Hi Tom!
Your comments about switching waveform reminds me of a problem I had when
I first built my monoband amplifiers 25 years ago. The higher frequency
amplifiers were less efficient than the lower frequency amplifiers, and
the 10M amplifier in particular was notoriously inefficient (less than
50%) and the tube ran very bright red when transmitting.
To make a long story short, the problem was caused by placing the input
tuned circuit at the rear of the amplifier remote from the 3-1000Z socket.
The connection between the tube socket and the input tuned circuit was
thru aproximately 12 inches of of RG-58/u. Moving the tuned circuit
adjacent to the tube socket and eliminating the RG-58/u interconnecting
cable corrected the inefficiency problem and the tube in each amplifier
runs a nice dull red.
73
Frank
W3LPL
donovanf@sgate.com
On Wed, 23 Apr 1997, Tom Rauch (W8JI) wrote:
>
> Efficiency problems generally are caused by the switching waveform of
> the tube. In grounded grid, the cathode circuit is generally the main
> player.
>
> The cathode's source has to present a low impedance at odd order
> harmonics of the signal frequency, otherwise the tube switches softly
> into conduction. The soft transition actually increases IMD, and can
> greatly lower efficiency.
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