In message <firstname.lastname@example.org>,
Frank Donovan W3LPL <email@example.com> writes
>A class B amplifier produces many harmonics as it switches from
>conducting to non-conducting, and the input tuned circuit must provide
>an excellent input termination impendance not only at the fundamental
>frequency, but also at the 3rd harmonic and ideally at the 5th harmonic
>as well. This would not be a problem if it were a Class A amplifier,
>but that's certainly not practical for a high power RF amplifier!
>Even a short piece of RG-58 between the input tuned circuit and the
>tube socket significantly increases the input termination impedance at
>the harmonic frequencies.
I'd guess that the phase changes the cable introduces at harmonic
frequencies has a lot to do with it. The loss in a foot of RG58 even at
150MHz is small.
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