>>>>? RL depends on the ZSAC.
? (Zero Signal Anode Current)
>>>>With higher idle current, RL decreases.
>>>>Using RL=DCV/2 x I-anode, at 0.8A, RL=3.125k-ohms. Designing for a Q of
>>>>15 at 28MHz, a Pi-L with an intermediate Z of 300-ohms, XC1=208 ohms,
>>>>C1=26pF. L1=1.5uH. L2=0.64uH. C-load=129pF. Subtracting 10pF for the
>>>>C-anode + stray C, C-tune is 18pF. The min. C of a UCS-300 is 5pF. Have
>>>>I missed something?
>OK, so I owe you a pizza!
? ok. If you are ever in the area, we could do lunch.
>Some guys use a 1.8 number as the multiplication factor for I-anode.
? With an 8877, or a similar triode, so would I.
>No matter, it still is much less than the 4600 Ohms I was using.
>Using your formula, the 4600 Ohms assumes an I-anode of c.500 mA.
>OK, so answer this then: Why am I having problems matching on 10m?
? I would have to measure some things to figure it out.
>Why does my power output top out at 800 Watts? Once I get over 60 watts of
>drive, I get no more power out no matter what I do.
? Sounds like a tuned input problem. What is C1?
>In looking at everything I was assuming it was becasue Q was too high.
>What light can you shed on this?
>Also, how do you determine your peak anode current.
? look at the constant-current characteristic curves. For good
linearity, pick the highest peak-current curve that has a defined knee at
the anode/plate potential equal to the screen-supply voltage. For the
8166/4-1000A, the highest such curve is 2.6 peak-amps. Divide
peak-current by 3 to obtain avg. current. This is how I arrived at the
c. 0.8A figure.
>The current will
>change depending on what amount of drive you have applied to the amp. So
>I what I think you are saying is that you would need to drive the amp so
>that the plate current is at 0.8 A. But then if you decrease the drive,
>you would change the impedance and hence the match. Correct?
? yes x 3. The guy who wants to take it easy on his linear amp. and
tunes up with reduced drive, gets a mistune every time. . .
- cheers, Jon
R. L. Measures, 805-386-3734, AG6K, www.vcnet.com/measures
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