13 December, 2013

Adding radio comms to a German Army field telephone

I was asked a while ago if I could make an old bakelite German Army field telephone work as a walkie-talkie.

Bundeswehr field telephone, circa 1970.

It would be used by a WW2 airsoft re-enactor to communicate with the rest of his team in a more authentic manner. Even though it is no where near as old as a WW2 original it certainly is a very close relative, as can be seen from this photograph.

Wehrmacht field telephone, 1941.
Image copyright: The Museum of Technology 

It's a close enough match that you would need to be close up and knowledgeable of German Army field telephones to know that it is not WW2 era. This is fine for an airsoft prop for a casual re-enactor.

Both of us would have reservations on 'hacking up' an original WW2 object simply for the purposes of an airsoft prop. The 1970's field telephone comes from less important period in history and there are many more of them around, so we felt that it was much less of a travesty.

The approach I took was to externalise the mike, speaker and push to talk switch via the headset socket, which can be seen in this next photograph. The grey circular thing is the mike from the field telephone and the little black speaker is from the radio.

Prototyping the electronics

I later successfully also used the speaker from the field telephone but it was quite large, and I thought the current from the radio would not be sufficient to drive it at acceptable volumes, and this is why I initially used the radio speaker. In the end, it worked perfectly. I also initially used the mike from the radio, but I cooked it during the de-solder process and it was absolutely ruined. With a lack of spare mikes to hand I was (luckily) forced to use the grey one. Note also that in the photo above the black vinyl cable is not very WW2 looking. I stripped out the wire cores from the braided black nylon cable and re-cored it by hand with modern cable, so its olde-worlde on the outside but modern on the inside. ;) I also buggered up my hands with friction burns in the process. It looks like I have been abseiling without gloves :(

The field telephone headset integrated with the radio

In the above photo you will notice a grey bar on the headset. I wired this into the system and it now functions as a push to talk button. The system can be fully used, as pictured in the photo above. The base of the field telephone actually has no function in the rewired system other than looking authentic.

The complete system
With all the components of the system together it is ready for use. Hopefully I can get a pic of it in use to post.

As always, thanks for reading! :D