Re: Gary's New 6" FSL Design

Gary DeBock

<<<   Hi Gary,
Your new 6 inch FSL is a step towards higher gain in a relatively small package. I look forward to a YouTube review.   >>>

Thanks Todd,

The master plan behind this new 6" FSL design was to use all the high-Q components discovered in the compact, airport-friendly FSL experimentation and combine them with powerful ferrite gain. The performance results do seem worthy of the effort, and I'll try to post a demo video soon.

<<<   Regarding 1162/46 Litz wire used in the 6" FSL, what is the cheapest source of supply that you have found so far?   >>>  

I always use the 1162/46 Litz wire from the eBay seller "Mkmak222," which runs US$1 per foot. Of course this is pretty expensive for the average experimenter, who will need about 32 feet to make a Medium Wave FSL, not to mention the 60-watt soldering iron required for proper installation. There are many cheaper varieties of Litz wire available such as 660/46 and 330/46, and unless a DXer absolutely needs the highest sensitivity in the most compact antenna (such as for overseas air travel, etc.), the cheaper Litz wire is OK in most applications.

<<<   On AU eBay, 1162/46 Litz wire is quite expensive. Assuming 19 turns in your design, when I build one, there should be at least 1 or 2 extra turns to allow ferrite rod permeability variation.
21(6 x 3.1416) = 396 inches or 33 feet of wire.    >>>

Yes, 33 feet would probably be the minimum safe length of 1162/46 Litz wire to use for an MW coil if you are not sure how all the manufacturing differences will shake out in the final tuning range. It's no fun to wind an MW coil, and then find out that it won't tune down to 530 kHz because your variable cap doesn't have as much capacitance as your previous model.

<<<   The cheapest 1162/46 Litz wire on AU eBay is US $88 for 60 feet. No smaller minimum 33 feet length is available.

Yes, this type of Litz wire should be reserved for fanatical DXer projects, in which you tweak a tiny antenna into an outrageously sensitive, ridiculously effective gain monster for the tiny size. I've posted a 3" Baby FSL video to show this effect. But the expense of this Litz wire is steep, and probably unnecessary unless you absolutely must have a tiny little DXing "firecracker."

<<<   With tank coil Q > 500, the bandwidth will average only 2 KHz or less. The audio fidelity will be compromised as a result. Resonant tuning peak will also be sharper. Higher Q = narrower RF signal bandwidth, degraded high frequency audio response, but high signal strength when tuned to resonance.   >>>

All certainly true, Todd. The highest "Q" FSL antennas have the narrowest bandwidth, which causes some loss of high frequency audio from a DX station. This compromised audio can be somewhat improved by audio processing software, but a razor-sharp-tuning FSL antenna will always clip off some high frequency audio when its frequency matches that of a weak DX station on an Ultralight radio. It's part of the game, and you learn to use the audio processing software to compensate.

<<<   During the process of testing various early design FSLs, what did you find by using lower resistance wires regarding varying degrees of S/N readability, bandwidth, and audio quality? For an air core loop with 1000 Q, the audio will be quite muffled at 531 KHz.   >>>

The early FSL's had pretty low Q, wimpy sensitivity from their smaller Litz wire and relatively good audio from the Ultralight radios. The latest high Q gain monsters sacrifice some audio quality in an all-out pursuit of the highest sensitivity, and their 1162/46 Litz wire will drain your bank account. But all is forgiven when an S9+ Kiwi DX signal thunders across the ocean at over 7,000 miles when you are on an ocean side cliff-- especially one which rarely shows up at all on a flat ocean beach.






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