UPDATE Feb 26, 2009
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I've added a couple of additional features to the QRP WSPR transmitter.
1. Completed the switched attenuator so that I can send at 23 dBM, 17 dBm and 10 dBm under control of the PIC.
2. Added GPS support (see below)
I use the GPS to get time of day information and also an accurate 1 pulse per second clock. This is used to update the time of day and to calibrate the symbol clock for WSPR (generated from the internal soft clock generated from the 32.768 Khz (nominal) crystal.
Being paranoid, I also added a thermal fuse to my "oven" so that power to the heater is removed (permanently!!) if the temperature inside the enclosure gets to 72C.
I got the TX on the air just after sunset local time today so missed the bulk of the day's propagation - that said, my first spot was from WA2YUN!
Look forward to getting spots - especially at the lower power levels!
ORIGINAL STATUS
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With thanks to Gene W3PM and indirectly to Johan SM6LKM, I am now on the air with a homebrew WSPR transmitter running 0.5 watts (antenna = 160m inverted L with remote tuner) on 30m.