AN/ARC-51BX ?

[aseanaero]

Does anyone know which aircraft use an AN/ARC-51BX UHF radio ?

[Woodsy Airfield]

Aseanaero - I used to keep track of what equipment goes to what aircraft. I don't have info on the -51BX, but the ARC-51 was used with A-4M & N, A-7D and UH-1. The ARC-51A was associated with A-7E and P-3A & B.......Hope this helps.

Leon

[aseanaero]

Thanks Woodsy,

I just dug this up also.

It's actually the RT part of the set so the complete description is RT-742C/ARC-51BX

http://members.home.nl/a.k.bouwknegt/index_bestanden/ARC51_UHF_Transceiver.htm

UHF transceiver widely used in the seventies eg. F104 Starfighter. This remote controlled, very compact set, operates with AM in the 225-400 MHz military communications band., and was made by Rockwell-Collins.

The unit is powered by 28Vdc, and with 20W RF output, the input can be up to 300W. A control panel is needed to set the frequency.

The unit contains 11 (planar) tubes of 6 different types and 71 transistors.



Types
The ARC-51X had 1750 channels with 100kHz spacing, soon followed by the ARC-51A, B,AX or BX , with 3500 channels at 50kHz spacing. The A stands for a telephone impedance of 150 ohm, B is 600 ohm.

The "X" indicates that both fans are powered from the internal dc/ac/dc inverter. There is one fan inside ( sounds like a jet engine), and another outside the pressurized unit. Without the “X”, an external 400Hz source is required for the fans. Inside the unit are straps to select : carbon or dynamic microphone, 150 or 600 ohm telephone, silence or tone during channel selection, and 4 or 6 kHz audio bandwidth.



Frequency control

Three rotary knobs on the remote control panel select the tens of MHz (18 positions), units MHz (10 positions) and kHz (20 positions, in 50kHz steps). Each rotary switch position is transferred by 5 or 6 contacts to the ARC51-BX.

The receiver is a triple superhet, the first knob controls the first local oscillator (LO) , etc.

There are 18 + 10 + 20 = 48 Xtals, selecting 18 x 10 x 20 = 3600 channels. The first 100 are below 225MHz and may not function well.

During transmit (key down), the oscillator frequencies are added backward from third to first LO using the same IF filters as in the receive mode. This requires a lot of relays.

The intermediate frequencies are 20-30MHz ( tuned), 2.9-3.9MHz (tuned) and 500kHz (fixed). More details can be found here



The control panel C-6287/ ARC-51 allows manual selection, or one of 20 preset channels. Each channel is programmed by 8 pegs out of 19 positions on a rotating drum. For details and circuit diagram look here



Guard receiver

There is a separate receiver on 243MHz inside the ARC51, operating in the T/R+G position of the mode switch. When the frequency mode switch is in “GD XMIT“, the unit not only receives on this guard frequency, but transmits as well.



Circuit diagrams

External wiring to control, headset and power

Internal wiring and power supply

UHF modules RF preamp, RF poweramp, spectrum generator

First IF amplifier ( and 2nd IF, and 2nd and 3d LO)

Third IF amplifier

Modulator and audio ampl

Guard receiver

Mechanical tuner

I purchased the remains of 3 Westland Wasp helicopters (ex Indonesian Navy prior to this used by the Royal Netherlands Navy) and I just found the ARC radios in the 2 or 3 tonnes of spares I'm sorting through , I'm curious as to what other aircraft used them

[eric_stevens]

That Radio is scary I used to work on them in the Navy about 10 years ago. they were on the C-2 greyhound, Mh-53 Sea stallion, and the CH-46, as well as the SH-3. That radio was a nightmare to workon with the inductnace wheels and the capacitance blades. Aligning one of those was a treat. You would get a few channels to have good power then a few in the middle that had no power. I remember one of the hardest thingfs was to actually get all the modules back in correctly. Would never want to work on one again, good luck

[RickH]

We replaced the ARC51 in the A-4 with an ARC186VHF. It's almost plug and play. We use the ARC 51 in the TA-4 and Huey as ballast !

[Taigh Ramey]

Back in College days at San Jose State they were cleaning out old gear and were throwing away a bunch of aircraft stuff. I pulled out a complete avionics suite for a QU-22 (drone version of the Beech A-36 Bonanza) out of the dumpster. I found every wiring harness, junction box and component including an ARC-51BX. I plugged it all in and powered it up and it worked. I even made radio check calls to Moffett Field tower using a call sign for a P3... I was about 15 miles away and they shot right back with "loud and clear". Cool radio.

I have seen the ARC-51BX used in many different military aircraft from the late 60's through the 80's. Nice set but mostly for collectors and restorers today.

Taigh

[planenutti]

The H-46 also used them, maybe even the H-53. From a maintainers point of view, they were nasty but they were old when I worked on them.

[aseanaero]

It's funny when buying parts packages , the 'diamonds' are gone in a few weeks and you get your investment plus profit back quickly , items like the ARC-51 I call 'river rocks' they look cool , really hard to sell from Indonesia and hard to throw out so you start accumulating them. I started this business 3 years ago and have a growing collection of river rocks , about 50 tonnes now and just moved from a 3,000sq ft warehouse to a 12,000sqft warehouse !

The fun part for me is doing the research , making a bit of money and dealing with the characters that play with warbirds or repair and supply defence equipment (I sell to a lot of AMOs and workshops in the USA). I've had ONE bad debt in 3 years (from the UK) so that says a lot for the integrity of people and many have become friends also. It's great to go overseas and meet people face to face and see their 'toy collections'.

A friend of mine in Switzerland who deals in a lot of military equipment (he even has an ex Italian Air Force F-104G Starfighter in the shed) threw out 40 LTN-92 INUs from the C-130 as he figured everything uses GPS now , when I said I would have paid him $3,000 each (wholesale) for them he wasn't happy.

I still haven't made enough to get my own warbird as each time we make a profit it gets reinvested but I'm hopeful later this year I'll have a nice aircraft to play with and use for getting around various airports and airbases to look at projects.

[aseanaero]

http://members.home.nl/a.k.bouwknegt/

There's some good how it works info on this site for the models listed.