[MRCA] J22/ARC-5 throat mic push to talk switch question

Tue Oct 12 10:31:08 EDT 2021

There isn't an AN/ARC-5-specific "throttle control switch for the arc five".  The throttle switch is part of the aircraft and not part of a specific radio set.

Electrically, the throttle switch is a spring-held normally-open push-to-close single-pole switch that grounds the radio set's keying circuit just as the PTT switch does on an RS-38 or T-17.  ANY similar switch capable of interrupting 30 vdc at less than 2 amps will work.

FWIW I have never read any WWII USN or USMC pilot's reference to using a throat mic.  The USN did not issue such things.

The historically-accurate representation of a typical three-receiver two-transmitter AN/ARC-5 radio set in a late war carrier-based single-seat fighter such as an F6F-5 would be unusable for most ham activities.

The three receivers would be:
R-4A/ARR-2 VHF ZB homing
R-26 or R-27/ARC-5 HF locked-tuned
R-28/ARC-5 VHF four-channel
These are controlled by C-38/ARC-5 with VHF channel selection by C-30A/ARC-5.

The two transmitters would be:
T-19, T-20, T-21, or T-22/ARC-5 HF locked-tuned
T-23 or T-126/ARC-5 VHF four-channel
These are controlled by C-30A/ARC-5 in VOICE mode.

This maked a very compact and capable set that provides one HF channel and four VHF channels for VOICE communications plus a ZB-homing receiver with six pilot-selectable MF modulation channels.  (This is the AN/ARC-5 and AN/ARR-2 configuration that I have assembled.)

Several photos of F6F-5 cockpits that I've seen show the AN/ARC-5 VHF gear replaced by the ten-channel AN/ARC-1, but I suspect that was very late or even post-war.

Mike / KK5F

-----Original Message-----
From: MARK DORNEY 
Sent: Oct 10, 2021 11:42 AM
To: Michael Hanz 
Cc: Military Radio Collectors Association 
Subject: Re: [MRCA] J22/ARC-5 throat mic push to talk switch question

you’re not going to believe this. I found the throttle control switch for the arc five. It’s overseas. We’ll see how that works out. Otherwise I’m thinking it’s simply a simple push button switch. 
73
Mark D. 
WW2RDO
On Oct 10, 2021, at 8:26 AM, Michael Hanz  wrote:
Perhaps you meant this for KK5F?  I only offered a possible throttle switch nomenclature for consideration.  (We're both named Mike, so confusion is inevitable.) 

Though the Navy rejected them, there had been a long ongoing attempt at improving the throat (more precisely the larynx) mic by the Signal Corps, probably out of embarrassment of perpetuating the use of a product they pioneered in the 1930s.  The last of the series, the T-30-P, Q, R, S, U, and V, were pronounced in T.O. 16-1-29 (25 April 1945) as being "...the only throat microphones suitable for use in aircraft.  Their performance is far superior to that of earlier models."  The last sentence was probably a plaintive plea to crewmen who had suffered through the difficulties of the earlier throat mics and were leery of glowing assessments because they knew better from experience.   All this "improvement" came about as a result of Bell Laboratories having labored mightily to make them at least marginally acceptable, despite their documented scientific conclusion after exhaustive testing that a throat mic "...would probably have been a very effective instrument but for the fact that the speech signal available from the larynx is intrinsically unintelligible".  These last gasp models had elements on both sides of the neck to enhance whatever phase subtleties might be gleaned from the larynx, and finishing touches like gold plated brass cartridges to minimize corrosion.  Making a silk purse out a sow's ear was eventually a bridge too far, unfortunately.  There is more on pages 131-133 of https://aafradio.org/docs/NDRC_Division_17_excerpts.pdf .

I have no doubt there were examples of Navy fliers "borrowing" some of the T-30 throat mics...using an RS-38 was as much a diversion as using a T-17, and Navy aircraft didn't often need to operate at very high altitudes during the first half of the war, despite most of the combat aircraft having oxygen capabilities with the vastly superior (from an intelligibility standpoint) oxygen mask mic.

I much prefer the H-46A/UR that you are planning to use (https://aafradio.org/flightdeck/H-46.html ).  With the chamois ear cushions, it is probably the most comfortable headset I've ever had.

- Mike  KC4TOS

On 10/9/2021 11:08 PM, MARK DORNEY wrote:
There is more than a few interviews with Navy fighter pilots that mention their use of throat mics.  Maybe not official by the manual use - more than likely more of a use of what was available sort of thing. I actually plan to connect a NAF headset with boom mic to this set up.  
Mark D. 
WW2RDO

On Oct 9, 2021, at 7:21 AM, Michael Hanz  wrote:

The AN/ARC-5 HF manual mentions NAF 1124-17 as the throttle switch, but it is probably not the only one:

- Mike  KC4TOS

On 10/9/2021 2:29 AM, Mike Morrow wrote:
The throttle switch is part of the top of the handle on the aircraft throttle lever, on the port side of the cockpit.  It is part of the aircraft.  There is likely some sort of NAF number associated with the throttle switch, but no JAN nomenclature.  The 3-pin A.R.C. 9488 plug for the J-22/ARC-5 (or J-16) should have two wires as part of aircraft wiring going to the permanently-installed throttle switch.  I don't know if there is typically a connector between the throttle switch and its aircraft wiring.  The throttle switch and wiring are separate from the mask mic and wiring until they get to the J-22 or J-16.

I find NO references to USN use of any "throat mic", which is very different from the mask mic that's mentioned in AN/ARC-5 instruction books.

Mike / KK5F

-----Original Message-----
From: Captain D. 
Sent: Oct 8, 2021 11:08 PM
To: 
Subject: [MRCA] J22/ARC-5 throat mic push to talk switch question

There is a 3 lead male receptacle on the J-22/ARC-5 jack box, below the hard wired cord that plugs into the throat/mask microphone.  Wiring diagrams say that this receptacle connect to a throat microphone push to talk switch.  Does anybody know the nomenclature of the switch? 
Thanks

73
Mark D.
WW2RDO

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-- Michael Hanz - KC4TOS

-- Michael Hanz - KC4TOS