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Old May 30th 09, 06:29 AM posted to rec.radio.amateur.antenna
John KD5YI[_3_] John KD5YI[_3_] is offline
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First recorded activity by RadioBanter: Jun 2008
Posts: 24
Default Loop antenna matching question


"Owen Duffy" wrote in message
...
"John KD5YI" wrote in
:

...
I seem to recall that a small loop has less inductance than a large
loop. I also seem to recall that the transformation between them is a
function of their inductances. So, a small loop would transform the
larger loop's impedance to an even lower impedance. Is this not so?


You can think of it in terms of inductance, but visit what inductance
really means (ie the relationship between inductance, current and flux).

I gave you an explanation in terms of area of the two loops. If your feed
loop os 20% of the area of the main loop, it intercepts 20% of the flux,
the voltage induced in the feed loop is 20% (1/5) of the main loop
voltage,



I understand this and I agree. It makes perfect sense.


the impedance is transformed by 1/(1/5^2)=25, so a 2 ohm main
loop is transformed to a 50 ohm load at the feed loop feed point.



This is the part with which I disagree. Can you show me why it is 25 rather
than 1/25?

(snipped section with which I agree)

Owen