John G3PQA wrote:
> For those who wish to build an ultrasonic detector (or in the absence
> of DX locate bats!) an article was published by ARRL in
> 2006http://www.arrl.org/files/file/Technology/PLN/Ultrasonic_Pinpointer.pdf
> I have built a couple of this design using the Far Circuits pcb and they
> work well, needs a small parabolic dish and piezo electric detector at its
> focal point.
> Also I should mention that Jerry K4SAV has designed some improvements in
> sensistivity and mixing if needed.
>
This is a very useful device at pinpointing a problem. If the noise
source is not very close to you, a radio of some kind will be needed to
get somewhere close to the source. When in the area, a check of each
power pole with the ultrasonic detector will usually locate the
problem. In all cases I have been able to determine which item on the
pole is the problem. It's amazing how quick the service can be when the
power company doesn't have to do any work at locating the problem. In
one case I called in a problem, telling them it's the surge suppressor
on the top north corner of a specific pole. Two hours later the noise
disappeared. I couldn't believe they fixed it in that time, I was
thinking oh no it's gone intermittent, so I drove to the area and they
had disconnected the surge suppressor.
I also found it amazing at the distances that can be involved in these
noise problems when the source is loud. The example above was 3 miles
from my house and the noise level at my house was S9 (on 160 meters). I
have identified two problems in that area, both of which were fixed, but
the area continues to emit noise that I can hear. I'm sure there are
more smaller problems there. When the source is that far away, if you
just call the power company any complain, they will never find it.
The only source that I never found using the ultrasonic detector turned
out to be a plasma TV in a house about 1500 ft from my antenna.
Fortunately they moved less than a year later.
The biggest problem I have when using this is that when I start looking
I usually find multiple noise sources. When at a considerable distance
from home most of these sources are not audible and it's sometimes
difficult to identify exactly which one is the one causing the problem.
If the source has a particular characteristic then it's a piece of cake.
Note: Don't get fooled by the bats and the grasshoppers at mating time.
They don't really sound like noise, but more like a data channel.
Jerry, K4SAV
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UR RST IS ... ... ..9 QSB QSB - hw? BK
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