[Fwd: LF: Narrow band modes - anyone?]

[Andre' Kesteloot]

Andy Talbot wrote:

> Further to my last message on narrowband data modes.
>
> An alternative to PSK31 is 'Coherent' (BPSK)  and is probably somewhat
> easier for most people to generate on LF - at least for those using direct
> carrier generation rather than a transceiver approach.
>
> A simple diode ring mixer in the PA drive  (or even a changeover relay on
> the feed to the antenna !) will do the trick on transmit.   For receive, a
> simple interface needs to be built.  A version based on my PIC DSP interface
> with a different sampling rate and crystal is simpler still.
>
>  At 1115z  1998/01/03  I'm currently transmitting SLOWCW with 10 second dot
> periods on 137.76 as requested by Marco.  Only have 20 Hz steps so can't
> manage 137.77.
>
> Andy  G4JNT / G8IMR