Wolf,

you mentioned a cheap LPD solution, which, off course, would also be
necessary for any unattended use according to the German regulations.
Depending on the distance between the remote receiving site and your house
you might want to look into wireless microphones, that usually have a high
dynamic range and also allow unattended license-free use. For the legal use
you would only need the transmitter, the (normally more expensive) receiver
can be replaced by something homemade. There are wireless microphone
tranmitters available with a microphone connector to it (to which you can
connect your LF receiver) for example in the 800 MHz range, which should
allow quite a good range of several hundred meters (with 10 mW output),
provided you use a directional antenna at the receiving site. Another
possibility might be to look into a (license free) 2400 MHz Video link ...

Best 73

Geri, DK8KW (W1KW)

... still without LF antenna at the moment, but will be back on the air
hopefully during the next winter-LF-season ...