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American Radio Library has uploaded new issues of the British Post Office Engineering Journal. Why did the GPO have an engineering research facility? Because the GPO managed ALL communication in Britain. It was like Post Office plus Western Union plus Bell Tel plus FCC.
This is the first in a long line of BBC television detector vans, enforcing the British policy of financing BBC with receiver license fees. It bears a remarkable resemblance to the Kraut Peilempfänger truck. [So I was able to modify the Kraut truck easily.]
According to the article (which is short on electronic detail) the receiver was not picking up the superhet IF oscillator. It was picking up the audio-frequency radiation from the horizontal sync coils.
This freq was certainly radiated from antennas. When TV antennas were common, and when my ears were younger and sharper, I could hear the 15750 cycles turned into acoustic form by electrostriction.
Here’s another view:
Our pet alien feels perfectly safe here despite the allegedly intense magnetic activity in the truck. Why?
According to a recent Daily Mail article, the Detector Vans have always been fake.
First, it’s nearly impossible to sort out the signals in a crowded city environment where each building may have a hundred residents.
Second, all the horizontal sync coils are on the same frequency, so it’s a much harder task than locating a spy transmitter or locating one superhet radio tuned to the WRONG freq.
Third, BBC never had more than a dozen vans for all of Britain, yet BBC has prosecuted thousands of unlicensed sets every year. The vans just cruise around to scare the yobs. The real license cops find scofflaws the lo-tech way by comparing a residence list against a license list, and then double check by knocking on the door and listening for BBC programs with their Mark I Eardrums. Sometimes the license cops pose as salesmen to get into the house and look around.
So our charge-based life form can rest over this van. No electronic activity inside it, and the residents have heard that the van will be working their neighborhood, so they have turned off all their electronics. The van is a Mobile Quiet Zone.