If he is stuck on 136.550, it looks like he is using a Ropex Tx.
I have now modified two of them, that is installed a new crystal, which does
involve some major surgery. In addition, if one wants to be exactly on a
particular frequency (as we have to be with our FCC license: 136.750 +/- 7 Hz),
then some small adjustable capacitor must be inserted in series.
I would be glad to supply detailed instructions on the process to anyone
contemplating the re-crystallization (?) of a Ropex.
73
Andre' N4ICK
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'Geri' Kinzel, DK8KW wrote:

[...] I had exchanged some packet radio messages with Reiner, DL3FDO near
Frankfurt. Most of you will know his strong signal keepinng calling cq on
136.550 kHz.