Thanks for repeating what John posted yesterday.
BTW, I have read those GE Ham News articles from the originals in the
library here.
And as usual, John, K5PRO, has it correct.
Carl
KM1H
----- Original Message -----
From: "Gary Schafer" <garyschafer@comcast.net>
To: "'Carl'" <km1h@jeremy.mv.com>; <dezrat1242@yahoo.com>;
<amps@contesting.com>
Sent: Monday, February 22, 2010 1:03 PM
Subject: RE: [Amps] 120 Hz hum from Henry...
> Old news yes, but old dogs may want to learn from it. :>)
>
> Reading the voltage swing on the plate volt meter is not looking at
> dynamic
> regulation of the power supply. It is showing you the static regulation as
> the meter is too slow to follow.
>
> I highly recommend reading the articles from "GE ham news" that John K4PRO
> referenced on power supply dynamic regulation. It spells out exactly what
> is
> being talked about here.
>
> Note in the article that with a 20 henry fixed and a swinging choke that
> using a 45 microfarad capacitor still gave a dip in the high voltage. It
> took around 90 microfarad to eliminate it. And that was on a 250 ma
> supply!
>
> I have quoted Johns email here:
>
> "There is some information here from the old GE Ham News, on power supply
> dynamic regulation, on the AM Window:
>
> http://www.amwindow.org/tech/htm/tutor.htm
>
> Also a paper by Wallace Walhgren of the former Electro Engineering, now
> Stangenes Transformers, on transmitter performance without filter chokes."
>
> 73
> Gary K4FMX
>
>
>> -----Original Message-----
>> From: Carl [mailto:km1h@jeremy.mv.com]
>> Sent: Sunday, February 21, 2010 8:17 PM
>> To: garyschafer@comcast.net; dezrat1242@yahoo.com; amps@contesting.com
>> Subject: Re: [Amps] 120 Hz hum from Henry...
>>
>> Thats old news, a couple of caps takes care of that.
>>
>> Carl
>> KM1H
>>
>>
>> > The choke will improve the "static" regulation but will kill the
>> dynamic
>> > regulation.
>> > Hook a scope up to the HV and run some CW with your key. You will see
>> > negative spikes in the HV. Same on SSB.
>> >
>> > 73
>> > Gary K4FMX
>> >
>> >> -----Original Message-----
>> >> From: amps-bounces@contesting.com [mailto:amps-
>> bounces@contesting.com]
>> >> On Behalf Of Carl
>> >> Sent: Sunday, February 21, 2010 1:43 PM
>> >> To: dezrat1242@yahoo.com; amps@contesting.com
>> >> Subject: Re: [Amps] 120 Hz hum from Henry...
>> >>
>> >> A choke input filter with sufficient L or a swinging version will
>> >> improve
>> >> dynamic regulation over the typical commercial amps single C in any
>> >> class of
>> >> service. They were used for decades, and still are, in Class AB and B
>> >> modulators.
>> >>
>> >> My 1200W LK-500 SSB/CW amp with 26uF filter has a 400-450V swing on
>> the
>> >> meter. My PP 304TL modulator with an untuned 20H choke input and 24uF
>> of
>> >> C
>> >> has a 200V swing. The only purpose of choke tuning was to be able to
>> use
>> >> less inductance but there have always been reliability tradeoffs.
>> >> Sometimes
>> >> bigger is better.
>> >>
>> >> Carl
>> >> KM1H
>> >>
>> >>
>> >> ----- Original Message -----
>> >> From: "Bill, W6WRT" <dezrat1242@yahoo.com>
>> >> To: <amps@contesting.com>
>> >> Sent: Sunday, February 21, 2010 12:57 PM
>> >> Subject: Re: [Amps] 120 Hz hum from Henry...
>> >>
>> >>
>> >> > ORIGINAL MESSAGE:
>> >> >
>> >> > On Sat, 20 Feb 2010 11:29:34 -0600, "Roy" <royanjoy@ncn.net> wrote:
>> >> >
>> >> >> Read the article,
>> >> >>noting the careful tuning to exactly the 120 Hz resonant frequency:
>> >> >>http://www.qsl.net/i0jx/supply.html
>> >> >
>> >> > REPLY:
>> >> >
>> >> > In that article, the author states:
>> >> >
>> >> > "There are however other approaches offering better regulation
>> >> > performance (i.e. output voltage stability) at the expense of
>> higher
>> >> > complexity and cost; in particular the Input Choke Power Supply
>> >> > (ICPS), in which a choke (L) is inserted between the diodes bridge
>> and
>> >> > the capacitor, as shown in Fig. 2."
>> >> >
>> >> >
>> >> > That statement is true only in the case of a steady current draw
>> (AM,
>> >> > RTTY or FM). In the case of CW or SSB, a choke actually decreases
>> the
>> >> > dynamic regulation. A choke naturally opposes any change in DC
>> current
>> >> > flow through it and the result will be spikes in the voltage across
>> >> > it, which are in turn applied across the capacitor and thus the
>> >> > output. A large capacitor will absorb the spikes to some extent,
>> but
>> >> > can never eliminate them completely. A few minutes with a scope
>> will
>> >> > confirm this.
>> >> >
>> >> > When AM became obsolescent, so did the choke-input filter. For
>> today's
>> >> > amps a simple C-input is best.
>> >> >
>> >> > 73, Bill W6WRT
>> >> > _______________________________________________
>> >> > Amps mailing list
>> >> > Amps@contesting.com
>> >> > http://lists.contesting.com/mailman/listinfo/amps
>> >>
>> >> _______________________________________________
>> >> Amps mailing list
>> >> Amps@contesting.com
>> >> http://lists.contesting.com/mailman/listinfo/amps
>> >
>
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|