[Milsurplus] Question ( RBS; submarine )

[Hubert Miller]

I do have doubts about this.

As i posted some time back, an example of the fears of the time, passengers on a coastal run from Seattle to Alaska were forbidden to use electric razors

during the sailing, for the same reason. Who reported that, that it endangered the ship?

 

So the receiver on this lone merchant ship was one of the two or three tube things from the early 1930s. Detector and one or two steps of audio. In a 

regen receiver, you don’t use the efficient coupling to the antenna that a transmitter does. So even if the oscillating detector is at a few milliwatts, the

actual radiated is much less. 

Ship owners tended to leave working, antiquated equipment in place forever. I read somewhere that U.K merchant ships early in the war, had their

simple regens changed out to non ( or, less ) radiating receivers.  No references were provided for that statement. However considering the fear at the

time, such putative incident would have to be in the early part of the war, before measures were taken.  Night to day propagation varies also and may 

complicate the question of how practical this was. 

 

Then, what kind of receiver were the German raiders using? It had to be something off the shelf of their own standard equipment. When you look at the

“LOWFER” DX records, don’t equate modern high selectivity receivers with what was available in 1940 in DF equipment.

Of course the raider listened on 500 kHz, as did everyone, probably particularly for “SSS” signals – “submarine sighted” reports.

 

It occurred to me that daylong listening carefully for weak carriers on 500 kHz would be the absolute dullest job in the world.

-H M

 

 

>"It has been reported", .... but I don't know where -

>From http://www.tubedevices.net/Lorenz.php
"It has been reported that a German raider during WWII indeed managed to locate merchant ships sailing on their own, not in convoy, by direction finding on the signal radiated by their receivers. Presumably, these ships had rather old-fashioned equipment, perhaps with an oscillating detector directly coupled to the antenna."

Certainly NRL and USN training documents say that the purpose of shielding and RF and stages was to prevent LO radiation that could be tracked by enemy ships. The NRL history states this rationale for the RAA, RAK, RAL, etc. designs, well before it could have been invented as a "cover story" for Ultra, etc. So it seems there was certainly the belief that it was possible.

I'm not so hot to dismiss this as myth or misdirection - The middle of the Atlantic in 1942 must have been pretty damn quiet RF-wise. (Unimaginably quiet compared to my house.)  And an oscillator connected to a nice long wire high above a steel ship in a salt water ocean is not to be sneezed at.

Current QRP efforts have shown 500+ mile reception on 80m with a 40 microwatt transmitter. 
Here's some 100mw 500kc results - http://www.w4dex.com/medfer.htm




Nick England K4NYW

www.navy-radio.com <http://www.navy-radio.com> 

 

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