Re: "Spiked" Mini-FSL Antennas

Guy Atkins

Hi Gary,

I'm looking forward to your further mini-FSL adventures! Perhaps we can meet again next week to discuss... I'm on vacation from Christmas through Jan. 4th and will have some free time.

I had always assumed that the larger Litz wire was only appropriate for the larger FSLs, to maintain some sort of proportional increase over the typical wire diameter found on standard (stock) ferrite rod antennas. Now I'm suspecting that thin, lower grade Litz is just a cost savings measure by the manufacturers, and/or to keep the "Q" bandwidth wide enough for the general consumer's tastes versus DXers' interests. Congrats on thinking outside the box again :^)

In case it hasn't been mentioned on the group before, I'll list a URL which I think is handy for FSL calculations:

Smaller Circles in Larger Circles

Using this web based calculator saves some manual steps to figure out how many ferrite rods will fit on a larger cylindrical core, or conversely to calculate the diameter of a core needed when you have a certain number of rods to use. This tool assumes using the smaller circles *within* a larger one, but since FSLs use rods on the outside of the form or support, I just subtract 2X the rod diameter (typ 10mm) from the calculated result to come up with the core diameter. For FSL purposes you can ignore the "fill" circles since a hollow cylinder of ferrite is needed.

This calculator works better for smaller FSLs, since it's easy to count the outer layer circles in the graphic that's automatically generated.


Guy Atkins

Puyallup, WA

---In ultralightdx@..., <D1028Gary@...> wrote :

What would happen if someone took the most sensitive Litz wire available on the commercial market and installed it on midget-sized FSL antennas? Would the models simply get a minor boost in sensitivity, or would they become tiny little terrors? Meet two of the new, 2016-model midget FSL's-- designed to provide a major upgrade in both excitement and affordability. 
Although the 2012 version of the 5" FSL antenna (construction article posted at ) was designed to match the performance of a full-sized 4' box loop and has been successfully built by many hobbyists, there have been several newer types of more sensitive Litz wire introduced during the past 4 years. The most sensitive 1162/46 Litz wire was first sold in 2013, and installed immediately on the monster FSL antennas used for Oregon Cliff DXpeditions (with dramatic effect). Until now, though, nobody had tried doing the same thing with mini-FSL antennas.
As it turns out, installation of the super-sensitive Litz wire makes the new 3.7" and 5" diameter FSL models behave much like the Oregon Cliff Monster Loops, with powerful inductive coupling boosts, razor-sharp tuning and astonishing performance. They are also designed to be affordable-- the 3.7" model can be built for under $100 as of this date, and the 5" model for under $130 (design photos attached). These all-new models are designed to incorporate all of the positive component changes over the past 4 years, and help you avoid the negative changes. They are two of the FSL's being introduced in an upcoming experimental article, which will contain full construction details for these and other innovative antenna models. Have a happy and exciting New Year!
73, Gary DeBock (in Puyallup, WA, USA)   


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