Hello Alex and Everyone:
You would'nt happen to have a schematic and maybe some photos of this type of
plate choke arrangement with the tank circutiry also?
I am in the process of building a 4-1000 amp and have not decided on GG or
tetrode/screen supply operation.
I have not settled on the oputput network yet either. I have a large roller
inductor and two vacuum variables for the ouput (tank) network and I am quite
aware of the plate choke issue. At least one person has reported using relay
switched plate chokes to make sure they can use their amps on all the bands.
I would be very interested in seeing various solutions especially involving a
single 4-1000 tube.
Thanks,
Alton> From: alexeban@gmail.com> To: gswynar@durham.net; amps@contesting.com>
Date: Thu, 5 Feb 2009 15:29:24 +0200> Subject: Re: [Amps] Plate Choke Values> >
Merry meet you all:> Based on the past experience we had when working on high
power transmitters> at Elisra :> The impedance of the choke should be about 5
to 10 times the design load> impedance of the stage:> That calls for about 15
kilo ohms for a typical 1kW amplifier> That would translate to about 1.3mH for
1.8MHz operation.> The main issue however is the propensity for parasitic
series resonances in> such large chokes: not only is it getting lower in
frequency as the choke> get higher in value, it also gets more difficult to
place it between> operating bands, that got quite crowded with the WARC bands
in. > Our solution in the end was to switch over to series feed: band switched>
coils , parallel tuning and link coupling for the output.> It's not so bad as
it sounds: once set up, they're set forever and quite> wide band. You might
need only one or two coils to cover 21 or even 18 MHz> to 30 MHz.> It seems
it's easier to design and build such a tank circuit than a really> foolproof
plate choke.> > Alex 4Z5KS> > -----Original Message-----> From:
amps-bounces@contesting.com [mailto:amps-bounces@contesting.com] On> Behalf Of
Eddy Swynar> Sent: Thursday, February 05, 2009 2:35 PM> To:
amps@contesting.com> Subject: [Amps] Plate Choke Values> > Good Morning All,> >
Am I missing something here...?> > Extensive research here into years & years
of ARRL HANDBOOKS, Bill Orr> HANDBOOKS, and the internet have shed precious
little light in the matter of> optimum / minimum values of inductance for plate
chokes in the B+ leads of> our tube-type linear amplifiers.> > > Have a
look-see yourself: in designs that feature amplifiers that only go as> low as
3.5-MHz, you'll see chokes that range in value anywhere & everywhere> from
200-uh, to 50-uh. On 160-meters, I've seen quoted values as high as> 1.0-mh.,
and others as low as 200-uh.> > Just what, exactly, is a "...minimum reactance"
for a choke, on a given> frequency band, to do its job effectively, anyway...?
> > I know confusion can creep in in the form of the self-destruction of these>
parts if the hapless home brewer happens upon a band where there's>
self-resonance in the choke...but that issue aside, is this all some matter> of
"...by gosh & by golly black magic", or are there very real minimum> standards
& parameters that we should adhere to...? And if so, where are> said standards
published...?> > I certainly can't find them via "...the usual" routes --- but
again, I must> be missing something here...> > ~73~ Eddy VE3CUI - VE3XZ>
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