[Milsurplus] LO radiation

[Richard Brunner]

Rob wrote:
> The Navy observed as soon as superhets came around that they had
> interference from one receiver to another aboard ship.  This is not
> surprising with receive antennas so close together and is a legitimate
> reason not to have receivers that leak LO radiation.  Enemy DF business
> speculation by outsiders to explain the Navy's specification?

There has been endless speculation on this point.  I have read German U-Boat 
logs looking for DF references, and found nothing, mostly comments on 
weather, etc.  I have corresponded with Germans, mostly retired commercial 
RO's, and they conclude they never routinely did it.  The Germans most 
certainly knew about receiver LO radiation, but concluded that one would 
have to be very close, within a few miles, to detect LO radiation, and then 
you could see the ship as well.  The subs also had underwater listen gear 
which could hear ship's screws 20 to perhaps 50 miles away, so they had no 
need for LO Df'ing.  Further, a guy with experience said you need a decent 
signal for DF'ing, and he often had trouble getting bearings on 10 Watt 
beacons more than a few miles away.  The latest theory is that the myth of 
LO radiation betraying ship locations was Allied disinformation hoping to 
mislead the Axis into believing we were sinking subs located by receiver 
radiation.

It wasn't only superhets.  I have seen records of ships being QRM'ed by 
regenerative receiver radiation from ships in the same vicinity.  Also in 
the 1920's RO's reported hearing regenerative receiver radiation as much as 
30 miles as sea.

Richard Brunner, AA1P