[ARC5] Re: VHF SCR-274-N

[Mike Hanz]

I can find only two documents describing the VHF -274N/ARC-5 - "A 
History of Engineering and Science in the Bell System", and the Signal 
Corps History of WWII.  Bell Labs takes credit for the VHF ARC-5 
development (which explains why most of the sets I've seen have CW as 
the manufacturer), though the 274N and ARC-5 set development is sorta 
smushed together in a way that isn't precisely conclusive: 

"Just before Pearl Harbor day, it [Signal Corps] requested development 
of radio equipment that would add a line-of-sight VHF capability to the 
high-frequency, long range SCR-274 system developed earlier.  This new 
VHF equipment, coded the AN/ARC-5 radio set, originally specified 
operation on preset frequencies in three VHF frequency bands.  This 
arrangement was modified during development to correspond with state of 
the art progress in obtaining improved performance from receiver and 
transmitter vacuum tubes and circuits at these very high frequencies.  
The development was eventually expanded to provide operation over the 
full 100- to 150-MHz  band. the improved equipment included a narrow 
receiver bandwidth (which would reduce interference and increase the 
number of usable channels), remote selection of ten [sic] channels, and 
quartz crystal frequency control for both the receiver and transmitter.  
Over 35,000 of these radio sets were built and delivered from 1943 
through V-J Day in 1945."

Whole lotta development goin' on there... :-)

The transition between the old and "new, improved" set may be the 
breakpoint for the SCR-274N to ARC-5 conversion, but that's just 
speculation.

A couple of related clips (hopefully with enough context) from the 
Signal Corps history in the 'US Army in WWII' triplet of books:

"Nearly a year earlier [apparently June 1941], when the Air Corps first 
began pressing the Signal Corps to adopt in toto the British VHF system, 
including the VHF crystal controlled command set [referring to the 
SCR-522], Lt. Col. Harry Reichelderfer had spoken up for the American 
SCR-274.  The ARL [Aircraft Radio Laboratory], he pointed out, already 
had a project underway to provide VHF components which could be used 
interchangeably with the 274."

and

"The Air Force hoped to convert it [the 274N] to VHF operation and in 
June 1941 had asked that the Aircraft Radio Laboratory develop a VHF 
component for it.  The laboratory's engineers were drawing up the 
specifications by mid-1942."

What seems somewhat strange is that the ultimately revised VHF ARC-5 set 
was apparently purchased more by the Navy than the AAF, this despite 
their having two other VHF sets in the inventory.

73,
Mike

WA5CAB at cs.com wrote:

>Well, no one seems to have any docs related, or at least they haven't piped 
>up, but I'm more inclined to surmise that much the same thing happened as 
>apparently happened with the ARA-1/ATA-1.  The project was rolled over into the new 
>AN/ARC-5.  Even to the extent that some of at least the BC-950's were either 
>converted to or finished as T-23's.  I've had several of those.
>
>In a message dated 4/6/2008 6:17:31 PM Central Daylight Time, 
>kk5f at earthlink.net writes: 
>
>>Robert wrote:
>>
>>>Au contraire.  Someone accepted some at least long enough for them to get 
>>>orange QA stamps and then surplussed out.
>>>
>>That would happen to trial-use units too.  I've seen it speculated that less 
>>than 1000 VHF SCR-274-N sets were fielded (certainly only a very limited 
>>trial) before they were abandoned.  As this was during WWII with its voracious 
>>need of VHF gear, that spells "reject" and "not accepted as standard" to me!
>>