A single 811 usually has a cathode Z of about 200 ohms, so three in
parallel would be 67 ohms and put that in parallel with 150 ohms makes
50 ohms.
The low pass filter has the only reactive components in the circuit, so
there must be a problem with it. I presume its the replacement filter
that passes 10 meters and I don't have the diagram for it.
73, Jerry, K0CQ
On 6/1/2010 11:42 AM, CSM(r) Gary Huber wrote:
Ooops, I should have stated the input resistor as 25W at 150 Ohms. Still it is
in parallel with the cathodes of the THREE grounded grid 811s, so the input SWR
should be 3:1 or less when the source impedance is 50 Ohms. Calculate the
needed coax length (between the source and load) by multiplying the velocity
factor of the cable times the electrical wavelength of the frequency of
operation.
Manual at:
http://www.tentec.com/files/Model%20411%20Centaur%20Owner%20Manual.pdf ....
Input schematic, manual page 5-8 (PDF page 43)
73,
Gary - AB9M (just a Ham doing applied electronics)
|