[AMRadio] Step Start

Brett gazdzinski 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
50 UF.

I am not sure if the mercury vapor things hold up
better or worse then the solid state stuff under short 
term overloads.
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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