[Milsurplus] ARC-5 and the ARRL

[C.Whitaker]

Breck, and all.
The Command sets did go on.
They were in the MPN-1 GCA up until the CPN-4 came out.
They were in the C-47's, and other airplanes of that area, that
I thumbed a ride on.  The crew used them, but the radio operator,
(if here was one), used a BC-375, or an ART-13 later on.
Maybe not a lot of people know this, but there was a test and
adjustment kit for the command sets.  The components
emulated the boxes and cables in an aircraft, and had slide-in
mini-racks for the equipment being repaired.  One item was
a dummy load.  All that was needed was a work bench to
mount everything on, and a DC power supply.
I don't know if they were common in a Base Radio Shop, but
ours came with our MPN-1 that had come into France during
the WW II invasion, and then it was moved to Berlin.
The MPN-1 had a few different search antennas designed
for it before it was retired..
Some trivia for you Techies, but the precision radar in the
MPN-1 was not all that stable, and the design engineers found
that the frequency could be pulled by the mismatch between the
antenna switcher, (between Vertical and Horizontal), and the
magnetron.  The magnetron would fire for a short time, and
the pulse length was long enough for the reflected wave to
return to the magnetron before it had stopped firing.  This
caused the magnetron to wiggle off frequency.
Good ol' American Ingenuity stepped in, and the engineers
extended the wave guide, (folded up behind the Horizontal
antenna, and called a Trombone), until the pulse travel time
was much longer, and the reflected pulse, due to the mismatch,
didn't arrive back at the magnetron until the magnetron had
ended its firing.  It's in the book.
Happy St Pat's Day everyone.
As Brendan said, "If it weren't for Barley Bree, the Irish would
rule the world."
73  EOT
Clete
++++++++++++++++++++++++++++++++++++++++

On 3/16/2013 3:08 PM, B. Smith wrote:
> On 3/16/2013 1:39 PM, Ray Fantini wrote:
> April issue, ????? Might be a joke,
>
> Actually "Command sets" were still installed in  a lot of aircraft 
> well into the 1950's and low frequency units were used well into the 
> 1970s. So I guess they went
> "somewhere" and were utilized  quite a bit  for the HF tower 
> frequencies and often was the primary equipment installed for airways 
> navigation. In other countries they were regarded as primary 
> equipment, so the Command Set carried on after WWII.
>
>
> Z
>
>
>
>
>
>
>
>> April issue of QST, page 80 bottom left corner And on the ARRL web 
>> page promoting Field Day is a retro looking graphic promoting Field 
>> Day 2013 and close examination of the graphic will reveal a Command 
>> set or ARC-5 style transmitter and receiver. Another example of how a 
>> radio that went nowhere in military or civil aviation after the war 
>> went on to serve and find extensive use and modification  in the Ham 
>> world, so much so that today when developing a graphic for showing 
>> “old time” ham radio it makes the cut  where commercial Ham products 
>> of that generation did not. The greatest significance and 
>> contribution of the ARC-5/SCR-274 family of radios may be in the use, 
>> modification and long lived realm of Ham radio, way beyond there 
>> service record in WW2
>> This is a statement of my opinion, and not intended to persuade or 
>> influence others but I am posting this in my never ending battle to 
>> justify the legitimacy of preserving and in some case building the 
>> Ham modified military  radio as being just as significant as the 
>> preserved copies of the radios that were in military service.
>>   Ray F
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