Tim ODonnell wrote:
So now my question is this. Is my thinking off? I just want the best
reception that I can get. I just thought that a pre-selector might help.
Like Dan said below I really don't expect to use it all the time. Just when
it may help.

You can hear down to the internal noise of the receiver. If the antenna brings the
propagating noise up over that level, no further improvement in the antenna will help,
except making it directional to favor signal or disfavor noise, if noise is directional.

Modern receivers are very sensitive, but tend to succumb to overload and cross modulation
that results (hearing anything loud in lots of places instead of the one it's at).

A preselector kills off loud things that aren't where you want to listen, giving you
the ability to get a little bigger antenna to work for you, up until it exceeds the
internal noise, and then a bigger antenna doesn't help again.

So you get the possibly small improvement between hearing propagating noise and
the intermodulation limit somewhat expanded, is all. The usual experience though
is that the preselector ``reduces the signal,'' because you tend to compare it with
the big antenna without preselector and not the built-in whip.

They put a preselector on some active antennas because of the intermodulation; other
active antennas (McKay Dymek DA100E) have lots of headroom and don't need the
preselector, and so you don't have to tune it. It may still overload your receiver
though, for instance almost any portable; and then you have to add a preselector
because of the receiver. It doesn't overload an R8B.
--
Ron Hardin


On the internet, nobody knows you're a jerk.