The results of modeling with a serial inductance from plate to PiNet
are in...sorta. I still couldn't find a combination that lowers the Q.
Here's a table of results. The following table is for a single 813 at
2250V and 145 ma, class AB, plate load of 10K. Cout for the tube
is 18 pf, L1 is the series L (uH), C1 is the PiNet tune cap (pf), L2
the pinet inductor (uH), and C2 the pinet load capacitor (pf).
In each case below, the network matched from 50 Ohms to 10K.
L1 C1 L2 C2
.7 18 .80 400
.4 16 .90 470
.1 15 .87 500
.3 30 .60 600
.2 30 .62 640
.4 30 .59 570
.3 10 .98 360
.4 10 .93 350
.5 10 .88 340
.6 10 .83 330
.7 10 .78 320
.8 10 .72 310
.9 10 .66 300
1.0 10 .59 290
1.1 10 .53 280
Without L1 and using Cout for C1, the values were
0 0 1.6 240
Q corresponds to the value of C2, lowest Q at lowest C2. From
the tables, the lowest Q occurs with a conventional PiNet with Q=35
(as I recall). All the series inductor cases tried raised Q and narrowed
the frequency range of match.
Conclusion: The series inductor doesn't help lower Q with any
combination tried. I tried to find an inductor value that canceled
the tube's reactance but it the L network doesn't appear to work
with Cout=18, Rp=10K, F=29.5 MHz.
Suggestions?
jeff
----- Original Message -----
From: "jeff millar" <jeff@wa1hco.mv.com>
To: "Peter Chadwick" <Peter_Chadwick@mitel.com>; "Randall D. DuCharme"
<randyd@specent.com>; <amps@contesting.com>; <W8JI@contesting.com>
Sent: Tuesday, October 17, 2000 1:20 AM
Subject: Re: [AMPS] Series Tuned Tank?
>
> I was able to confirm that a series cap increases Q and several
> people helped me to understand intuitively what it works that way.
>
> When I model a series L, the results also show an increase in Q,
> by a lot more than with the series cap. But, there's a lot of options
> for values. After hunting around for a while and not finding a mix
> that works, suggestions are welcome.
>
> What should the series L have for a value? I'll model and post the
> results.
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