A.R.C. Type 12 VHF AM Aircraft System

UPDATED 3/28/2024 (Aircraft installations, nomenclature clarifications)

The A.R.C. Type 12 components and systems were developed and marketed in the post-war period largely for the growing civilian aviation industry. They were used mostly on private and some US military aircraft in the 1950’s and into the 1960’s. Their “GA” light aircraft market focus was reflected in their eventual purchase by Cessna in 1959 as a wholly owned subsidiary. Collins, Bendix and others had the “high end” (heavy!) market covered.

L-19 Bird Dog. Copyright © 1956-2020 Planes of Fame Air Museum. All rights reserved.

The genesis from the WWII ATA/ARA, AN/ARC-5 and SCR-274N HF “Command Sets” is obvious. Those sets were also designed (and many built by) by Aircraft Radio Corporation in Boonton NJ who then adapted their business by moving into the civilian market.

Aircraft Radio Corporation (A.R.C. in this context) produced the “Type 12” as a big collection of avionics equipment to include communications radios and radio navigation equipment. This series includes ground-air radio systems as well as its test and alignment equipment.

In US military service, lightweight A.R.C. Type 12 VHF equipment was primarily used in early helicopters such as the H-13 Sioux, H-23 Raven, CH-37 Mojave and the UH-1B/C Iroquois. It also flew aboard the L-19 Bird Dog (above), L-20A/U-6A Beaver, T-34A Mentor and probably others. It even flew in high altitude manned balloon launches (Projects Man High/Excelsior).  They were also installed in some models of the U-2 aircraft. (Reference 62).

The U-2 installation is interesting, probably selected as the aircraft was designed to be as light weight as possible. The A.R.C. Type 12 VHF set fit the bill and did the job as it also did in the high altitude manned balloon tests for the same reason.

The most complete manual for the entire A.R.C. Type 12 system is the joint service Handbook Maintenance Instructions Radio Set ARC Type 12:

USAF T.O. 12R2-4-1-2 / NAVY AN16-45-122 June 1956. (Reference 113)

The VHF set works great on 2 meters AM with 2 watts output in Ham radio service.  The very “high fidelity” Super Het receiver that is tunable from 118-148 mc includes of course the current aircraft freqs. Did some “Surplus Perversion Manual” include a Ham-mering to “convert” them to FM? Probably. Groan.

Nomenclature confusion factor:  Sorry to belabor this point but I get a lot of questions on this topic. To beat that Dead Horse:

The A.R.C. Type 12 VHF set is not an “ARC-60” or AN/ARC-60. That is a UHF set it is commonly conflated or confused with. Nor is it the AN/ARC-12 UHF (RT-58) set they are also often confused with. Similarly, the “ARC-60” is NOT an A.R.C. Type 12 VHF set either.

Although the UHF AN/ARC-60 set includes 3 main components from the A.R.C. Type-12 product line, the A.R.C. Type 12 VHF sets were never designated as an “ARC-60” or AN/ARC-60 or anything else by the US DOD other than “ARC Type 12”.

The DOD had all those other possible WWII/Post-War VHF systems covered with existing equipment. Those would include the SCR-522, ARC-3, ARC-4, ARC-5 VHF and related ground/shipboard systems of that era. However the DOD did procure some A.R.C. Type 12 equipment in the mid-1950-60’s as Commercial Off The Shelf (COTS) gear for limited applications as in the above lightweight aircraft. Post-war the DOD moved quickly to UHF.

The Aircraft Radio Corporation catalog (1955) and the US Army’s TM 11-525-10 ARC Type 12 Operating Instructions manual (March 1958) simply refers to the entire collection of equipment as the “ARC Type 12”. Some individual components were given Joint Army/Navy numerical designations and are listed as such in Table 1-1 in that 1958 Army manual.  (Reference 111).

However 6 years later in 1964 the US Department of Defense designated the UHF-only sub system as the AN/ARC-60 within the DOD Joint Army-Navy AN/*** nomenclature system to fill a particular need. “ARC” in this nomenclature system denoting Airborne Radio Communications, NOT A.R.C. corporation. Confused yet?

As listed in Table 1-1 of the Technical Manual, the military nomenclature selected by the US DOD for the T-13A transmitter in 14 VDC configuration is the T-363/ARC. The R-19 receiver in 14 VDC configuration is the R-507/ARC. 28 volt transmitters/receivers are T-364/ARC and R-508/ARC respectively. The TV-10 UHF transverter is designated CV-431/AR. These designations were made for military procurement and logistics tracking purposes for those particular items.

As procured for US military service those particular “Type 12” individual components should nominally have carried their Joint AN military model sub-number designation tag although there are exceptions as in my R-19 receiver below.  Those may have been procured “COTS” prior to 1958. The equipment itself appears to be otherwise identical.

My R-19 (labeled) receiver carries a green U.S. Navy acceptance stamp on the front panel. (However it is not labeled as an R-507/ARC). “Never say never”.

The AN/ARC-60: This UHF set also flew in H-13 and H-23 helicopters along with the VHF sets as noted above.

MIL-HDBK-161-A /TM 11-487-A-1 clearly DEFINES the AN/ARC-60 as only consisting of the CV-431/AR UHF transverter, R-508/ARC receiver, a C-52 UHF radio control head, A-16 UHF antenna, junction box and associated accessories.  There are no VHF communications or navigation systems or capabilities associated with the AN/ARC-60.

The CV-431/AR UHF transverter receiver section had no RF amplifier stage, it was simply a 1N82 crystal diode mixer driven by the antenna signal and the 110 mc local oscillator. The transverter converted the incoming UHF antenna signals on 228-258 mc down to 118-148 mc VHF for the receiver. The receiver then operates in this system as a tunable IF stage; it otherwise provides no VHF communications capability.

The transverter also included a 0.5 watt UHF transmitter using up to 8 crystal controlled channels for operation between 228 and 258 mc. TM11-5821-205-12 O/M manual applies.

As with the Type 12 VHF set the D-10A dynamotor powers the receiver and the UHF transverter. (Reference 110). There is also a 28 volt version called a D-10A(28V). A.R.C. also produced transistorized replacements, the DV-10A and DV-11A for 28 and 12 volt systems respectively.

Below: My Receiver is a model R-19 (on the right), the Transmitter is a T-13A. These are commonly known by Hams as “Type 12” sets. Note the tuning spline drive routing to make this setup work in close quarters. A 12V wire pair terminated by a “cigarette lighter” plug makes it happen while mobile.

Above: My A.R.C. Type 12 portable lashup utilizing the R-19 and T-13A VHF components installed on their shock mounts. I had installed a small speaker for operational displays as shown. Included are the RS-38 microphone plus optional ANB-H1 headset. Ready for operations in your L-19 Bird Dog.

Also see my Radio News News section for information on performance in the field on 2 meters.

ARC Type 12 VHF AM set mobile N6CC

Above: The A.R.C. Type 12 set sitting on the seat for some VHF mobile range tests from Mt Diablo. It was driving a 5/8 wave vertical whip on 144.450 Mc to two other stations running USMC MAW sets in a portable configuration. One in San Francisco, the other at the Suisun Mothball fleet across the river.

When the &#@*^# APRS repeaters were not transmitting, good comms over the 25 and 15 mile LOS paths. APRS digital signals completely obliterated the receivers when they came on 144.390 Mc. (All VHF signals are strong up here – the dashboard altimeter indicates my elevation here was 2760 feet AMSL.) Too bad, otherwise a very viable radio network. And they sound great as well! As expected, the receivers slope-detect FM signals quite well too.

I am using a receiver control panel from an aircraft that provides the tuning dial and “sensitivity” control.  (There are at least 28 different system control panels available for this versatile, modular set.) I don’t have a transmitter or combined transmitter-receiver panel so I built a temporary, functional replacement shown here.

I had since added the second toggle switch so I can turn off the transmitter filaments when just receiving – to save battery power when necessary.  This panel includes a switch to select any of 6 installed transmit crystals although I currently have only one – 144.450 MC.

That 20 Amp fuse may sound excessive for a 12 VDC system – it is, but is needed to handle the startup surge of the dyno.  It is the correct rating for an aircraft-installed 12 volt system.

The crystal controlled transmitter used unique crystals (A.R.C. Part Number 14958). The crystals can be at either 1/12 or 1/18 the operating frequency; the multiplier stage tuning can accommodate either multiplier as necessary.

The A.R.C. crystals have the same 1/2″ pin spacing as the FT-243’s but their pins are slightly bigger in diameter than FT-243’s. FT-243 crystals will work in the transmitter but require small shims in the crystal sockets to accommodate the smaller pins.

I used an FT-243 crystal on 8025 kc to try to put it on 144.450 mc. (18X) This FT-243 required DIY pin adapter shims. In the stock circuit, it transmitted at 144.437 mc. So I brought the otherwise grounded pin of the crystal to chassis ground via a parallel combination of a 20 pf silver mica and a 2.5-23 pf ceramic variable cap. I can tweak it right to 144.450 MC at the antenna and it has been working fine.

The receiver is very sensitive and the transmitter sounds great with the issued RS-38 Mic (a T-17 works well also). The later production receivers included an effective front-panel squelch control, mine lacks it.

I am probably going to install this set in the Bronco using the remote control panels and the spline shaft for receiver tuning. Just need to find a place for it although it is kind of handy to use as a portable as well. Fun radio, sounds great.

Before I obtained the D-10A dynamotor I had designed and built a solid state dynamotor replacement that plugs into the rear of the receiver.  See below. It powers the TX and RX as the original dyno did with +250 VDC.  Works great….Much easier on the ‘ol battery during extended Ops….

Here’s the schematic “as built”.  Lab notebook page – please excuse the informality.  Probably not nearly enough windings to saturate the core but I had to work with the space available on the pot core bobbin.

A.R.C. Type 12 Solid State DIY Dynamotor
ARC Type 12 Solid State Dynamotor

I have a few local buddies in the San Francisco bay area that operate 2 meter AM gear, including the USMC MAW transceivers. Those are a late- WW2 design and they work pretty well once you get them tuned up. Get your buddies on 2 meters AM in your area – it’s lots of fun Off The Beaten Path.

ARC-Type 12 in the Field
ARC-Type 12 in the Field

Above: Powered by a 12 Volt garden tractor battery (and hence the solid-state dyno) on a recent field op up on the mountain. Note the additional transmitter filament switch on the TX control panel. Good AM comms with a buddy down in the valley. That J-45 CW key was connected to the adjacent TRC-77 HF-CW set also along for this Op.

If your buddies don’t show up on frequency with their AM sets, try listening to the VHF aircraft frequencies from 118 – 136 Mc. Lots of activity and you can get a good “receiver check” that way.

Another interesting trick is to listen to commercial A/C talking with Air Traffic Control; “United Airlines Flight XYZ climbing to Flight Level 36″….. Then look up United Airlines Flight XYZ on flightaware.com for a tracking map with their actual locations plotted. You can get an instant “range check” on your system by seeing how far away they are at the time.

For further details on the A.R.C. Type 12 equipment, see Mike Tauson’s (K3MXO SK) excellent summary pdf writeup on the Web, Reference 56.

Update:  I have received several requests for a “systems interconnect” diagram.  This is what I did, based largely on Mike Tauson’s article.  Apologies for the poor notebook photo.

N6CC A.R.C. Type 12 System Interconnects

Do a Search for: A Users Guide to Aircraft Radio Corporation Receivers. Thanks Mike, your work carries on.

Update:  Although the US DOD would disagree with Ray’s labeling that the “ARC-60” and the A.R.C. Type 12 VHF set is the same thing, it doesn’t matter. Ray has the GO-TO site for all things Type 12. Check it out. It includes detailed component and interconnect schematics.  Take a look: https://www.tuberadio.com/robinson/museum/ARC-60/