Santa gave me a new WSPR transmitter for Christmas, the kit arrived from England well before christmas and was assembled in a few hours, since then it has been running on the bench, as I played with its many (9) different modes of operation.
Then came the task of putting it in a box and adding the finishing touches, and finally the big moment yesterday I connected it to the antenna.
What can you expect from two intergrated circuits, one a 74HC00 logic chip the other a small AT microcontroller with two 2N7000 MOSFETs as the PA, running from a 5 Volt supply pulling 110mA on transmit, the answer is 8.4volts P/P on 50 ohms, a quick calculation 175mW, increasing the PA volts (only) to 6 Volts produced the desired 9V P/P or 200mw RF output.
A quick touch up of the frequency to 10.140170MHz, selecting WSPR Mode and setting the realtime clock to UTC and into the antenna, a Vertical Moxon Rectangle (top at 30 ft reflector at 6ft) a real NVIS cloud warmer, SWR 1.2:1 and fingers crossed, where will my 200mW go.
Two and a half minutes later the answer a +10 s/n spot from VK4TMH 507km away a good start, as the afternoon progresses the reports get better VK5ZEA @ 1.817km, WA2YUN @ 5,409km, KL1X @ 11,169km, W5Olf @ 12,805, then just before bedtime several -28 s/n spots from OH8GKP @ 14,502km.(a total over 75 spots in 5 hours)
A quick final technical check, 200mW yes, the 2n7000's do run a little warm at that, but at 60 cents each that is not a worry, the realtime clock once set has kept time to better than a second (or my windows computer without help), the frequency has slowly drifted a few Hz with a 5 degree C change in ambient temperature.
(I am not at this stage using the external GPS time frequency input option provided in the software).
So we now have a viable battery powered, stand alone 200mW WSPR Beacon transmitter that works. (time to think about a small solar panel battery charger)