|[AMRadio] Step Start|
brett.gazdzinski at verizonbusiness.com
Tue Dec 12 19:22:20 EST 2006
Nice to talk with you today on 40 meters Don.
I build step start into everything, as I use
solid state rectifiers, and often go over
I am not sure if the mercury vapor things hold up
better or worse then the solid state stuff under short
I am not fond of MV, warm up time, filament transformers needed,
they take up lots of space, toxic waste, etc...
> > This is a choke input with two 4 mf in parallel across the
> output and
> > somewhere it seemed to imply that the step start was only
> needed for cap
> > input.
> > As far as I can get with the heavy math, it seems like the resistor
> > required would only be a few watts as it is only dealing
> with the 100k
> > bleeder as a load.
> I'm not sure how much plate voltage and current you plan to
> run from the
> power supply, but it has been my experience with loads on the
> order of
> 2000-2500 volts at 600-700 mills or so, you don't have to
> worry about the
> need for step-start with choke input filter using a swinging
> choke, until
> you go beyond 25 mfd of filter capacitance.
> My 8005 rig runs at 1300 volts on the plate, with total drain
> from final,
> modulator and audio driver plus bleeder resistor, somewhere
> in the vicinity
> of 700-800 mills. I use a 52 mfd filter with no step start without a
> problem. The filter choke in that rig is non-swinging, 10
> Henries @ 1 amp.
> The p-p 845 audio driver stage stays on all the time and
> pulls about 150
> mills, acting as extra bleeder, holding the voltage steady
> even for cw
> operation. Add the steady 320 ma drain from the final during
> AM operation,
> and the plate voltage is very stable during modulation, which
> keeps the
> class-B modulator stage happy.
> Don k4kyv
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