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These pagers were available in the former POCSAG net by Deutsche Telekom AG and later by e*message. The HF part of the receiver is identical to Skypers. The modification for 439.9875 MHz is thus the same. The shortcome is that the display is much smaller and there is no built-in function for setting time and date autmatically. In addition the date only allows years up to (20)13 starting from (19)94 to be set. This has to be done by hand and is lost on longer absence of battery power.

Modification for UHF ham band use

The original design of the pager is designed for usage on 466.075MHz. Same as for Skypers these can be modified for working in UHF ham band range and the German central frequency 439.9875MHz. Basic modification is to exchange the crystal of the Lo and removing the front end filter. It may be required to add two extra capacitors to make the LO work (not needed in my case however). After modification the pager has to be re-aligned with a signal generator.

Removing the frontend filter

Like the modification for the Skyper pagers it is necessary to remove the SAW filter which is desgined for 460MHz range. On this PCB you have to take care about the adjacent SMD parts at the outer pins of the SAW. Remove solder with a pump or solder wick on the in- and output. The middle two pins are GND and should be heatede at once to remove the filter afterwards.

 Removed SAW filter

When the filter is removed put in a little piece of silver wire to reconnect in- and output. A good source is the shortened ands of the crystal which is also exchanged. Of course this is just an easy hack and obviously reduces sensitivity. When re-adding the piece of wire be sure that it is not shortened to GND. It is recommended to add some heat shring tube to isolate.

 Reconnected in- and output of removed SAW filter

primodescription.1550752588.txt.gz · Zuletzt geändert: 2019/02/21 13:36 von df2et