These are run by solar panels that only transmit during the day. The capacitor just gives a half a minute or so in the event of brief cloud cover, panel not fa

These are run by solar panels that only transmit during the day. The capacitor just gives a half a minute or so in the event of brief cloud cover, panel not facing the sun at a good angle, etc. Not strictly necessary, but since a WSPR message takes almost two minutes to send, a good idea to not have it abort in the middle of the transmission due to lack of power for a couple of seconds.