My 2nd Homebrew Digital Interface

Well, not satisfied having to unplug the radio microphone and to plug in the digital interface plug every time I need to do digital mode communications, I decided to upgrade the design of my digital interface.

I was given a number of scrapped Siemens Gigaset phones with charger bases by a member of our radio club. I stripped a number of these units and found them interesting in respect of there design. Even though they appeared to be different on the outside, the motherboards were similar on the inside. 

Most electronic components are "surface mounted devices : SMDs" and I had fun trying / practicing to remove items and re-soldering them back. Then checking to see if the unit still worked. I my attempt to address the difficulties, I visited a local supplier of soldering re-work stations and was shocked to hear their prices. Finally bought some more solder wick and tried out some other ideas obtained from a Google translated Japanese website.  

Well a very surprising and successful outcome with some practice. I managed to remove SMD LED's, oscillator crystals, resistors, voltage regulators, a number of transistors, tantalum capacitors, diodes and quite interesting "zero Ohm resistors" !!!. Guess I will use these components sometime in the future. Even found an electronic catalogue via Google providing the equivalent technical specs.

Another interesting bit of detail was some of the integrated semiconductor components in these Gigaset units were labelled with unique "Siemens" code numbers for which there was no technical datasheet yet a number of Russian websites had these items "for sale".

The new interface was built and finally fitted into one of the Gigaset housings after I managed to work out how to open it. The tricks were all found using Google search. 

A few mods to positions of components and the task now completed.


The completed unit

The inside electronics showing the audio transformer, optocoupler, 5V voltage regulator,
relay for switching microphone / audio, relay for PTT indicator LED

Rear of unit showing RS232 PC connection, external power connection.

I am now going to build a second unit.

Unit was tested on SSB and using JT65. The switching unit "works for me".