Mobile Phone Conversion

Several fellow hams in the Asker and Bærum district have converted Mobira (Nokia) MD50 or MD59 Talkman NMT-450 phones from 1985-1988 to the 70 cm band. LA7TM, Nicolai, has played a central role in the conversion, based on the work of Finnish hams who pioneered the conversion and made their experiences and their software available. We then made some changes to the software. These changes are now included in the official Finnish version.

Push to Talk (PTT) button.

Mobile phones do not have a PTT button, and there is no clear candidate for this button on this phone. The Finnish software had the MPTT and the SPTT options, but in many people's opinion, the M requires too much pressure, and the S on the top of the handset is too far away from a natural position of the hand. Some years ago, LA7TM patched the binary code (ver 1.4) to make # the PTT. Then the * has the function of the original # (enter frequencies, memories etc), and the M on the side enables transmission with a 1750 Hz tone (S for the CU53 handset as there are no right-hand side buttons). The software therefore has a new option, HASHPTT, in addition to the original MPTT and SPTT.

Norwegian key-pad.

The Norwegian telephone key-pads in the mid 80's were different from the international ones. At that time, the Norwegian PTT required all telephone key-pads to be equivalent to those of calculators in order to minimize confusion. Actually this was a very good idea, but it was abandoned a long time ago as it is very costly to have particular national requirements in the global market place. The MD59 and MD50 in Norway had calculator keypads:

 International   Norwegian 

  1 2 3             7 8 9 

  4 5 6             4 5 6

  7 8 9             1 2 3

  * 0 #              0 * #

The MD50/MD59 software now has the NORWAY option to select this keyboard.

Software for MD50/MD59

The software version on this web page is based on the same source as the OH5NXO/OH3NWQ software. Download our tested version of the MD5x software for Norwegian keyboard (also found on the OH3NWQ site).

Other information on modification:

• OH3NWQ Software documentation
• OH3TR Ham conversion web page

Hardware Repair

After several years of use my MD59 would not turn off when the on/off switch was engaged. After having spent quite some time searching for the fault, it turned out that the main power relay, RE1, would not toggle. It is located on the Processor module board and it is a bistable relay which requires a negative voltage to change to the off-position. This voltage is supplied by a tantalum capacitor, C2 (47 uF), which no longer could hold its charge. Just replacing C2 repaired this condition.