Ultrasonic Detector: Midnight Science RX-2 and 12″ Dish

After reading “AC Power Interference Handbook” by Marv Loftness, and based on my own experiences trying to identify sparking poles at VHF I decided to add an ultrasonic detector to my power line noise hunting arsenal. The question was which unit to try. Commercial ones start around $3500. If I had the disposable income most DXers seem to have these days, I probably wouldn’t bat an eyelash at that. If it helped get my hobby back it would be well worth it. However, since I was already selling off bits of my station in to be able to buy low-end noise hunting apparatus,  those were out of the question. It came down to two options: it was either going to be homebrew based on the article by W1TRC or the Midnight Science kit offered by the Xtal Set Society. Unfortunately there wasn’t much solid information on how effective either unit is in practical deployment. I found a lot of others wondering, but nobody providing information to shed any light on the matter.

Having finally decided on the Midnight Science offering, I ordered an RX-2 receiver and the companion 12 inch dish kit. This isn’t intended to be a product review but upon opening the box I was immediately disappointed with the dish. It is quite flimsy and arrived deformed so that it did not conform to a true parabolic shape. For $130 I expected a bit more. The receiver seems like a well thought out kit and went together very smoothly. It passed initial tests as outlined in the manual. There is a review of this kit here.

After spending a day evaluating the unit, I’ve been forced to conclude as supplied it is a marginally useful instrument for my application. I thoroughly checked out 16 poles that were very RF-noisy, but could only hear something from 3 of them with the ultrasonic unit. Two were just barely detectable while the third produced a good strong ultrasonic signal. Is the unit not sensitive enough for this use? Or are most of my line noise problems caused by sparking inside a device such as a lightning arrestor, which doesn’t permit ultrasound to escape? I have no way of knowing for certain.

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