SEM 52-A Crystals
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Swapping crystals

The SEM 52-A has six channels, all crystal controlled, numbered A to F. The frequencies of these channels can be changed by swapping the channel modules - actually crystals mounted on very small boards - in the rotary channel selection switch, after opening up the radio.
The two highest channels, numbers E and F, are always on the same frequencies and have fixed channel modules. Channel module 5 is marked red and is on 47.800 MHz; channel module 6 is marked green and is on 55.500 MHz.

For channels 1 to 4 - A to D - there are a total of 24 exchangeable channel modules. However, these were not used freely. They were issued in six sets of four channels each, in channel module boxes. In total there could be six different channel plans in action at the same time, with only channels 5 and 6 overlapping between the six groups. Changing a SEM 52-A from one channel set to another is quite quickly done with the tools provided in the channel module boxes and would be done in the field.

Sometimes one can find the complete channel-sets in surplus, sometimes the individual channel modules. Both are rare up to now.

The channel modules are only distinguished by their position in the channel sets - they are stamped with a letter and a number. They are not marked with their frequencies. The Frequencies page gives the pertinent information. On the Channels page one can find the ordering of these frequencies in the original channel plan - i.e. the channel boxes.

I have some extra crystals available for swapping - and I am looking for a number of them as well. Check my Crystal Swap page and let me know if we could help each other.

The original channel modules are packed by the manufacturer, Standard Elektrik Lorentz, in foil packages measuring approximately 10 by 16 centimetres - the modules inside the envelopes are wrapped in bubble foil. Sometimes the package contains extra drying agent. The individual packages can also be found in heavy cardboard boxes of ten.

The individual original packages typically are labelled as follows:

-- 57400 42109
1          EA
B/IA8            DAT.: 08/91
Reissued crystals have been found packed either in sealed paper bags or small cardboard boxes, with either handwritten on it just the Versorgungsnummer or a printed label with sometimes only partial information. The best way to identify the package is either through the Versorgungsnummer if present, or by the letter-number stamp on the actual board.

Last updated: 12-11-2003 23:13 +0100
Copyright 2001, 2002, 2003, 2004, 2005 A.J.M.O. Witkop. All Rights Reserved.