[amsat-bb] Re: Landwehr 2m Preamp Help/Info & Manual Request

[Alan P. Biddle]

Doug,

Attached is a PDF of the Landwehr preamp "manual," though the BB copy will
strip that off.  As I mentioned, they do not give the component values,
which was very typical of European products of that period.  Landwehr is
still is business, though they are no longer selling ham gear, and they may
be able to provide some information.  http://www.le-tronic.com/

You mentioned that it was switching between RX and TX in receive mode.  TX
mode is almost identical to unpowered, but there is a way to tell the
difference.  Hook up a ma meter in the 12 V line.  In RX mode, it should
draw about 100 ma.  If it is in fact switching to TX mode, the draw should
be much less, probably around 5-10 ma, as the TR relay is de-energized, and
the preamp circuitry is (probably) unpowered.  Only the switching
electronics should be drawing.  If the draw is 0, then you have a loose
connection in the 12 volt line, most likely in the connector, which should
be easy to locate and repair.  

Hope this helps.

Alan
WA4SCA