I use an ugly balun with an attic GRrV and do not suffer significant
back-RFI to my transceiver in the regular frequency ranges. I think
that by chosing 1Kohm that may be a bit conservative. In (old)
engineering school, we tended to use an order of magnitude (X10) as
our highly arbitrary cut-off point for impedances that have a
significant effect. You are doing that too but by using 1000 ohms, you
are using (X10 times 2) as your arbitrary cutoff point. Since the
filter is an exponential curve, if you chose 500 ohms instead of 1000
ohms, you might even get a 4 or 5 to 1 frequency range. In my case I
use two different turns chokes so that is why I think I am covered
pretty well. Your information is very interesting; good to see people
are actually measuring things!


On Aug 28, 8:45*am, Cecil Moore wrote:
Highland Ham wrote:
Also: *http://www.hamuniverse.com/balun.html*(many pictures)
================
Nice URL with excellent info

The problem with ugly baluns is their limited frequency
ranges. In the following measurements, the choking
impedance was over 1k ohms for only small ranges of
frequencies, 19-29 MHz, 10-22 MHz, 16-25 MHz, 8-16 MHz,
5-8 MHz - frequency ranges of 2/1 or less. HF covers
a 10/1 frequency range.

http://www.k1ttt.net/technote/airbalun.html
--
73, Cecil *http://www.w5dxp.com