Usually a balun is used to connect an unbalanced feed line, such as
coax, to a balanced antenna such as a dipole. The balun should improve
the current distribution on the dipole and reduce the current on the
outside of the coax. This makes the dipole have a closer to text book
radiation pattern. If the pattern changes, depending on where your local
noise sources are, the noise level could either increase or decrease,
indicating that the balun is doing what it is supposed to do. One would
expect that local noise sources are likely in your house, and making the
feed line work more as a transmission line and less as an antenna, by
reducing the current flowing on the outside of the shield, you would
hope that the noise would be reduced when using a balun. The total noise
power from any given noise source is the combined power picked up by the
"intentional antenna" and the feed line, the "unintentional antenna".
Those two components may be out of phase, partially canceling each
other. The total noise power to the receiver could actually increase
when the balun stops the current on the outside of the coax.
DE N6KB
Denton wrote:
> Not really a ten tec question...but this little group seems to be
> particularly knowledgable...
> I am tinkering with an 80 meter inverted L antenna, and I noticed that when
> I hook up any kind of balun at the feedpoint, the signal to noise is much
> more prevalent than when feeding the L directly with coax.
> The L has a few radials attached and shares a common ground rod with the
> radio station ground.
> Wonder whythe worse signal to noise. Thanks...
>
>
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