On Wed, 28 Dec 2005 05:25:49 GMT, David wrote:

On Wed, 28 Dec 2005 04:56:24 GMT, Bob Miller
wrote:


So you don't put high Z signal into a lower-Z cable. Major faux pas.
500 Ohms is assumed to be about the max for a wire antenna, no?

It can be much higher. Looking at the book "Wire Antennas" by William
Cowan, W6SAI, and his chapter on end fed wires:

"In the case of a random length, end-fed antenna, the radiation
resistance at the feed point can vary over a large range, depending on
the operating frequency and the actual length of the antenna. The
measured radiation resistance can be as high as 5000 ohms or as low as
2 or 3 ohms..."

That's why I wonder about the popularity of these 9-to-1 baluns.

One of my antennas is a 20 meter end fed wire, and I tune it with an
old Heathkit AC-1 antenna tuner, which is made especially for random
length, end fed wires. A modern equivalent would be something like the
MFJ-16010 random wire tuner, which at $49.95 doesn't cost much more
than some of the 9-1 baluns I see advertised :-)

It would require bringing the random wire into your residence, and
then running a short length of coax from the tuner to the receiver. I
understand some wouldn't like that because of in-house noise, but
there are always trade-offs to anything.

bob
k5qwg