Without a balun, your feedline could become part of the antenna. If
noise is being radiated by such things as house wiring, the feedline
part of the antenna is likely to pick up more noise because it goes near
and into the house. A current balun prevents the feedline from becoming
part of the antenna and so it can reduce the noise.

A lot of local noise is predominantly vertically polarized. So if you
have a horizontal antenna without a balun, the feedline, which often is
vertical, can pick up a lot more noise than the antenna. Again, a balun
prevents feedline pickup and can make things quieter.

If you're feeding the antenna with coaxial cable, put the balun at the
feedpoint. If feeding with twinlead, put it where the feedline connects
to the tuner or receiver.

To learn more about baluns, see
http://eznec.com/Amateur/Articles/Baluns.htm.

Roy Lewallen, W7EL

Bill Ogden wrote:
A discussion on the towers reflector mentioned, in passing, that a current
balun helped lower received noise. The discussion was about something else
and this aspect was not explored.

Is this common? I had never heard of it before, but I many holes in my
understanding of antennas. Under what circumstances would this apply? Where
would the balun (toroids) be placed? Feed point or at bottom of tower? (My
particular interest is for use with a half sloper and for 160/80/40 meters.)

Bill
W2WO