ORIGINAL MESSAGE:
On Fri, 13 Aug 2010 12:33:12 -0500, "Roy" <royanjoy@ncn.net> wrote:
>
>"6A10s are a good choice, but for a high bias tube like a GS-35b you
>need a lot of them - about 40. (24 VDC x .6 V per diode)."
>
>
>CW key up / key down regulation is not good with a string of diodes. With
>a
>dozen I measured a droop of 1-volt. With a 50 w zener it was nil.
REPLY:
That's interesting, but I wonder how critical it is. With a fixed,
hard-regulated bias point, changing it a volt or so would have little
effect on the signal, so I'd think having it change with applied
signal shouldn't make much difference either. The efficiency would
shift around a little but I doubt you'd notice.
Since the bias would increase with applied signal, you'd want to have
enough headroom in the ZSAC to allow for that. IOW, son't bias it too
close to cutoff with no signal.
Roy, have you seen an actual degradation of the signal or other
problems?
73, Bill W6WRT
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TNX Bill,
I had 10k uF across the string then, running CW only, with 20 mA idling
current. So that was my concern too, that without the cap, the
close-to-class-B bias would transition "instantly" toward class C, resulting
in a hardened leading edge on CW elements. No one could seem to tell the
difference over the air though. My post was FYI...
73, Roy K6XK
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