[Lowfer] Re: BPSK31 (John Andrews)

[Clint Turner]

Ed Phillips asks:
>Question:  How is TAG generating the BPSK31 signal?  Some of out here
>on the west coast want to try both BPSK31 and PSKAM10 on VLF but don't
>want to go to the trouble of building an SSB transmitter.  

Years ago, I tackled a similar problem:  One of many solutions is described here:

http://www.ussc.com/~turner/psk_medfer.html

The modifications to make this a Class-E LowFER BPSK transmitter are rather trivial and have been covered.

It should be pointed out that if one doesn't bother doing envelope amplitude modulation, the penalty on receive is negligible.  The "clicks" on transmit due to the abrupt phase shift will also be contained by virtue of the high Q of any reasonable matching network used on a LowFER system - unless, perhaps, one is abutted against a band edge.

To make this work on PSK10, the varicode table would need to be modified - as would some timing in the software.  I would have done this already, but it wasn't particularly high on the priority list.

Clint