[ARC5] VHF, HF, and LF ARC-5s in one installation

[Mike Morrow]

Wayne wrote:

>It says that the airplanes have an R-23/ARC-5, an R-28/ARC-5, a T-19/ARC-5,
and a T-23/ARC-5.

That would be a "ferry" configuration which allows the R-23 to provide reception
of civil aviation tower frequencies (the standard one was 278 kHz), and transmission
on the standard civil aviation aircraft transmission frequency of 3105 kHz.

But this would not be the installation for tactical missions.  The the first two AN/ARC-5
manuals below contain system diagrams for single-place fighters installations.  Obviously
not all such aircraft would have been so equiped, but it's a good bet that many were
similar.

(1) NavAER 08-5Q-95   Handbook of OPERATING INSTRUCTIONS 
(2) AN 16-30ARC5-2     Handbook of MAINTENANCE INSTRUCTIONS, Vol. 1 LF MF HF Components
(3) AN 08-10-195        Handbook of MAINTENANCE INSTRUCTIONS, Vol. 2 VHF Components

The system consists of three receivers in a MT-65/ARC-5 rack, controlled by the
C-38/ARC-5:
(1)  R-4/ARR-2     246 MHz Homing Receiver (ZB-type system)
(2)  R-26/ARC-5   3 to 6 MHz Lock-Tuned HF Communications Receiver
      (or R-25 or R-27, matching transmitter below)
(3)  R-28/ARC-5   100 to 156 MHz Four-Channel VHF Communications Receiver

It also consists of two transmitters in a MT-71/ARC-5 rack, controlled by the
C-30A/ARC-5:
(1)  T-20/ARC-5  4 to 5.3 MHz HF Communications Transmitter
      (or T-18 or T-19 or T-21 or T-22, matching receiver above)
(2)  T-23/ARC-5  100 to 156 MHz Four-Channel VHF Communications Transmitter

Of course, the MD-7/ARC-5 and RE-2/ARC-5 would be part also.

This three-receiver, two transmitter installation thus provides the PTO essential
ZB-type VHF homing system, four channels of VHF communications, and one channel
of MF/HF communications.  That was quite a lot of capability in a small package.

Controls were also simplified.  Except for the R-4 homing receiver, only audio volume
could be controlled from the C-38 receiver control box.  Receivers were set for voice
only, and the MF/HF communication receiver would have been lock-tuned before flight.
Either of the two transmitters could be selected from the C-30A transmitter control box.
Transmitters were set for voice only.  The four VHF channel selector switch on the C-30A
selected the channel for both the T-23 and the R-28.

>So the pilot could select ""HF" or "VHF" on the control boxes and then be able to talk on
>5 VHF channels or one HF channel and could receive and tune the LF receiver as well.

The components you describe do not include a MF/HF receiver.  Your system is actually
four VHF channels, and one civil aviation 278/3105 kHz channel.

The system I describe could have a ferry mode setup, by replacing the R-26 with a R-23
and the T-20 with a T-19.  The R-23 would not be locked tuned, so a C-26/ARC-5 single
receiver remote tuning box (or C-125/ARC-5 panel) would have to be installed also to
support that.

In the Pacific Theater (PTO), the R-23 beacon band receiver would have been of little
value, compared to the 246 MHz VHF homing system.   R-23 units would not have been
required for tactical installations.

>I had never thought of using a mixture of ARC-5 VHF, HF, and LF radios in a fighter but
>this makes a lot of sense.  It must have been a fairly late war development, because the
>manual says that it replaced the one from June 1944.  I never heard of the USAAF doing this.

Most of the AN/ARC-5 components seem to have appeared very early in 1944.  The system I
describe should have been flying by early 1944.  If one examines the data for the MF/HF
frequencies most often used in the PTO, its seems that the R-26 would have been the most
frequently used HF receiver, and the T-20 the most frequently used HF transmitter.

The USAAF was, IMHO, quite a bit more advanced in the VHF command set area.  They had
the SCR-522-A by 1942 in the ETO.  It seems most ETO USAAF fighter aircraft had this VHF
command communications, along with something like a BC-1206 if beacon band coverage
in the LF/MF band was desired.

Mike / KK5F