Frederick W. Chesson						ARB.HTM
144 Fiske Street,						Rev: 12-25-99
Waterbury, CT  06710			




                  A Classic Radio, the ARB Navy Aircraft Receiver 
                                       by    
                              Frederick W. Chesson 

   (Orginally appeared in August, 1990 Issue of "The Old Timer's Bulletin" 
			 of the Antique Wireless Asso.)
 
     We've grown old, or at least older, together, my ARB radio and me.  I was
still technically a teenager when I received it, Christmas Day, 1949.  On the 
26th, I would be all of twenty and starting my fifth year in the Electron Art.
     My ARB was a compromise between another Command Receiver, probably a BC-454
to match my BC-455 of two Yuletides ago, or a desirable but presently unafford- 
able BC-348.  The ARB, covering 195 through 9050 Kc in four bands, also had one
feature absent from the 348, a Standard Broadcast Band.
     My set, from Arrow Sales in Chicago, was a well-used veteran, if not of  
combat, then of the repair bench.  Both fuse and spare were gone from the front 
panel and the dynamotor leads hung slack. But, not to worry, the dynamotor is 
to be ousted anyway by a power transformer.  So unleash the diagonal cutters, 
and let the Great Conversion begin...! 
     This I did, thanks to R. E. Goodheart Enterprises of Los Angeles, which 
published a variety of schematics and conversion plans. So, by January, 1950's
end, my ARB was ensconced on my bed-side table. There, except for a college 
sojourn, it has been in daily usage ever since, tuned mainly to WOR or WCBS for
the first news of the day or the last word at night.
     Over the years, its short and long wave bands brought the world to my ears.
Sometimes the Cold War news became all-too warm, as during a certain rainy week-
end night in June, 1950, when the first hints of the Korean War's opening came
from the eight-inch speaker housed under the bed in an old RCA R-100 enclosure.
During that conflict some ARC-274Ns and ARBs were still airborne in a world of
AN/ARC-5s and ARR-71s.
     Or again, in the Hungarian Uprising of October, 1956, when I listened to 
the UN's largely futile protestations, or in another October, six years later,
when the rumblings of the Cuban Missile Crisis began to spread across the bands.
There were minor repairs in the course of time, but mostly it's been a long and
happy association with ARB No. 12,266....

				  VITAL DETAILS

     For the purist, ARB stood for the overall equipment package, just as 
SCR-274N was the Signal Corps designation for the receiver-transmitter group 
(SCR = Set, Complete Radio) of which the BC-453 family was a part (BC = Basic 
Component).  The receiver, according to its engraved nameplate, was actually 
CRV-46457, the CRV standing for RCA in the military's wartime nomenclature 
system.  My set's Serial number was a rather low 12,266. Its weight, of 26.8
pounds also stamped into the nameplate.  For some reason, no doubt in the
interests of National Security, the Contract date had been defaced.  But since 
these determined measures did not extend to new, still-boxed, equipment, it was
no great feat to determine the mystery date as February 23, 1942.  The Contract
Number, NOs-98559, was left intact, as was Camden, New Jersey, the place of its
manufacture.  The first manual for the ARB was IB-38142, issued in February, 
1942, and followed a year later by NAVAER 08-5Q-3.
     Manufacture at RCA's Indianapolis, Indiana plant was indicated by an "I"
prefix of the serial number.  This was part of a realistic, if fortunately un-
necessary, dispersal plan, to relocate critical industries away from vulnerable
costal locales.  At any event, a total of some 30,000 sets were made, enough for
a quarter of all Navy aircraft, making the ARB one of the more common, and 
affordable, receivers on the Post War surplus scene.
     In the heady surplus era of 1947-49, the set was almost as common as the 
ubiquitous SCR-274N, and often available for around ten dollars, used.  They 
were almost as long-lived on the market, as well, with Fair Radio Sales of Lima,
Ohio advertising them well into the 1960s.  Brand new control boxes were still
being offered even as late as 1985. 
     The ATB Transmitter companion of the ARB was almost NEVER seen, however,
on the market.  Its range was 3.2 to 9 MHz, via two plug-in tuning units.  
Optimum power output was 25 watts CW and 20 watts voice.  This may have been 
the set's major shortcoming, as its DC input power requirements were 12 amperes
at 28 volts, close to 360 watts!  One legend has it that, in order to achieve 
stability over its tuning range, the set's output had to be drastically reduced.
     Photos show the ATB to be a masterpiece of complexity, with elegant panel
controls and neat little pull-out calibration charts in each tuning unit. 
Only 4,000 were reported made, accounting for its scarcity, and the familiar 
Collins ART-13 "Auto-tune" soon replaced it in aircraft use.
     According to an RCA internal publication on its World War II contributions,
the ARB receiver and ATB transmitters were the outgrowth of earlier civilian 
aircraft models called ARV-50 and ATV-50, respectively.
     The ARB has two control boxes, a dual-control version for the Operator,
with the designation CRV-23256, and a simpler one for the Pilot, type CRV-23254.
     The Operator's Control Box has a Local-Remote change-over switch, which
could be over-ridden by the Pilot, via a flexible-cable linkage.  The band 
switch is divided into two modes, HOMING, with 195-560 and 560-1600 Kcs Bands 
and COMMUNications, with the above two bands, plus 1.6-4.5 and 4.5-9.05
Mcs.  The function switch has five positions.  OFF, C.W.,  M.C.W., SHARP, BROAD.
A mechanical interlocking system limits HOMING functions to C.W. and M.C.W.
(continuous wave, straight code, and modulated continuous wave or code sent with
a built-in tone, so that no BFO was needed).  In addition, the BROAD mode of
reception, typically AM voice, can not be employed on the lowest 195-560 band.
     Both boxes have the above band and function switches, plus an INCREASE
OUTPUT volume control and two headphone jacks.  The audio system of the ARB is
rather complex, the OUTPUT control being a three-decker pot, fed by 600 and 4000
ohm taps on the output transformer.  According to the Operator's Instruction 
Manual, this was to prevent "blasting" in the user's headphones when going from
AVC to manual gain functions.

     Circuit-wise, the ARB is relatively simple, taking advantage of its four
muti-function 12SF7 diode-pentode tubes.  A block-diagram is shown in Figure....
A 12SF7 RF amplifier is followed by a 12SA7 converter and two more 12SF7s as IF
amplifiers.  Another 12SF7 does duty as BFO.  A 12A6 beam-tube, common also to
the SCR-274N and ARC-5 Command Receivers, follows as AF output.  The diodes in
the last two 12SF7s are used for audio and AVC detectors, respectively.  A 955
neon tube regulator is used in the mixer stage, but its removal does not seem 
to seriously affect tuning stability.
     Two IF frequencies are employed, adding a bit of circuit complexity.  135
KHz is used for the two lower bands, and 915 KHz for the upper bands. The BROAD-
SHARP function is brought into play by a relay shunting resistors to ground in
extra windings on the first two IF transformer's secondary windings.  This is 
only available on the two upper bands.
 
     HOMING refers to the secret ZB navigational aid for enabling carrier air-
craft to home in with less risk to the ship than by open transmissions.  In this
system, an audio signal modulated an RF carrier in the lower two bands of the 
ARB's range, say at 1000 Kcs.  This, in turn, was then used to modulate a UHF 
transmission in the 234-258 MHz range.  While the enemy might easily detect the
UHF signal, its modulation, being at an RF frequency, would not be so readily 
detectable.  In addition, coded signals, representing the homing quadrants, were
changed daily.  A long, narrow converter, the ARR-1, using 954 pentode acorn
tubes and permeability tuned, was clamped to the top of the ARB, receiving its
B+ and heater voltage from a connector on the top-left front panel. The RF out-
put was fed through a relay box to the ARB's FIXED Antenna post.  A loop-antenna
direction finder, the DU-1, was connected to the L1 and L2 antenna posts and 
thnce through a change-over relay, operated by the control box.  Normally, a 
trailing antenna, wound on a motorized reel was used for the upper two bands, 
and usually for the transmitter as well, through a another change-over switch. 
The ARR-1 Converter was later replaced by a complete receiver, the ARR-2.

			    Conversion Information. 

        The fortunate owner of a still-intact ARB receiver should seriously 
consider leaving it intact, as much as possible.  Compact, solid-state power 
supplies of 28 VDC are available for operation in the original dynamotor mode.
However, unlike the BC-348 and similar receivers, the ARB requires an external
control box and external tuning head.  The internal tuning dial has a lucite 
magnifying window, but its relatively tiny aperture seems intended more for the
convenience of servicing personnel, with the airborne operators relying on the
typical "coffee grinder" remote tuning units.
     Duplicating the control box functions is relatively simple, as the inter-
locked switches and complex audio level system can be dispensed with.  Band-
switching can be done via the front panel knob (counter-clockwise only, please)
and there is ample space for local controls once the band-change-motor switch 
and fuse-posts have been removed.  Removal of the two Cannon receptacles also 
gives mounting room for RF and AF gain-control pots.  Experience will soon show
what control modes are best used.  For the most part, the RF gain can be run 
wide open and the AF gain adjusted for listening level.
     The set also suffers from the lack of a variable BFO, which makes SSB re-
ception on the difficult side.  Running a 25K control to R137 can make for a
passable operation, but installing a varactor diode across L-110 is a better
overall solution, even though requiring a stable source of low-voltage DC.

     As mentioned at the start of this article, removal of the dynamotor leaves
plenty of room for a power transformer.  A unit having a secondary winding rated
at 500 V at 75 MA is adequate.  In the Author's conversion, the band-change 
motor was removed and its mounting frame modified to accept a 7Y4 rectifier.  
Later, silicon diodes were retrofitted. Unless period antiquity is required, 
a 5Y3 or 6X5 would be the vacuum tube of choice.  
     Without the remote tuning head, a spline and knob can be fitted directly to
the threaded shank of the gearbox, though this method is awkward; so as long as
extensive front panel modifications are being made, one should consider dispens-
ing with the worm-gear drive and going direct to a flush-mounted tuning knob.

				As You Were....

     In closing, we return again to another era, where the ARB apparently flew
in nearly every US Navy plane having a radio operator, and certain single-place
aircraft, as well.  Such craft included the multi-engined PBY Catalina and PBM
Mariner patrol bombers and the later Coronado, and in single-engine planes such
as the Seagull scout, SBD Dauntless divebomber and TBM Avenger torpedo plane.
      President Bush, as a young pilot, may very well have operated the CRV-
23254 Control Box for a certain ARB and spun its tuning crank, as he flew the
fateful mission in his TBM on September 2nd, 1944, from the small carrier San
Jacinto.  Over the Japanese island of Chichi Jima in the Bonin Archipelago,
enemy flack stuck the plane and soon it and its three-man crew were plunging  
towards the East Philippine Sea.  When the American submarine Finback surfaced
some time later, Lieutenant George H. Bush was found to be the sole survivor. 
Somewheres, at the mile-deep bottom of the Bonin Trench, a certain ARB receiver
loyally waits, perhaps now bringing in deep-six DX for the many residents of
Davy Jones' Locker.


	           ARB, ATB MANUALS and INSTRUCTION BOOKS 

PB-14852    ARB Receiver Instructions (TO 08-5Q-3)			2-1942
PB-14913    ATB Transmitter (TO 08-5Q-51)				 1942
PB-23030    ARB Receiver Instructions					6-1943

NAVAER  08-5Q-3	    ARB Receiver, 195-9100 KC				c 1943
NAVAER  08-5Q-51    ATB Transmitter, 3.2-9 MC				c 1943