DAVE : Wind yer coil of at least a hundred turns of magnet "war"
around a 1" PVC pipe segment (when I was a KID I used a lacquered
toilet paper core) and take taps off it every 2-5 turns (arbitrary)
and use the selector switch to derive signal from the taps that give you
the best performance (it will vary per band) The capacitors are from
old garage sale radios and may not even be needed

This accomlishes what you have already proven with your work, that
certain frequencies can be canceled out by selection of signal
inductor-load.in series with your antenna The capacitors merely
help you tune it in more making a tank circuit that resonates with the
frequency you're "working"

I did perhaps the same thing by winding 100 turns of magnet war on a
salvaice ring torid core from a ttransistor powwer supply off a dead
computer...The antenna went to 1 end of this 100 turns and the other end
was grounded. On top this hundred turns I wound 25-40 turns and ran on
end of THAT winding to my radio's antenna IN connector and the other end
to the radio's ground

You have just made a 4:1 balun...which all in one almost does what the
couple above does...no adjustment tho

Or you can do the quick and dirty trick with a TV 300 ohm to 75 ohm
coupler, connecting the 300 ohm end to the antenna and ground as above,
and the 75 ohm connectors to your radio's antenna and ground

You wont notice the difference

Yodar





Dave wrote:
The antenna does indeed seem to be working great, and the radio is not
operating too shabily either as it is only the "background noise" I am
trying to reduce. I hooked a 100 mH RF choke up to it with good results,
and am planning on adding another one or two similar devices in an
effort to
cut down on higher frequency interference. Question: how would I ground
this antenna? I have a grounding rod right outside the window, but don't
know what to hook it too. The negative battery terminal? This radio
does
have an external antenna input, but that has a plastic ring around the
outside. Open to suggestions. And thanks for the input RE purchasing a
new/used tuner.

dave

...






Private wrote:
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