Rik Strobbe wrote:
> if I got it right WSPR is a 4-FSK mode and does not require linear
> amplification.
Correct, and, according to Joe K1JT, a "FSK tone accuracy" of 0.1Hz or
so is enough to not compromise performance too much (FSK tone spacing is
~1.46Hz). The QRP minded can easily achieve this accuracy with a simple
VCXO which Peter DL6NL has shown with his PC-less WSPR beacon which has
been on the air 7*24h for half a year on 30 meters. He is using a PIC
microcontroller together with a QRPp TX of his own design. A simple PIC
based WSPR beacon controller for VCXO or AD9850 DDS can be found here:
http://web.telia.com/~u33233109/mept_jt/mjb002.zip
The current version transmits WSPR modulation only but the firmware can
easily be modified to insert traditional CW IDs at regular intervals to
enable reception at such remote places as a misspelled Scraborough.
73 Johan SM6LKM
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