Dave,

I have been in a very similar situation. I used almost an identical
antenna and had fantastic results. The radio likely does not have
sufficent filtering in this case (Antenna is likely working great). I
would start by ensuring the antenna has a good ground connection to
the radio.

An antenna tuner/preselector would defantely help. Purchasing a new
or used amateur radio tuner (i.e. MFJ) 1.8Mhz-30Mhz would be the
easiest option. Adding capacitors separetely could work, but from
experience is a challenge to achive an workable solution for all
frequencies.

Homac


"Dave" wrote in message ...
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