Topband: Common mode chokes

[Richard (Rick) Karlquist]

GEORGE WALLNER wrote:

> 
> On a separate note, I have been experimenting with twisted 
> pair RX transmission lines. I have used a twsited pair 
> removed from a CAT5 cable. With a well balanced 
> transformer and a common mode chocke at each end, it seems 
> to have very high common mode rejection (i.e. I have not 
> been able to measure it). Loss at 1.8 MHz is about 0.7 dB 
> / 100'. Note that for good common mode performance, the 
> line should be away from other conductors.
> 
> George
> AA7JV

I have used CAT5 pair to make transmitting transformers
at the legal limit up to 7 MHz.  They give you a very
good 100 ohm line for no effort.  I have also used them
for short (30 foot) feedlines for cloud warmer dipoles.
That way, I don't have to have a balun at the center
of the dipole.  I use two pairs in parallel to get 50 ohms.

Rick N6RK