[ARC5] R-4

[Bob Macklin]

So what's wrong with operating these on the 1.25M band? We tore a lot of
these units up for parts in the late 50s, early 80s.

I was in the USAF and we did not know what they were used for. But we did
know they were some kind of beacon receiver.

Bob Macklin
K5MYJ/7
Seattle, Wa.

"REAL RADIOS GLOW IN THE DARK"

----- Original Message ----- 
From: "Mike Morrow" <kk5f at earthlink.net>
To: <w8fdv at aol.com>; <ARC5 at mailman.qth.net>
Sent: Wednesday, March 30, 2005 3:06 PM
Subject: Re: [ARC5] R-4


> w8fdv asked:
>
> > What is an R-4?
>
> I'm assuming that you mean R-4(*)/ARR-2.
>
> It's the airborne part of a WWII and 1950s USN aircraft homing system.
>
> The system operated from 234 to 258 mcs (typically 246 mc), and a typical
aircraft carrier or base transmitter system might have been a "YG."  The YG
had a narrow beam rotating antenna system and transmitted a different Morse
character depending on which way the antenna was oriented and the ship was
headed.  The pilot had decode cards which told him which true radial he was
on for the code character he was receiving.
>
> The cute thing about this system is that the transmitted 246 mcs signal
was modulated at one of six different frequencies in the AM broadcast band
(from 540 to 1030 kc).  Assuming that the modulation channel selected was
830 kc, the TRF front end and grid-leak detector demodulated the 830 kc
modulation on the 246 mc signal, then the second half of the receiver
detected the 830 kc signal and its BFO produced a Morse beat note as the 830
kc modulating signal was keyed at the transmitter.  Voice ID and other info
could also be transmitted.  An enemy that intercepted the the 246 mc signal
could hear nothing of the 840 kc signal in his headphones.
>
> Dial calibration marks leave off the "2" so you'll actually see "46"
rather than "246."
>
> The AN/ARR-2 replaced the earlier ZB-series and R-1/ARR-1 homing adapters
which were just a front end which fed into a separate receiver tuned to the
appropriate modulating frequency in the broadcast band (RU, RAX, ARB,
R-24/ARC-5, BC-946 for USAAF, etc.).
>
> It's a neat system, developed before WWII.  Most of the early ZB-series
units actually show all three digits on the tuning dial.
>
> On the R-4/ARR-2, the small tuning dial on the lower left corner sets the
front end frequency, and the tuning spline control changes a number 1 to 6
in the window to set the second part of the receiver to one of the six
modulating frequencies.
>
> The receiver is designed to fit into an ARC-5 receiver rack.  A late-war
Navy single-place fighter might typically have had an R-4/ARR-2 homing
receiver, a fixed-tuned R-26/ARC-5 HF communications receiver, and a
R-28/ARC-5 four-channel VHF communcations receiver in the fighter's
three-receiver ARC-5 command radio rack.  The control boxes for the
communications gear in that system would be a C-30A and C-38/ARC-5.  The
C-38/ARC-5 has all the controls needed for the R-4/ARR-2.  I think of this
system as sort of an early example of integrated avionics.
>
> I have AN/ARR-2 manuals whose revision dates indicate that the system was
used into the mid-1950s.
>
> These sets are pretty useless outside their original application, but they
represent a lot of history.  Hacking one is discouraged!
>
> 73,
> Mike / KK5F
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