HOW TO CHANGE THE EPROM OF HSN2

AND EXAMPLE OF TMN1 TX PLL MODIFICATION

These modifications of ancient Mobira radios are meant for licensed radio amateur use.
In addition to this modification you also need the ham software forthe radio.
If you don't know where to find it, tough luck...

These modifications are given as an example of a modification.
Your rig may have different components, their tolerances may be somewhat different and so on.
Please do not blame me if this doesn't work in your radio.

HSN2 modification

There are two screws under the display cover

and one on the other side under a plastic cap

Open the handset carefully, take the microphone away from the upper part.

The speaker leads are soldered to the circuit board - and glued to the eprom

If your handset doesn't look like this after it has been opened, you've probably
broken it - or it is of different model...

Take the eprom away. Use proper tools and do not bend the circuit board,
remember there's an LCD on the other side...

Just another picture, you can attach the PTT button
to the white connector - just follow Juha's example.

TMN1 modification

TMN1's RX VCO modified to 23 cm the stub length is about 8 mm.
The capasitor connected to the stub is changed to 1 pF (later I found out that 1.5 pF gives more stable oscillation)

On the next three pictures you'll see what happened.
The oscilloscope is showing the Lock Detect signal (pin 7) from the MB87006.

After the modification there is a perfect PLL lock at 1.241000 GHz

And perfect lock at 1.299000 GHz

The lock range is about 1230-1315 MHz in the room temperature.