Howdy all.
Got a question on my 4-1000A. What should the input impedance of this
tube be? I have heard that it is approximately 110 Ohms in parallel with
27.2 pf.
My problem is that I had build an input network to match to that
impedance. Everything seemed to be working fine. Suddenly however
though, the impedance changed. The matching networks no longer gave good
SWR. I can match up the amplifier with a match box and get full power out.
All the components in the input path of the amp are fine. Today I have
been playing with this tube (bought it about a month ago from Surpluss
Sales of Nebraska) and with an old 4-1000A that was going bad (which is
why I got the second tube). The old tube appears to have the impedance I
have expected or at the very least different from the newer tube.
I've managed by trial and error to match up 80 meters and 40 meters. I
am using an L-network (series L/shunt C - lowpass configuration). Both
circuits take larger inductors and smaller caps than I had expected. I
am still working on 20, 15 and 10.
Is there something wrong with this newer tube? Did I do something to
damage it? Do different tubes have different impedances and/or can this
change over time?
Should I not use this tube and stop working on the circuitry that I am
working on or is everything OK. Do I need to get a new tube (again!)?
If I need to get a new (or different tube) where can I get one cheaper
than what they sell them for at Surplus Sales of Nebraska?
I don't know if I am making myself clear here or not, so I am describing
it as best as I can.
Can someone please get back to me with anything they know.
73,
Jon
KE9NA
-------------------------------------
Jon Ogden
KE9NA
http://www.qsl.net/ke9na
"A life lived in fear is a life half lived."
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