Hi Don
I have built the same Ultrasonic receiver and its no slouch. I have access to a
UE Systems Ultraprobe 15000 with its associated dish. Anything that I can
detect with the UE15000 I can hear with the W1TRC receiver. The UE system can
tune from 20khz to 100khz, however I did not find that any particular
ultrasonic frequency to be better or worst. Although from this reflector
someone reported that the RE 250/251 dishes use 30khz as their detection
frequency. I have not confirmed this.
I used a weak spark signal source from a Wirmshurst Generator that I bought as
a kit. It has much less spark intensity than the Spark plug tester. I also used
a old model T Ford coil which really made a lot of noise that was strong. Its
easy to adjust the gap for a weak spark.
http://www.sparkitelectrostatics.com/
Many of the BAT detectors are using MEMS mics. I also came across the blog of
KA7OEI which has many articles on RFI and Ultrasonic equipment. He has been
experimenting with the MEMS mics which offer a wider frequency response with
better sensitivity than the ultrasonic fixed frequency resonators.
https://ka7oei.blogspot.com/2026/03/modifying-mfj-5008-parabolic-ultrasonic.html
I have not done the MEMS mic mod yet since I am waiting on the MEMS mics from
China which is already mounted on a PCB.
I Have both the Duncraft Squirrel dish as well as professional Spun Reflector
from Edmund Scientific. In reality there is not much difference because of the
propagation limits of the ultrasonic waves. I could not replicate the 200ft
detection range as reported in the QST review for the MFJ unit. The QST review
also indicated that the RE250 had a great range than 200ft which even the UE
15000 could not detect. I found it more reliable to use my air compressor with
different size nozzles to create a tiny leak as a weak signal source.
73
Craig
VK3OD
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