A 1:1 choke balun made out of coax "chokes" off current flowing on the
outside of shield, it has no effect on what is happing inside the coax
between the inside of the shield and the center conductor. If you made a
choke balun wound on a toroid or with beads with 2 foot of 75 ohm coax and
used it on an antenna with a Z of 50 ohms at 28Mhz. That 2 foot of 75 ohm
coax would transform the 50 ohms to 59.4+j21.3 ohms at the output end of
your balun. If this is a problem it's up to the user to decide but I
wouldn't like it. The same effect would happen if the balun was made with a
parallel conductor line be it "zip cord" or enameled wire. If the Z of the
line in the choke balun doesn't match the Z of the feed line it will cause
an impedance transformation that will with vary with frequency. Of course if
one is only using the balun at 7Mhz or lower it will not be as noticeable as
it is at 28MHz.

--
John Passaneau, W3JXP
Penn State University


"Reg Edwards" wrote in message
...

Anyway
the difference in loss between #18 wire and RG-400 due to IR drop in the
length of wire in a balun is too small to worry about.

John Passaneau, W3JXP
Penn State University

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Just like I said !

But a 1:1 choke balun has an indeterminate transformation ratio.