[IRCA] Winter FSL Antenna Experimentation

[d1028gary@xxxxxxxxxxx]

Six years after Graham Maynard's introduction of modern FSL antennas the design continues to be somewhat of a specialty item-- often considered to be too expensive, heavy or complicated for the majority of MW-DXers. Despite several attempts to publish "Heathkit-like" construction articles for reasonably-priced FSL antennas (and having numerous builders successfully complete these, as documented in videos such as https://www.youtube.com/watch?v=YdzCJbNrTno ) I've seen the eBay sellers of Russian surplus ferrite take advantage of the increased demand by raising prices repeatedly. As such, as soon as an attempt is made to design and publish an inexpensive but effective FSL antenna design the eBay ferrite sellers end up derailing the "inexpensive" part of the design plan. 

In order to counter this a major effort was started this winter to design very small but effective FSL antennas, using the minimum number of ferrite rods. In order to compensate for the smaller coil sizes the ultra-sensitive 1162/46 Litz wire was used in all of these "Baby FSL" antenna designs, giving these tiny antennas an unusually powerful inductive coupling boost for their size. Of course the smaller (and more economic) 660/46 Litz wire can also be used in these designs, if desired, but the breakthrough gain boost provided by the 1162/46 Litz wire is a major performance improvement. One of the new 3.5 inch "Baby FSL's" with the 1162/46 Litz wire can roughly compete with one of the original 5" FSL's with 660/46 Litz wire (which in turn was favorably tested against a 4 foot air core loop, as documented in the 2012 construction article posted at http://www.mediafire.com/file/9ze98h293s85p86/5_inch_FSL.doc ) 

A full "Heathkit-like" construction article is planned for this new 3.5 inch "Baby FSL," which uses 32 of the Russian surplus 140mm x 8mm ferrite rods and 31 turns of 1162/46 Litz wire (shown in a demonstration video posted at https://www.youtube.com/watch?v=WYuikQj7yPA , where it boosts a daytime DX signal from 750-KXTG up from S0 to S7.). A couple of even smaller "spinoff" FSL antenna versions have also been designed, one using 27 and another using 24 off the 140mm x 8mm rods. The latter FSL model can be built for under $99-- which was true of the 5" FSL model back in 2012 (before the ferrite sellers cashed in). 

Finally, a new class of "Frequent Flyer" FSL antennas is being developed, specifically to pass easily through airport TSA security checkpoints. They all use the very thin (3mm thick) ferrite bars instead of ferrite rods-- which might have the appearance of a ring of dynamite to a vigilant TSA security agent. The thin ferrite bars are practically invisible in these designs, making the antenna look like a simple coil and variable cap. The first 3 inch "Frequent Flyer" FSL model has already been developed (demonstrated at https://www.youtube.com/watch?v=_YLrLsjsXmQ , where it boosts a daytime DX signal from 750-KXTG up from S0 to S6), and 5 inch and 7 inch models are being developed. Unfortunately these Russian surplus 100mm x 20mm x 3mm ferrite bars are very scarce, though, so a full construction article for these "Frequent Flyer" FSL models isn't planned. 

73 and Good DX, 
Gary DeBock (in Puyallup, WA, USA) 

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