Many thanks to SWLing Post contributor, Zoltan Azary, who has written an extensive theoretical analysis of ferrite sleeve loop antennas. This article has a very academic flavor and for those who are interested in antenna design, he welcomes your comments!
Thank you for sharing this work with us, Zoltan!
I wrote an article about mine in Radio User, after making contact with the inventor(?) Graham Maynard. An interesting bloke with some er… challenging ideas and opinions. I believe he is no longer with us. I still have the antenna and I take it on holiday with me so I can hear distant sigs on MW and Topband. It has 39×5″ rods and measures about 6 ins in diameter.
I position it near my portable radio and the improvement is huge. Listening to my Manchester-based 1963 kHz AM net in Norfolk a couple of years ago I could barely hear any of the station directly on my portable, but putting the FSLA near the radio and adjusting for resonance brought them up to not quite ‘armchair copy’ but certainly easily readable. The Q seems very high and tuning is sharp even with a slow motion drive on the capacitor.
As far as noise rejection goes, I’ve found mine to be about the same as a standard single ferrite aerial, ie much better than yer typical wire aerial.
Ferrites are frequency sensitive as shown in https://www.fair-rite.com/files1/Fair-Rite_Catalog_17th_Edition.pdf which are one of the brands available at some of the larger electronic component internet suppliers.
Yes, 100% correct. Could the article be improved by a more in-depth discussion of this?
Many thanks for this.
Thank you for posting this research. Quantifying why this works is worth documenting. Also, the “fat stack” looks interesting as a way to save weight and space to get similar results.