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Ultrasonic
Direction Finder JUMA UDF1
I designed this Ultrasonic Direction Finder to find arcing insulators
in high voltage power lines. An arcing insulator can generate very strong
wide band RF noise. Typically you can recognize insulator arcing noise by
using noise
blanker (NB)
which may reduce the interference as opposed to other noises eg switching
power supply noise which can't be reduced with noise blanker. Arcing insulators
generate ultrasonic sound. With this UDF1 you can find the pole or even
the particular insulator which is arcing.
Power grid companies are happy to know an arcing insulator to make
preventative repair before the insulator will fail completely. This way you can get
rid of this bad arcing RF noise.
The receiver is using a direct conversion principle to convert
ultrasonic 16kHz-50kHz sound down to audio frequency range. Additionally
this finder can be switched to direct audio frequency sound receiver by stopping
the local oscillator with a switch on the PCB.
Click the photos to enlarge. |
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34cm wok pan lid parabolic reflector
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Rear view with the wooden handle
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Pekka OH1TV testing UDF1
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| I am using a 30 cm wok pan
lid which has not a precise parabolic shape. I used sunlight and a piece
of paper to find a best focal point. You can use a alike lid or a real parabolic
dish. The diameter can be from 30 cm up to any practical size. I tested several
electret microphones in ultrasonic frequency range and I found that the
smaller the better. WM-62BT microphone was the best with a diameter of 6.0mm
and thickness 2.7mm. |
Electret microphone WM-62BT
soldered to a semi rigid coax.
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PCB and handle left view. Handle angle is 10 degrees. |
Front view with BNC bulkhead
connector for the microphone. |
The wooden handle is screwed
to a 1mm aluminum chassis. |
Power switch is right down, audio/ultrasonic
selector switch is left up.
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Tune and gain potentiometers. Headphone
connector is a 3.5mm jack.
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I also tested a real 12 inch parabolic reflector from Edmund Optics. It provides much better focus and thus better directivity. On the other hand the wok lid has a workable performance.
Parabolic reflectors from Edmund Optics
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Edmund Optics Parabolic in use |
50 x 50mm Al piece is needed to reduce
the 19 mm hole
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JUMA UDF1 block diagram
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