[Milsurplus] 24 Volt BC-312's & KC-97L

[James C Whartenby]

The installation may be implausible but it evidently exists.  We will
have to wait for the report on a revisit to the aircraft to see if it is
as remembered.

I am not familiar with the R-348/ARR-36.  Never been up close and
personal with one.  Since it was designed for use with an auto tuned AM
system, it is also auto tuned, set and forget.  As you hint at, this is
great for fixed frequency operation but makes searching for a signal
difficult.  Since this aircraft was from the ANG, finding a proper ARR-36
might have been difficult, at the very least.  You also mention that not
all ARC-21 installations had the ARR-36, so the need for a tunable
receiver may have existed in this installation.  The one chosen was the
one that was available.

The ARC-21 was the first HF aircraft auto tuned transceiver, as far as I
am aware.  Might even be the first to use mechanical filters, two in
fact.  As you said, it and the later ARC-38 were both designed as AM
systems and were later retrofitted to be SSB compatible.  That makes them
both interesting to me.  As for reliability of the ARC-21, I am unaware
of any new system being fully functional and long term compliant,
especially the first of a new series of radios.  It seems to me that
every communication system has gone through the modification process to
correct problems later identified in the field.  With the dramatic change
from AM to SSB in the mid 1950s, it was most likely more cost effective
to develop a completely new SSB system from the ground up instead of
going through several rounds of system modifications and updates.
Regards,
Jim

On Tue, 17 May 2005 08:53:54 -0700 (PDT) Mike Morrow <kk5f at earthlink.net>
writes:
> Jim wrote:
> 
> >The lower frequency IF of the BC-312 would make it more frequency
> >selective then the BC-348 for starters.  I was surprised at how 
> well the
> >BC-342 that I have up and running, performs receiving SSB.
> 
> The would have been no need for a BC-312, or even a BC-348.  The 
> R-348/ARR-36 HF auxilary receiver was specifically designed for use 
> along side the AN/ARC-21 and AN/ARC-65 systems.  It tunes exactly 
> the same frequency range and increments as the AN/ARC-21/65.  The 
> R-348 (not BC-348!) is quite an elaborate all subminiature vacuum 
> tube design whose control box is identical to the AN/ARC-21's 
> control box.
> 
> >I agree it is a strange installation.
> 
> It is a completely implausible installation, IMHO.  
> 
> >other receivers, like the Navy ARR-41 may have been more 
> appropriate
> >but not available?
> 
> No need...the USAF had the AN/ARR-36.
> 
> The Navy's equivalent to the RCA AN/ARC-21 was the Collins 
> AN/ARC-38.  And just as most AM AN/ARC-21 units were modified to 
> become the USB capable AN/ARC-65, the AM AN/ARC-38 was modified (by 
> RCA!) to become the USB capable AN/ARC-38A.  Also, just as the 
> AN/ARC-21/65 had the dedicated HF auxiliary receiver AN/ARR-36, the 
> AN/ARC-38/38A had the dedicated HF auxiliary receiver AN/ARR-41.
> 
> Some sidetracking follows:
>  The information I have seems 
> to indicate that while many USAF AN/ARC-21/65 installations did not 
> include the AN/ARR-36, almost all the USN AN/ARC-38 installations 
> included the AN/ARR-41. 
> 
> 73,
> Mike / KK5F