"Michael Black" wrote in message
...
"Dave" ) writes:
I recently hooked up a thirty-six foot (plus or minus a couple of feet)
piece of four-stranded wire with alligator clip to the internal "whip"
antenna of my portable shortwave receiver, for the extra performance
such a
device offered. It works so well that I now cannot usually use my "DX"
setting because of all the background noise (sounds like hundreds of
other
broadcasts vying for attention.) I don't know the frequency source of
all
this background noise, but would like to filter out as much of it as I
can.
One manufacturer of a similar "wind-up" antenna adds a capacitor to the
wire
in order to lower the resonance frequency of the wire. If I were going
to
try something similar (adding a capacitor, in series) in an attempt to
bring
the resonance of the wire down into the 30 MHz range, what size
(roughly)
capacitor should I use? Should I just try a few with different ranges,
or
does anyone here have any suggestions?

TIA

Cross-posted between sci.electronics.basics and rec.radio.shortwave


Dave




It's probably designed for use with the whip, note the absence of
an antenna jack. It needs to be sensitive because it's using that
small whip, and when you add something longer, it overloads.

In other words, it's not one single signal, but all the strong local
signals, that are overloading it. TV and AM and FM broadcast stations
can put out pretty strong signals locally, and they can get around any
filtering in the radio, and still be strong, and then overload the active
stages in the receiver.

Michael


Just a quick note: it actually does have an external antenna input, I just
don't know what type of plug to stick into it. Plastic ring with metal
contact inside, looks like 1/8" mono would do it, but how would I ground it?
Negative battery term?

Thanks,

Dave