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