[RFI] Ultrasonic Line Noise Detectors

[Rick Karlquist]

The QST project reportedly works, but is far from an optimal design.
The high gain (read narrow beamwidth) transducer recommended
doesn't properly illuminate the very low f/d dish and the
frequency down conversion scheme adds needless complexity.
I built my own version using the widest available beamwidth
transducer and a simple envelope detector that hears 60
Hz modulation on the narrowband 40 kHz signal.  I mounted
a green laser pointer on it to illuminate the point on the
pole that I am pointing at.

Rick N6RK


Jimk8mr at aol.com wrote:
> In the May issue of CQ my eye caught an ad for  an Ultrasonic Receiver Kit
> (page  113):
>
> http://www.midnightscience.com/ultrasonics.html
>
> This appears  to be essentially the entire receiver portion of the W1TRC
> ultrasonic powerline  noise detector that was in QST a few years back.  I
> built the W1TRC device  and have found it useful for isolating power line
> noise.
>
>
> It seems  to me that remoting the ultrasonic transducer (microphone) out
> of
> this kit into  the parabolic dish of the W1TRC design would give you an
> complete ultrasonic  detector.
>
> You may want to check these out.
>
>
> 73    -   Jim  K8MR
>
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