[Amps] Plate Choke Values

[Alton McConnell]

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 at gmail.com> To: gswynar at durham.net; amps at 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 at contesting.com [mailto:amps-bounces at contesting.com] On> Behalf Of Eddy Swynar> Sent: Thursday, February 05, 2009 2:35 PM> To: amps at 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> _______________________________________________> Amps mailing list> Amps at contesting.com> http://lists.contesting.com/mailman/listinfo/amps> No virus found in this incoming message.> Checked by AVG - www.avg.com > Version: 8.0.233 / Virus Database: 270.10.17/1933 - Release Date: 02/03/09> 17:48:00> > _______________________________________________> Amps mailing list> Amps at contesting.com> http://lists.contesting.com/mailman/listinfo/amps
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