I am trying to work out the arrangement of the cables linking the commander’s microphone and earphones to the radio in the US Army’s M4 Sherman.
Paul
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I guess you’ll find everything you need here (including complete TMs with drawings)
https://radionerds.com/index.php/Sherman_schematics
H.P.
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Pictures of the items are here
https://www.theshermantank.com/sherman/the-m4-sherman-tanks-radio-setup/
And the intercom boxes can be seen in some of the photos here at the various crew stations
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To try and break this down in simpler terms:
The Sherman radio assembly was mounted on a sturdy tray in the back of the turret bustle. This tray provided a physical mount to clamp to and was prewired with both built-in modular power connections as well modular out-put connections for both intercom as well as radio.
Standard radio arrangements for Sherman, Stuart, M-20 & M-8.
The first section is the transmitter with its push button selector for various channels, this unit also provides an internal intercom for the tank crew. The second section is a receiver. In the top photo the third section is another receiver so the commander may monitor more than one frequency channel if required. In the bottom photo the third section is a parts storage box.
Coming from behind this large radio tray assembly would be five heavy black shielded wires, each leading to a Como box located conveniently next to each personnel station in the tank.
Como Box
As an example a como box such as this would be located to the commander’s right, mounted to the inside turret wall slightly forward of the commander’s hatch, and another further down and forward for the gunner.
You can see an example of the heavy communication cable at the top of this photo. These cables are attached to the inside turret wall with small lap clips as you can see in the photo. The two 1/4’ phone jacks seen below the como box connect to the commander’s microphone and the other to his headset. This arrangement is the same for all five operators in the tank.
- Since the turret rotates, communication cables for the driver and co-driver do not go directly to these stations but must first go through the electrical slip-ring in the bottom center floor of the turret basket. (All electrical connections to the turret must go through this rotating slip-ring.)
- The switch on the combo box is an intercom/radio select switch. Under normal circumstances ONLY the Commander’s como box would ever be set to radio. I believe the two knobs are volume and squelch but my memory fails me on those items.
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FYI; interestingly there is a lot of chrome on ALL these radios. HONEST!
Here are my best modeling attempts to reproduce this arrangement seen here on an M-20, an M-4 Sherman and a Firefly. (The effort is rather wasted on the Firefly - Of course the Firefly would most likely have a British, not US radio!)
M-20 Sherman Sherman Firefly
p.s. FYI - I have actually assisted in installing/rewiring como and radios - as a two man team - on two Shermans and two Stuarts, back in the day at the Patton Museum, Ft. Knox.
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Note that your average M4 tank has the SCR-508 Radio Set installed in it. There were other radio configurations, though.
TM 1102704 Installation of Radio and Interphone Equipment in Medium Tank M4 Series
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