LF: Re: WSPR

["James Moritz" <james.moritz@btopenworld.com>]

Dear Mal, LF Group,

The transmited WSPR signal has a bandwidth of about 6Hz.

SSB mode is used for transmission in order to translate the soundcard audio
to the appropriate RF frequency. But the signal bandwidth remains 6Hz

At the receiver, a 200Hz bandwidth is extracted from the receive audio by
the DSP routines in the PC. This allows the transceiver to switch from TX to
RX without changing modes.  (In my case, I have configured the rig to use
the 250Hz CW filter as the "narrow SSB" filter, so the RX bandwidth is only
250Hz anyway).

This 200Hz of bandwidth is then sub-divided into numerous narrow 6Hz
sub-channels, that can be simultaneously processed to receive lots of WSPR
beacons operating simultaneously on slightly offset frequencies within the
overall 200Hz range. That's the beauty of DSP.

Overall, this means one transceiver can alternately transmit a WSPR beacon
signal and then receive many different WSPR signals within a 200Hz range,
during different 2 minute time slots.

Cheers, Jim Moritz
73 de M0BMU