"Ian White GM3SEK" wrote in message
...
Suzy wrote:
I am building a 70 cm Yagi. I want to make a balun out of a loop of coax
(yes, I know there are other methods but I prefer this one). My question
is,
will rg58 do. Also, comparing like losses to like losses, should it be 50
ohm or 75 ohm and why?

RG58 will do fine. Some constructors use small hardline such as UT141, but
mostly for mechanical convenience. At this wavelength, larger cables are
quite difficult to bend into the small loop this is required.

Since the balun loop is an electrical half-wave, any impedance will
reproduce the same voltage at the other end. (Minor details: cable loss
will have a small effect on voltage balance, but probably not enough to be
detectable; the optimum impedance for VSWR bandwidth would be 100 ohms,
but that is unimportant because other parts of the yagi will probably have
a larger effect.)

In summary, choose whatever cable you can conveniently form into an
electrical half-wave loop.



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73 from Ian GM3SEK

Thank you so much Ian. Definitive answer at last (yes maybe the others were
too, Owen, but I am too thick to fathom them. g)