Walt, not to take a thing away from your W2DU balun. I suspect you have
never characterized it at high power.

The #73 material gets really hot at higher power.

"Walter Maxwell" wrote in message
...
On Tue, 23 Aug 2005 16:58:14 +0000 (UTC), "Reg Edwards"
wrote:

The only things I know for sure is that no balun covers from DC to
daylight,
or even 1.8 to 30 Mhz.

==============================
Fred, I'm afraid you're wrong.

Slide a sufficient number of ferrite beads over the coax line and it
will easily cover 1.8 to 30 MHz. Alternatively, wind sufficient turns
around a largish ferrite ring of the correct grade of material.
----
Reg.

Reg is right, Fred, the W2DU balun with 50 #73 beads was designed to
cover from 1.8 - 30 MHz. The series impedance along the outer
conductor of the coax at 2.0 MHz is just over 750 ohms. If the antenna
operating at 2.0 MHz is a half-wave dipole, half the dipole impedance
at resonance will be around 35 ohms. The ratio 750/35 = 21.4, which
gives an approximate isolation of the common-mode current of 26.6 dB
below the current into half the dipole, which is more than adequate.
If you want still more, make the balun with more than the original 50
beadss.

If you don't have a copy of Reflections you can find the balun data
from my web page at www.w2du.com. See Chapter 21, page 21-8, for the
graph that plots the resistance, reactance, and impedance of the
outside surface of the coax in the W2DU balun vs frequency.

Walt, W2DU