSL antennas, or knows someone who has and would let them borrow it.Has the equipment required to do a proper comparison.Means to measure the Q of resonated loops, preferably in situReceiver, spectrum analyzer, or similar which can accurately measure relative signal amplitudesCould build or acquire a similar air core loop for comparison.Has the time and inclination to do it.I know this is a lot to ask, so I'm not real hopeful about this...but it is at least worth asking.

author: radiolistener
author_rank: Super Contributor
timestamp: November 16, 2022, 09:23:32 am
content: Quote from: aweatherguy on November 15, 2022, 05:22:30 pmthanks, interesting article

author: aweatherguy
author_rank: Contributor
timestamp: January 19, 2023, 11:56:58 pm
content: Update in January, 2023: I've been able to build some FSL antennas now for testing, and the results seem to confirm the above analysis. The above reference article has been updated with those results.There's also a new article that is essentially an excerpt of the FSL chapter from the above link. You can find that here:https://www.osengr.org/Articles/FSL-Antennas.pdfIf you want to build an FSL antenna, or at least consider whether to build one, then this article provides a lot of good information.

author: coppercone2
author_rank: Super Contributor
timestamp: January 20, 2023, 08:16:41 pm
content: The results are a little disappointing. It's alot better engineering solution then a giant rod, especially if you really wanna scale it up.

author: TonyF1
author_rank: Newbie
timestamp: April 16, 2023, 09:50:19 pm
content: Expensive is correct. At least $160 on my part and it was a small one and that's using some stuff I already had.Like all MW loops, it hates being by structures, especially metal. It has to be out in the clear.Another thing I've noticed is that it favors certain AM radios. Some have almost no effect.I'll play with it but on reading the findings, a 10" air wound loop would be basically the same.Look's cool though.TonyF