In an earlier post (see Help!! Antenna Noise), I detailed how I live on
the 9th floor (top) of an appartment block, had built a 1/4 wave
vertical antenna, using a balcony railing as the counterpoise. When
the antenna was connected to my handheld Yaesu VR-500 receiver
(scanner/comms receiver), the result was noise at 8+ S units...

Two people very kindly responded to my original post, and suggested
what I might do to find where the problem was. The antenna is picking
up noise from somewhere (not the counterpoise or the connecting coax,
they exhibit no noise when connected in isolation to the main antenna).
Neither was the problem to do with the receiver being overwhelmed by
the signal, as I drove into the countryside, setup the antenna, and the
signal was fine...

I then tried the following:

1) Connected the small helical antenna that comes with the VR-500 and
the noise
VANISHES. Good.

2) Connected a simple half metre telescopic antenna to the VR-500,
and the noise returns. Not good...

Question: The helical antenna with the VR-500 obviously has some kind
of loading coil, at the BNC plug end. So I was wondering exactly what
kind of loading/matching, would there be in this antenna, that is able
to sucessfully kill the noise that plagues me here in Brussels,
surrounded as I am by tram and train lines (assuming this is the
problem of course)?

Could I build something like this to filter the noise being picked up
by my antenna? Any ideas? Circuit diagrams?

Thanks!!

Tim

On 7 Aug 2006 13:52:16 -0700, wrote:

So I was wondering exactly what
kind of loading/matching, would there be in this antenna, that is able
to sucessfully kill the noise

Hi Tim,

Absolutely none.

Try carrying your receiver around with that same small helical antenna
attached, and turned on for monitoring. Walk through the hallways
nearby your apartment on your floor, and the floors above and below
you.

Go outside and do the same around the block. All of this shouldn't
take more than an hour and should be conclusive. As you go along, you
might try alternating between the small helical antenna and the simple
half metre telescopic antenna which does pull in this noise.

Finally, what does the noise sound like?

73's
Richard Clark, KB7QHC

On 7 Aug 2006 13:52:16 -0700, wrote:

Could I build something like this to filter the noise being picked up
by my antenna? Any ideas? Circuit diagrams?

Thanks!!

Tim

A SHOT IN THE DARK!!!

This doesn't answer your question, but another.... What might be
causing the noise?

I had a couple of different 2 meter whip antennas with a base load for
the ht. One developed a problem with a bad solder joint which created
a diode effect, which acted like a receiver. It messed up my receive
something terrible. It never happened with the other antennas, but
they were built similarly. The rubber duck doesn't have the tuning
capacitor etc to match it as the whips did.

I think my antennas worked opposite yours. I had the 5/8 go bad and
the rubber duck work fine.

Other 1/2 wave and an unknown length whip work well without a problem.
The 1/2 wave and 5/8 wave whips both had tuning circuits in them.

Good luck
Buck
n4pgw

--
73 for now
Buck
N4PGW