"Bob Bob" wrote in message
...
Yes I know I can look this up....

Am currently feeding a 20M single triangular quad loop about 3 metres
off the ground with a 1/4 wavelength 75r Q section. Modelling the loop
shows a high-ish Z of 180 ohms. Not a problem for this feed method
though. (I expected it to be around 120 ohms)

Thinking of making it work on 10M and Z I think is around 350 ohms, but
I havent modelled it.

If I use a 4:1 coaxial balun cut for 20M, does the 4:1 effect (now a
full wavelength) also occur on 10M?

(Thinking a 3/4 wavelength Q section is the same as a 1/4 wavelength one
when it comes to translating the Z)

I am not and will not be using a tuner... (in case anyone wants to
suggest it)

TIA Bob VK2YQA

Instead of a coax balun, its easy enough to wind your own using a toroid,
and a 'transformer-type like that has a wider bandwidth.
those 1/2-wave u-bent baluns are good for one band usually. what you're
doing is catching the phases where the difference in voltage is twice normal
voltage. (Doubled the voltage) square that, and your impedence is
quadrupled.
If you triple the voltage, the impedence increases by 9. If you wind a
transformer you can make it close to any impedence you want....
lets say you have a length of coax is a 1/2-wave on 14.2 mhz
it would be a full wave on 28.4 mhz
it would be 3/4 wave at 21.3 mhz




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