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Thank you for all the suggestions and exchanging of ideas of the different approaches. The reason for my question is explained in my original post. Maybe a little more detail; I have a very simple low-power 200mW RF transmitter beacon sending very slow Morse code known as QRSS as FSK (+/- 5 Hz and each dot element in this case is 3 seconds) on the 30 metre QRSS frequency of 10140 kHz into a resonant antenna. Circuit below. It is one of Hans Summers (G0UPL) early kits.
At the moment night-time propagation on 30m is poor to non-existent, so daylight-only operation is fine for the time being. I wish to operate the transmitter without a mains power supply while I am away for extended periods, hence the use of one SX305M 4-watt solar panel.
While away I was watching its trace on various international QRSS grabbers, but after a day or two my signal disappeared. Poor propagation maybe? Then I noticed what turned out to be my carrier without FSK and other days rapid, seemingly random FSK!
When I returned to have a closer look I thought the ATtiny13 had failed, but with a steady 5V supply it was fine. After a day or two I realised it was probably due to the very gradual DC voltage supply increase in the morning (well before the LM705 regulator reaches its stabilising voltage) which obviously confused the keyer chip, even once the sun is bright enough to provide 5V from the voltage regulator. Hence my request for something that only applied volts to the LM7805 when it reach about 7 or 8V.
It has since occurred to me that a 12V relay (maybe with some series silicon diodes to ensure it doesn't switch on at too low a voltage) might also work, but I don't have one, but I do have the components for the circuits presented above. As suggested, using the solar panel to charge a battery and keep the voltage stable 24/7 is of course another solution. Anyway, thank you all for your help.
At the moment night-time propagation on 30m is poor to non-existent, so daylight-only operation is fine for the time being. I wish to operate the transmitter without a mains power supply while I am away for extended periods, hence the use of one SX305M 4-watt solar panel.
While away I was watching its trace on various international QRSS grabbers, but after a day or two my signal disappeared. Poor propagation maybe? Then I noticed what turned out to be my carrier without FSK and other days rapid, seemingly random FSK!
When I returned to have a closer look I thought the ATtiny13 had failed, but with a steady 5V supply it was fine. After a day or two I realised it was probably due to the very gradual DC voltage supply increase in the morning (well before the LM705 regulator reaches its stabilising voltage) which obviously confused the keyer chip, even once the sun is bright enough to provide 5V from the voltage regulator. Hence my request for something that only applied volts to the LM7805 when it reach about 7 or 8V.
It has since occurred to me that a 12V relay (maybe with some series silicon diodes to ensure it doesn't switch on at too low a voltage) might also work, but I don't have one, but I do have the components for the circuits presented above. As suggested, using the solar panel to charge a battery and keep the voltage stable 24/7 is of course another solution. Anyway, thank you all for your help.
