[Collins] Re: 30L-1 Tuned Input

[Dr. Gerald N. Johnson, electrical engineer]

The 30L1 manual in the paragraph about aligning the inputs said that 11%
reflected power was the maximum acceptable, 2:1 SWR.

The cathode circuit has a low Q to keep tuning from being too difficult.
If the cathode circuit of a grounded amplifier has a Q similar to that
of the plate the two tuned circuits interact excessively.

The cathode tuned circuit is required to significantly reduce grounded
grid amplifier distortion, but a loaded Q of 1 is adequate. Normally the
output tank has a Q of 12 to 20 (generally higher on 10 and 15 meters as
set by the minimum C of the plate tuning capacitor in parallel with the
output C of the tubes).

There surely are currents at the input of the cathode driven PA that
come from the PA plate current pulses. When the PA cathode is not tuned
they depend on the tuned output of the driver which sometimes can be
damaged by the extra RF.

73, Jerry, K0CQ, Technical Advisor to the CRA.

-- 
Entire content copyright Dr. Gerald N. Johnson, electrical engineer.
Reproduction by permission only.