Collins RT-712/ARC-105 Restoration
to Phoenix W7CPA Page
Watt PEP USB, LSB, AM
I believe the
ARC-105 system was deployed on the
EA-6B Prowler, F-4C, F-105, RF4C, F-101 Voodoo, and early F-111. The ARC-105 was also used on the Sikorsky H3
Helicopters, tail numbers 777, 711 and 801 (from a Navy
technician). The high altitude O-Ring seal would sure keep out any
corrosive ocean air, good idea.
is not much
information floating around the Internet. I have received some feedback
from Air Force personnel to confim a few of these. It is a pressurized
version of the famous Collins R-618T-2 that is operational up to 75,000
feet. I decided to give this model a go because I could count on no
internal corrosion from laying around in warehouses. The
system consisted of the RT-712, 2 mounting racks, 1 cockpit control
head, 1 antenna tuner controller and 1 antenna tuner. See the
brochure for the model numbers. Phil at Fair Radio was very helpful
getting this madness started.
Letter from Naval Avionics Technician.
RT-712 is very similar to the 618T-2 but no internal modules are plug
compatible. Fortunately this model can still use the passive cockpit
control head (rotary switches and pots). The ARC-119 looks similar, has
another frequency select digit, and requires digital
communication to the control head - not recommended for ham
pin Amphenol front panel connector is available at Newark and Mouser.
The rear connector is of the unobtanium flavor. I am going to try
Amphenol, gold plated individual pin sockets with shrink wrap and
labels. A first RFQ pass through all the surplus
aircraft parts suppliers has turned up a used MT-3094/ARC-105
aluminum mount for $4,400- no way! The high pressure cooling air
connectors will be simple to adapt PVC pipes.
Receiver-Transmitter USB, LSB, AM, 400 Watts PEP (High Altitude
RT-712 Rack Connections
(Elecrical and Air) for PA and PA Connector Side
RT-712 PA Access Lid,
4CX-250F Vents and Beautiful, Compact, Collins PA Inside View
RT-712 Cover Off - Nice
Modules with Many Test Points and Annotations
Cockpit Control Head
found this in Israel via eBay. It was used with the RT 618T-2 so there
differences I can live with. The correct control head did not have CW
and Data selection, had a Self Test push button and a panel light to
show RF output. I'll either drill some holes, ignore or just remote the
in the box where I'll mount the unit in. The ARC-105 control
had a test switch, CW/Data, select, RF/Test indicator, and
select lines for the coupler controller only. These are not (hopefully)
required for ham usage.
Collins 714E-3 Control
Head - Will Need Some Adaption Since not Exactly the ARC-105 Mode
Aviation Headset - OK, So
I'm Getting Carried Away!
is high quality, normally very expensive, military helicopter headset
made by the famous Dave Clark Company. I found a NOS unit for $50 -
Headset by Dave Clark with 6 Pin U-229 Connector and PTT Box
Heat Exchanger Blower
RT-712 cooling design does not lend itself to cheap hammie Rontron fan
placement. Cold air must be circulated through the heat exchanger as
designed. An internal blower in the sealed heat exchanger assembly
distributes cool air to all of the plug-in modules via the vertical 1"
thick channel that all modules plug into. I found a 400Hz blower from a
retired radar system. A heavy duty food storage box from Bed and
Breakfast (heavy duty lid not shown) did the trick nicely.
400Hz Blower Assembler
400 Hz 3 Phase, 10KW Power Supply
Collins brochure shows that 400Hz 3 Phase, 115VAC, 1.2KW is
This is not something that one buy can buy from Astron or HRO.
Aircraft equipment runs on 400Hz to reduce weight. I found a
beautiful NOS 10KW
part out of a miliary helicopter. I believe it was a ground maintance
capability without having to drag/drive out a power unit out to the
aircraft. It operates with 220VAC 60Hz, single or 3 phase input. It
originally cost DoD $50,000 so I had to have it. Its 10KW capability
gives me good headroom <grin>. I tested it and it is
Mind you, the
horrendous fan noise is something I need to fix if I plan to
operate in the same room or the same house!
left unit does power factor processing and generates 400 VDC. The unit
on the right is a sophisticated 3 phase inverter that makes 3 beautiful
115vac, 400Hz waveforms with 10KW of ju ju!
Pastore (email@example.com) is a good source for surplus
military power supplies. He has a few of these beauties left.
Power Supply - Front
Power Supply - Mounting
Unit Connectors and Damn Fans
Power Supply - Back
Power Supply - Beautiful,
Overkill Cables and Connectors