National Radio started the 2 section trend in the 1963 NCL-2000 and Alpha
used it starting with the 8n series.
Its not easy to modify an existing cap for a much lower minimum C as the end
plates are still too close to the frame. There also has to be sufficient
clearance between the 2 sections.
The Alpha cap is 10-58pf and 16-210pf with 3000V spacing which was fine for
the pair of 3CX800A7's they used at 2200V.
In the mid 80's I designed and had built a dual section with 10-53pf and
23-180pf with 4500V spacing and sold quite a few thru Radiokit into the
90's.
Carl
KM1H
----- Original Message -----
From: "Ulf (SM0NOR)" <ulf@sm0nor.com>
To: <ken.d.brown@hawaiiantel.net>
Cc: <amps@contesting.com>
Sent: Sunday, December 12, 2010 3:41 AM
Subject: Re: [Amps] PI-L Thoughts!
> Ok. Thanks.
>
> I'm looking at my 25-300 C1 and I got the idea to "chop" it up in two
> sections. It looks like a fairly simple procedure. Question is if the
> smaller section will render in a value low enough? The procedure is non
> reverseable :)
>
> Sent from my iPad
>
> On 12 dec 2010, at 09:31, Ken Brown <ken.d.brown@hawaiiantel.net> wrote:
>
>>
>>> 1, add a smaller C1 to the existing and switch in/switch out
>>>
>> You probably do not need to switch in/out the smaller variable capacitor,
>> because it will be an insignificant amount of additional parallel
>> capacitance on the lower frequency bands. You only need to switch the
>> larger variable capacitor out on the higher frequency bands.
>>
>> Another way of putting it:
>>
>> C1A = small variable
>> C1B = large variable
>>
>> Band ....C1 total=
>> 160...C1A+C1B
>> 80...C1A+C1B
>> 40...C1A+C1B
>> 30...C1A+C1B
>> 20...C1A+C1B
>> 17...C1A+C1B
>> 15...uncertain, maybe just C1A
>> 12...C1A
>> 10...C1A
>>
>> No need to switch C1A out for any band.
>>
>> DE N6KB
>>
>>
>>
> _______________________________________________
> 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
|