Stewart,

Wow! This sounds very interesting. My comments will be mostly from the U.S.
"Lowfer" perspective.

Receiving:

R1: Loran lines are very faint in the 160-190 kHz range, particularly in the
upper end where most U.S. activity occurs, so use of this option would be
restricted to receiving EU signals on 136. The intermittent presence of CFH
on 137.0 would make the SSB filter approach somewhat difficult for fellows
in the eastern U.S.and Canada.

R2. Again, the SSB filter would be a drawback. In the eastern U.S., QRM from
broadcast operations on 183 and 189 kHz is an issue. Anything which makes
that worse should be avoided.
R3. My vote goes here. My receiver derives all frequencies from a single
L.O. But probably due to integer math in the DDS, there is a 55 milliHertz
offset in the output audio. As long as the WOLF decoder can be set to accept
the offset signal, I would be OK.

Transmitting:

T1. That would be my preference. Be advised that we have experienced timing
problems with the "keyed tone" approach. The issues should be less with
rates of 1 b/s, however. Could you use the RTS pin on a serial port instead?

T2. This would be my second choice, and it does eliminate the timing issues
with keying. My guess is that the U.S. guys would prefer the T1 option,
though.

T3 and up. Since I have already voted for the use of a GPS receiver for
controlling the receiver L.O. and the decoder/encoder timing, these options
are of less interest. But I would defer to those with GPS setups that do not
have a disciplined oscillator.

John Andrews, W1TAG