All homebrewers have tremendous egos, and I'm no exception. But, if you've got half a brain and N6QW points out a potential problem with your design, you damn well better listen!
Pete mentioned that he'd had problems with key clicks in one of his rigs where he keyed the final amp stage as I was doing, and suggested that I might be better off keying the driver stage. I hadn't noticed any clicks while testing, but I figured I'd better give it a close look. When I did, I still didn't hear "clicks", but the keyed waveform was definitely not optimally shaped. I was also having problems with my "Discreet Transistor Keyer", which wasn't at all happy trying to source an amp of current.
So, I followed Pete's suggestion and modified one of the prototypes by adding a PNP on the supply-side of the driver transformer's primary and played around with some RC values (using stray parts floating around on the bench) and came up with a combination that works fairly well. The revised schematic is shown below:
I think I mentioned this in an earlier blog entry, but you'll notice that I'm kind of anal about version controlling everything.
I don't do that for show - I do it because I've got a crappy memory and it helps me keep track of things. It's a discipline that my friend and Engineer Extraordinaire Bill Smith (normal person: no call letters) drilled into me, and I freely to admit that it's saved me a hell of a lot of time that would have been otherwise spent chasing my tail.
So, my advice for anyone pursuing the experimental method of anything is: Keep lots of notes, rev everything and maintain a history log.
73 de Steve N8NM
Pete mentioned that he'd had problems with key clicks in one of his rigs where he keyed the final amp stage as I was doing, and suggested that I might be better off keying the driver stage. I hadn't noticed any clicks while testing, but I figured I'd better give it a close look. When I did, I still didn't hear "clicks", but the keyed waveform was definitely not optimally shaped. I was also having problems with my "Discreet Transistor Keyer", which wasn't at all happy trying to source an amp of current.
So, I followed Pete's suggestion and modified one of the prototypes by adding a PNP on the supply-side of the driver transformer's primary and played around with some RC values (using stray parts floating around on the bench) and came up with a combination that works fairly well. The revised schematic is shown below:
I think I mentioned this in an earlier blog entry, but you'll notice that I'm kind of anal about version controlling everything.
I don't do that for show - I do it because I've got a crappy memory and it helps me keep track of things. It's a discipline that my friend and Engineer Extraordinaire Bill Smith (normal person: no call letters) drilled into me, and I freely to admit that it's saved me a hell of a lot of time that would have been otherwise spent chasing my tail.
So, my advice for anyone pursuing the experimental method of anything is: Keep lots of notes, rev everything and maintain a history log.
73 de Steve N8NM
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