In a series circuit, lower C, and larger L implies higher Q. The capacitors
in a T network are in series, and thus see a voltage drop that is equal to
something like Vin/Rin*Xcin = Vin * Xcin/Rin = Vin*Q. In a PI network,
the capacitors are shunt elements, and thus see a circulating current
Icir = Vin/Xc = Iin*Rin/Xc = Iin*Q. In this case, Q is inversely proportional
to Xc instead of proportional to Xc as with the series case.
73 de Mike, W4EF.....................................
----- Original Message -----
From: "2" <2@vc.net>
To: "Tom Rauch" <W8JI@contesting.com>; "Amps Reflector" <amps@contesting.com>;
"Jon Ogden" <na9d@speakeasy.net>
Sent: Wednesday, June 20, 2001 11:24 AM
Subject: Re: [AMPS] Review of Antenna Tuner from Dayton
>
> >
> >
> >> My first stop was to look at the Ameritron/MFJ/Vectronics units. After
> >> all, they are the most prolific tuners out there right now. Upon looking
> >> at all these units, I found that the plate spacing on their caps were no
> >> better than what my Heathkit had. Even their highest power units had caps
> >> with the same spacing. It is interesting to note that later I noticed
> >> that the Ameritron tuner rated for 1200 Watts has larger cap spacing than
> >> the ones that are more expensive and rated for higher power!
> >
> >Well Jon, it might be advisable to spend time looking at voltages in
> >T network tuners. If you run the numbers, you'll see the largest
> >problems causing arcing are excessive Q on the low bands.
> >Excessive Q is caused by not having enough capacitance.
> >
> /\ More C (and less L) usually means more circulating current - which in
> turn means higher Q.
>
> > ...
>
> cheers
>
> - R. L. Measures, 805.386.3734, www.vcnet.com/measures.
> end
>
>
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