[Amps] 500 uh plate choke

Carl km1h at jeremy.mv.com
Tue Jan 22 15:59:13 EST 2013

Pi stands for pie Rob, resembles a pie plate.

In the "old days" the RF tanks were series fed so there was no concern about 
resonances and a lot of inductance was used.


----- Original Message ----- 
From: "Rob Atkinson" <ranchorobbo at gmail.com>
To: <k2vco.vic at gmail.com>
Cc: "Amps reflector" <amps at contesting.com>
Sent: Monday, January 21, 2013 7:46 AM
Subject: Re: [Amps] 500 uh plate choke

> That's a pi wound choke (I'd like to know why it is called that).  I
> usually see them in older ham AM rigs where the B+ is 1.5 KV or less
> and the Ip is no more than a few hundred ma.
> I am not saying it won't work in a modern RF power amp but all of the
> ones on the market today seem to use some sort of solenoidal wound
> choke.  Maybe that design is no longer manufactured in quantity?   I
> think they can't handle much more than 200 or 300 ma.
> I'd count the number of pi sections and look for a similar one at
> hamfests.  If you want something like 800 ma Ip and 3 KV Ep you are
> probably going to have to go with a solenoidal choke but I think you
> can achieve 500 uH with one.  Actually that RFC-4L choke is lower than
> I'd expect.  Most pi wound chokes I've seen are up over 1 mH, maybe
> even 2 1/2 mH.
> Rob
> K5UJ
> On Sat, Jan 19, 2013 at 1:44 PM, Vic, K2VCO <k2vco.vic at gmail.com> wrote:
>> This site
>> http://www.granta.g4axx.com/Linear_design_notes.php3
>> mentions a 500 uh plate choke specified as RF Parts no. RFC-4L. They 
>> tested
>> it and report that it has no series resonances between 1 and 100 mHz! RF
>> parts doesn't list this choke anymore. I would like to obtain such a 
>> choke
>> -- does anyone know if it is manufactured and if so who sells it?
>> Yes, it sounds too good to be true, but the site is very authoritative. 
>> They
>> mounted the choke in a box and used a vna to check it.
>> --
>> Vic, K2VCO
>> Fresno CA
>> http://www.qsl.net/k2vco/
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