Y-Gerät

[Panrock]

I stumbled across this unusually detailed account of the attempts to derail the German Y-Gerät aircraft navigation system, using transmissions from Alexandra Palace during WWII. Apparently it was the television sound transmitter that was re-tuned and used, and a television set rustled up for monitoring purposes.

Go to page 8. 
https://www.bbceng.info/Eng_Inf/eng-inf-...gInf51.pdf

Steve

[ppppenguin]

Thank you. Excellent account, better than anything I've ever seen before. I'd mistakenly always though they used the vision TX. Complete with wonderful cartoons by "Paff". Some interesting comments here. I note one of the references in the article is to the superb book "Most Secret War" by RV Jones. If you don't have a copy then you're missing something really good.

More about Paff, who died aged 102, here: https://www.imperial.ac.uk/alumni/alumni...30---1939/

[peter scott]

Like Jeffrey this is the first time I've seen this excellent write-up. I still don't fully understand the process but definitely another step on the way.

Many thanks for posting Steve.

Peter

[Panrock]

Judging from the pictures present on Peter's site and other places, there seems to have been a 'duty 702' (Marconi) television set in use for monitoring, at AP pre-war. Presumably this was the mirror-lid set referred to in the article and was switched on during the war. It looks soooo like the example I used to own, but that's wishful thinking. I don't suppose we'll ever know its serial number.

Steve

[peter scott]

Site now updated thanks to your information Steve.

Unless you or the BBC reveneered the set I don't think your 702 was the one from EMI control room.

   

Peter

[ppppenguin]

If I remember correctly from Jones' book, they didn't actually receive and re-radiate. They just jammed and that was enough.

[Panrock]

Peter, well I had no idea you had that photo! Thanks for setting my fantasy to rest.    Also, there's a ding on the AP set. Mine originally had a ding too before I restored it, but in a different position. So it's "Game, Set and (Book)match" to you! But could it have been Jeffrey's set..?

Jeffrey, I'm going to have to set aside the time to read this article properly, so that I really understand it. Currently I don't.

Steve

[ppppenguin]

Dr Plendl and the other German signals people must have had a blind spot when they chose the frequencies for Y-Gerat. Nicely in band for the most powerful TX in Europe hence an easy target for jamming.

Before Y-Gerat our scientists and engineers had already countered Knickebein and X-Gerat. These were technically simpler systems. On our side we had Gee and Oboe as aids to finding bombing targets. Again I recommend Jones' book for a good overview of radio navigation and much else to do with science in WW2.

[peter scott]

But could it have been Jeffrey's set..?

Steve

No, Jeffrey's set has yet again different veneers. If we had a higher quality image of the 702 used at Radiolympia then we could check for "finger prints" there too.

Peter

   

[Panrock]

I've had another read of the article and it seems the 42 MHz transmissions from Cassel, France were re-radiated from AP, causing a 'howl-round' effect. Besides this, various weaker signals at 43.5 and 45.0 MHz were present. So if you'd turned on your television set at certain times in late 1940 and early 1941 you'd have been greeted with 300 Hz or 3000 Hz bars on the screen... the clear and sharp ones coming from the AP transmission. Maybe the field timebase would have locked to them , rendering them stationary. But then also you'd have received the 'howlround' too... more bars and intense picture fluttering??  Depending on the alignment and sound tuner setting on your set, any audio tones  accompanying would probably have been weak.

The 'Duty 702' at AP couldn't have been very sensitive once its strip had been realigned to cover between 40 and 50 MHz.

Any mistakes in the above account, please let's hear them.  This is an interesting niche in television history.

Steve