PAUL HEWITT
WD7S PRODUCTIONS
QRO HOMEBREW COMPONENTS
http://wd7s.home.att.net
> Wrong, Kimo-Sabe!
> The Eimac data sheet plainly states that typical performance
> (measured data) to 30 mhz that the cathode input impedance
> is 24 ohms. It also states that a resonant input circuit should be
> installed at the cathode, and it is to have a Q of 5 or MORE. This
> assumes an anode RL of 1000 ohms.
Using Eimac's characteristic curves in a software generated Chafffe
analysis all for class AB2:
6000v @ 14000w=30 ohms cathode impedance
6500v @ 12000w=23 ohms
5000v @ 10,000w=19 ohms
Driving impedance depends greatly on operating conditions.
I think I said this
Most 3CPX5000's I have seen are around 18-20 ohms.
> For folks that would go to all the trouble and expense to put
> one of these tubes and then operate it at reduced output, a
> few bucks more will buy you a tuned input circuit with a roller
> coil and two variable caps.
While impedance matching can be accomplished many ways, the
most important improvement of using a tuned input is realized
when the tuned input proveds a very low impedance at the cathode
for harmonics of the operating frequency, especially the low-order
harmonics.
That means where ever and how ever the tuned input is located,
impedance measurements from the cathode looking back at that
network should show a virtual short at harmonics of the operating
frequency.
73, Tom W8JI
W8JI@contesting.com
Do you know what values were used to establish the load line used in your
Chaffe analysis?
With fixed tuned input networks, "ballpark" figures are of no use.
Thanks, Paul
PAUL HEWITT
WD7S PRODUCTIONS
QRO HOMEBREW COMPONENTS
http://wd7s.home.att.net
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