[TowerTalk] VHF/UHF Transmitting Chokes

[jimlux]

On 3/7/20 12:42 PM, Jim Brown wrote:
> On 3/7/2020 11:47 AM, Richard (Rick) Karlquist wrote:

>>
>> I notice that the 6 inch diameter 2 turn loops
>> have a free space electrical length of exactly
>> 1 radian at 50 MHz.  Is that just a coincidence,
>> or is that in some sense optimum? 
> 
> It's a coincidence. I looked at Fair-Rite's data, noted above, wound 
> some chokes and measured, and liked what I saw.
> 
> Harold Wheeler
>> coined the term "radianlength" and noted that
>> it seems to be magic length where systems transition
>> from lumped element to distributed elements, etc.
>>

It's like that old Tesla coil thing about the secondary winding wire 
length needing to be 1/4 wavelength at the operating frequency.  Indeed, 
that is where many coils happen to wind up, but it's sort of a 
coincidence, because the coils have similar length/diameter ratios and 
number of turns.

There have been folks who have attempted to model a tesla coil as some 
sort of slow wave structure (essentially a transmission line with a very 
high L/C ratio, like that delay line coax with the spiral center 
conductor), but lumped models work just as well.