[Elecraft] Semi OT: ratios of unun windings

[alta]

Mike ...

It makes sense to me.  And may not be too critical for LF 
receive-only.

For HF transmitting, I know that other important factors are: the 
spacing between the tri-filar conductors and wire size (the resulting 
impedance), core material, core size, and number of turns for the 3 
windings.

... Reed

On Thursday 10 January 2002 19:01, you wrote:
> Good evening, all.  I'm in the process of beginning to experiment
> with a wanna-be Beverage, and had a question about winding an unun
> for it.  Through the ARRL Handbook & Amidon's literature, I've
> calculated the number of primary & secondary turns needed for the
> chosen core.  BTW, the antenna is for LF, receive only.
>
> I've come up with a ratio of 18:54 turns (50 ohms:500 ohms).  Is it
> permissible to reduce this to 9:28, or even 3:9?  As in, I assume
> the magic isn't in the exact number of turns, but rather the ratio
> between primary & secondary windings.  Although 1:3 would be the
> next step, I get the feeling that this would not allow for adequate
> coupling between the windings.  Working the formulas backwards, the
> 3:9 actually turns out to be a 50 ohm:450 ohm match, which is still
> adequate for my testing (since the impedance of the antenna at LF
> is only an estimation anyway, and is only for receiving).
>
> Does all this make sense?
>
> 73,
>
> Mike Boice, KW1ND
> Nampa, Idaho
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-- 
Reed White  -  ALTA RESEARCH  -  www.alta-research.com
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