Does anyone know what the |Z| of a typical electrolytic string
looks like at 1.8 MHz. Ignoring the electrolytic's impedance, I get
about 0.4% attenuation for a 180uH plate choke and a single .01uF
bypass capacitor to ground at 1.8 MHz. This would amount to an RF
voltage on the order of a few tens of volts across the bypass C in a
typical amateur amplifier. Whether or not this impressed voltage is
capable of generating any significant heating in the electrolytics
would depend on their shunt impedance at 1.8 MHz.
Someone mentioned using a 1000pf cap for the anode bypass. This
seems like it might be a little on the low side (4% attenuation could
imply a hundred volts of RF across the power supply on 160 meters).
Mike, W4EF........................
----- Original Message -----
From: "measures" <2@vc.net>
To: "jeff millar" <jeff@wa1hco.mv.com>; "AMPS" <amps@contesting.com>
Sent: Sunday, October 15, 2000 7:52 PM
Subject: Re: [AMPS] a sticky issue.
>
> >
> >Someone is certainly confused here.
>
> Amen, Jeff.
>
> >The HF RF bypass cap will
> >reduce 1.8 MHz ripple on the electrolytics. The problem with
> >ripple currents in the electrolytics has to due with resistive heating,
> >The designer usually sizes the caps to meet a ripple current heating
> >specification and if that ripple increases due to plate voltage swing
> >leaking back through the plate choke, the PS filter caps will operate
> >at increased temperature and somewhat reduced life.
> >
> >jeff
> >
> >----- Original Message -----
> >From: "measures" <2@vc.net>
> >To: "AMPS" <amps@contesting.com>
> >Sent: Sunday, October 15, 2000 7:31 PM
> >Subject: Re: [AMPS] a sticky issue.
> >>
> >> >In my determination, the ripple in the supply at 1.8 MHz is about
> >> >1/2 of a percent when actual impedances are considered. Hardly
> >> >enough to worry about.
> >> >
> >> Adrift in a sea of misunderstanding. // RF voltage on electrolytic
> >> filter caps is the main concern.
> >>
> >> >What major performance changes do you expect to see, if the 1/2
> >> >percent ripple is reduced from .5% to say .08 %?
> >>
> >> The HV RF bypass cap Has Nothing to do with ripple, Tom.
> >>
> >> > Or is this a "feel
> >> >better mod"? (Nothing wrong with that, as long as it doesn't hurt
> >> >anything else)
> >> >
> >> .... clueless
> >>
> >> end
> >>
> >> - Rich..., 805.386.3734, www.vcnet.com/measures.
> >> end
> >>
> >>
> >> --
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> >>
> >
> >
> >--
> >FAQ on WWW: http://www.contesting.com/FAQ/amps
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> >
> >
>
>
> - Rich..., 805.386.3734, www.vcnet.com/measures.
> end
>
>
> --
> FAQ on WWW: http://www.contesting.com/FAQ/amps
> Submissions: amps@contesting.com
> Administrative requests: amps-REQUEST@contesting.com
> Problems: owner-amps@contesting.com
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