[ARC5] AN/ARC-3

[Mike Morrow]

Ken wrote:

>I have essentially two each ARC-3 TX and RX, but nothing else. I understand 
>the ARC-3 was used in a number of late WWII fighters. Is this true? Which? 
>Someone once mentioned the P-38 and F6F....

The AN/ARC-3 was a USAAF set that replaced the SCR-522-A.  Beginning late
in WWII, continuing well into the 1950s, the AN/ARC-3 was the main VHF
command set used by the USAAF/USAF.  It would have been found on *every*
type of USAF aircraft of that vintage (bombers, fighters, transport, etc.).
The pilot's manuals for most USAAF aircraft of the late WWII era will
provide details depending on if the SCR-522-A is installed, or the AN/ARC-3.
For example, a manual for the P-61 Black Widow says there will be either
one AN/ARC-3 8-channel set or two SCR-522-A 4-channel sets on board.

At the USAF Museum in Dayton, OH, there's a B-50 (IIRC) fuselage that
you can walk through.  The remnants of an AN/ARC-3 will be seen there
too.

The F6F, or any other type of Navy aircraft (unless the USN had taken over
some former USAF aircraft), would NOT have used the AN/ARC-3.  If a VHF
set was used at all, it would have been one of the USN VHF sets (AN/ARC-4,
VHF AN/ARC-5, or AN/ARC-1.  The USN did borrow a few SCR-522-A VHF sets
from the USAAF.)

>What amazes me about them is their later models (ARC-36 and 49) with 
>many more channels. Apparently it wasn't all that hard to add them.

The AN/ARC-36 used an add-on structure at the front of the radios to
double the channels to 16.  The normal 8-channel AN/ARC-3 control was
used, with an external switch to select the desired bank of eight.
The frequencies in the second bank had to be selected such that they
used the same receiver local oscillator harmonic that was dialed
into the receiver for that channel for the other bank's frequency.
The 48-channel AN/ARC-49 was considerably more complex, and used the
C-1400/ARC-49 control box that selected the desired channel.  The
AN/ARC-49 normally came out of the box with 48 standard channels
already filled and aligned with the appropriate crystals.

The USAF seems to have wanted to keep most of its aircraft in possession
of VHF-AM capability, even after UHF-AM took over military command
comms.  The most common replacement for the AN/ARC-3/36/49 in the
early 1960s was the VHF Collins AN/ARC-73.  The most common UHF-AM
command set of the 1950s on into the 1970s was the famous Collins
AN/ARC-27 that was used by all services almost everywhere, but USAF
aircraft often kept VHF-AM capability along side it.

A good representation of an early 1950s USAF aircraft radio installation
would include the AN/ARC-3 VHF-AM, AN/ARC-8 MF/HF, and the AN/ARC-27
UHF-AM sets.

The USN usually replaced VHF-AM with UHF-AM and discarded along-side
VHF-AM command capability.  The first somewhat common UHF-AM set was
the USN's RT-58/ARC-12.  Its claim to fame was that any AN/ARC-1 VHF
installation could be converted to UHF simply by pulling the RT-18/ARC-1
VHF unit out of the mounting rack, sliding the RT-58/ARC-12 UHF unit
into the AN/ARC-1 rack, and possibly changing the VHF antenna with one
designed for UHF.  Nothing else needed to be altered.

Mike / KK5F