Dispatching (english)

How to build a Skype-Radio-Modem

How to build a Skype-Radio-Modem

To set up the "Long-Range-Dispatching" which was first used at americaN in 2007, we had to build a Skype-Radio-Modem.

We wanted to use Skype, which is a free internet telephone tool, for free long range communications.

And we wanted to use radios at the railroad model.

There was no connecting modem to buy worldwide. At least we did not find anyone, and the internet search showed no results.

Michael Prader designed and built the basic Module:


It has two channels, one for computer --> radio and the other for radio --> computer. Each channel is nothing more than a low-frequency telephone transformer and a 10k-potentiometer. Thus, radio and computer are separated galvanically and the signal levels can easily be adjusted. There is no need for control signals or similar, as the radio’s built-in voice activation (called “Vox”) is used. A 2k2 resistor must connect the radio microphone and ground lines in order to enable the Vox functionality.

At the beginning of a session, signal levels must be adjusted, as there are many factors involved (think of all the possibilities to change volume and gain levels on your computer), however this should take only some minutes.

This interface can be used to bridge two radio networks, or connect a radio network to a remote computer (with headset and microphone).

Oliver Hampel put this equipment into the "black box":


the finished set up: Skype-Radio-Modem in the middle.