Hi Tomm,
A powdered iron part will still need quite a few turns.
For instance: 70 turns on a T-200A-2 will provide 100uH. This should be a
rough equivalent to the commonly used value. Try it?
Check for resonances in an installation & then measure how warm it gets at
3.5 MHz -- The air core chokes only have wire losses down there. This approach
will also have some core loss.
73 & Good morning,
Marv WC6W
-- Tomm Aldridge <KD7QAE@ARRL.NET> wrote:
Marv,
Thanks for the references, I will read them. To be clear, I was not
proposing ferrite toroids but powdered iron toroids as they can support
DC due to their distributed gaps.
Tomm
wc6w@juno.com wrote:
>
>
>>-- Tomm Aldridge <KD7QAE@ARRL.NET> wrote:
>>Why are plate chokes seemingly black magic? Don't you just want a >good
>>decoupling of the PS from the Plate; i.e. lots of impedance from >DC to Light
>>and no resonances? How I get that should not be an issue >but all teh plate
>>chokes I see are long skinny and sometimes segmented >single layer solenoids
>>of questionable wire size. Why wouldn't a >really lossy powdered metal
>>toroid with a few fat turns on it work, >assuming the inductance was high
>>enough?
>>
>>KD7QAE
>
> amps@contesting.com
>
> Hi Todd,
> No magic involved.
>
> A compromise was reached long ago that most ham amplifiers have employed
> ever since. By allowing the plate choke to carry some reactive current at
> its lowest frequency of operation, the value may be reduced such that only a
> single series resonance occurs within the 3-30 MHz region, which may then be
> conveniently placed at a "safe" frequency.
>
> The long form factor provides the best L/C(stray) ratio.
>
> This topic is well covered in: "R.F. Chokes for High Power Parallel Feed",
> by Vernon Chambers, QST, May 1954, pp30-33.
>
> A toroid would not be the best choice for a ferrite loaded plate choke due
> to the large DC component which would tend to saturate a closed magnetic
> circuit.
>
> A reference on this approach is: "A Unique RF Plate Choke", by Bill Deane,
> 73, Sept. 1969 p. 147.
>
> 73 & Good afternoon,
> Marv WC6W
>
> ___________________________________________________________________
> Speed up your surfing with Juno SpeedBand.
> Now includes pop-up blocker!
> Only $14.95/month -visit http://www.juno.com/surf to sign up today!
>
> _______________________________________________
> 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
___________________________________________________________________
Speed up your surfing with Juno SpeedBand.
Now includes pop-up blocker!
Only $14.95/month -visit http://www.juno.com/surf to sign up today!
_______________________________________________
Amps mailing list
Amps@contesting.com
http://lists.contesting.com/mailman/listinfo/amps
|