A while go, I posted a link to AA5CK's website and his use of the iduino as a QRSS keyer. He used a little oscillator/buffer from Nightfire Engineering along with a home brew, single transistor amplifier.
So, I ordered two. And built one. At $7, who could resist?
It works, but it obviously isn't very pure. I'll get some a snaphot of the oscilloscope output sometime, but it is obviously flat on the bottom of the cycle, with a rather sharp and triangle peak. The tone sounds very
harsh in a receiver. It very obviously needs some kind of output filter. It does appear to be very close on frequency, maybe only 5 hertz low. The peak-to-peak voltage swing into a 50 ohm load was very nearly 2 volts, meaning that the output power is somewhere around 14mw with the 9 volt battery I was using as a supply.
Overall, my "ugly construction" 40m oscillator with buffer that I cribbed from EMRFD seems much cleaner. I suspect that in part this is because the vakits.com oscillator doesn't have a tuned buffer amplifier, but that's just my intuition.
I'd like to boost the output power to around 100mw (or maybe even a bit more) (perhaps with a class C amp) and obviously add an output filter, and then get it on the air.