[AMPS] Series C at tube, Sorry, for C read L

[i4jmy@iol.it]

> >Sorry, brain slipped out of gear. Meant Series L.
> >cheers
> 
> //    More tubes in parallel proportionately lowers RL

Not necessarily it lowers because RL isn't inherently changed by tubes 
in parallel. To the limit, overall RL can increase if supply voltage is 
increased and current stay the same or even decreases.

> proportionately increases the amount of C-Tune

Again this is true if RL effectively decreases but in the other cases 
only the output tubes capacitance is what adds.
This capacitance increase without a compensating RL decrease can 
sometimes be a problem on high bands where a large residual capacitance 
(tubes + plateC + stray) can force to abnormally high loaded Q PI 
design.

73,
Mauri I4JMY


> needed to achieve the 
> desired Q of 10 to 15.  Thus, using 1, 813 or 6, 813s is essentially 
the 
> same game.  More tubes simply means Lower RL, More C-tune/C-load, 
Less 
> tank L, and More RF circulating current (approx. = Q x I-anode.).  
This 
> matter is yet another one of amateur-radio's, brain slipped out of 
gear, 
> tired old wives' tales.  
> 
> cheerio, Barry.
> --------------------
> 
> 
> > >----- Original Message -----
> >From: Tom Rauch <w8ji@akorn.net>
> >To: Randall DuCharme <kd5izi_tech@yahoo.com>; <amps@contesting.com>; 
Barry
> >Kirkwood <bjk@ihug.co.nz>
> >Sent: Thursday, 20 September, 2001 8:29 PM
> >Subject: [AMPS] Series C at tube
> >
> >
> >>
> >> > knowledge of use of more than a pair of them. They have rather 
high
> >> > output capacitance, therefore a tad of series C from plates to 
the
> >> > tuning cap is a good idea.
> >>
> >> Why? It certainly does not lower system Q. As a matter of fact, it
> >> raises system Q.
> >>
> >> It is a popular misconception passed along among VHF operators
> >> that a small series C between the tube an tank lowers Q. It
> >> actually does the opposite.
> >> 73, Tom W8JI
> >> W8JI@contesting.com



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