"Alan Peake" wrote in message
...


Heliax or semirigid coax might cause them to give up. Especially the
latter. 75 Ohm stuff would be fine for the 4:1 balun, because you
actually would want it to be 100 Ohms.

Tam/WB2TT

100 ohms? This is just a half-wave coax balun. All the books say it should
be 50 ohms - same as the feed and the yagi. The only place where a
different Zo is used is where the four yagis combine. There, a quarterwave
section of TL of Zo=25 is used to match the 12.5 ohms of the four yagis in
parallel to the 50 ohm main feeder.
The main feeder is heliax so the birds haven't got to that - yet. (Tough
birds down here in VK!!)

Alan

It is a 200 Ohm antenna. Each half is 100 Ohms to ground.When you put the 2
sides together you get 50 Ohms. Since the line is 1/2 wave long, any
impedance will work, including 50. CushCraft made a beta match 6 meter beam
which used a 1/2 wave section of RG11 75 Ohm coax. People have also use 93
Ohm coax, but its loss at 1:1 SWR is probably more than RG8 at 2:1 .

Tam