[ARC5] British WWII Avionics

[Sandy]

Amateur conversion of the SCR-522 were popular before the advent of the 
Gonset Communicator.   The BC-624's used the somewhat "dull" 9003 pentodes 
instead of the later 6AK5's.  These could be substituted and it picked the 
sensitivity up quite a bit.  The set had some very good points in spite of 
it's vintage.  What "MADE" the BC-624 and hopped up the BC-639 receiver was 
the advent of the 6BQ7 cascode dual triode preamplifier.  It quickly drive 
the old 6AK5 into oblivion as a decent RF stage capable of a decent noise 
figure.

There was nothing that could be done on improving the transmitter section of 
the '522.  Some of the locals added things like the Millen design 829B 
amplifier for more RF output.  Later the AX9903/5894 dual tetrode became 
very popular on 2 meter AM.

One amateur who owned a construction company (Bill Kelly W5MXJ) converted 
quite a few SCR-522's and used them for communications in his construction 
equipment and trucks instead of spending big bucks on the double bucket 
Motorola FM stuff.  Bill was an inveterate tinkerer with VHF gear in his 
amateur career.

73
Sandy W5TVW

-----Original Message----- 
From: J. Forster
Sent: Saturday, July 07, 2012 9:28 PM
To: Robert Eleazer
Cc: arc5 at mailman.qth.net
Subject: Re: [ARC5] British WWII Avionics

> I note that all of the SCR-522 sets have both U.S. and British nametags.
> I wonder if any other equipment had that feature?

Some BC-929's were double badged, and I've seen at least one with an added
RAF nameplate. I suspect some APN-4 LORAN-A sets were also.

> The 522 must not have been too horrible, because it appears that the
> receiver formed the basis for the BC-639 ground radio, which of course
> dispensed with that bizarre crystal tuning scheme.
>
> I read that the British invented microwave airborne radar and bought it
> to the U.S.

I believe it was more the Microwave Magnetron. A sample was brought to the
US on the Tizzard Mission.

> They thought the Americans were boastful when they described
> their enthusiasm for the new technology and how they would use it.

The British magnetron was hogged out of a solid copper block. Copper is
hard to machine, because it is soft and tears badly.

The sample was shown to Percy Spencer of Raytheon and he worked out how to
mass produce the thing by furnace brazing a stack of punched out plates,
interspaced with solder preforms. Maggies made this way could be made in
numbers that staggered the British, and because the cavity strapping was
better, produced a lot more power.


> But a month after the British introduced the U.S. to the radar
> technology the U.S. knew as much as the British and had designed their
> own version of the set, with a better receiver.

The MIT Rad Lab was set up to do that kind of thing...  from concept to
working model very quickly. Companies like Raytheon followed a half step
behind.

> A month after that the new factory to build
> the sets was completed.  And a month after that the set was in full
> production.  The British were astonished.  The Americans were not
> bragging but simply stating facts.

R&D and the vast US industrial base was capable of very fast quantity
production. Remember, much of the surplus we are playing with still was
built in under 4 years.

> The British quit building the sets and just bought them from the U.S..
> They eventually started building some of their own later, just so they
> would not forget how.

The US had big advantages, including about ten times the population, vast
natural resources, and a huge industrial base. It was also not under siege
and at the end of a long, U Boat threatened, supply chain.

> I think the same thing happened with the SCR-522.
>
> As for British bomber radios, I would guess they had no need for a
> "command set."  The RAF heavy bombers did little daylight formation
> flying until the latter part of 1944, when the USAAF had pretty well
> cleaned up the Luftwaffe relative to the shorter range missions, such as
> to France.

The RAF did a lot of night-time bombing, guided by the Pathfinders.

> I wonder if the B-17's, B-24's and B-25's the British operated used U.S.
> or British radios?

Almost certainly US radios, I'd think.

-John

==================
>
> Wayne


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