>From the 30S-1 Manual
INPUT CIRCUITS
Pi-network broad-tuned circuits and the interconnecting r-f feed line match
the 50-ohm input impedance to the cathode impedance, which is approximately
100 ohms. The 20.5-foot length of cable (furnished) is necessary between the
32S-1 (or KWM-2) driver and the 30S-1 input circuits. This is due to the
necessity of having an even multiple of 180-degree phase shifts between
driver plate and power amplifier grid. The cable length and the 30S-1input
circuits together accomplish this. An even multiple of 180-degree phase
shifts is necessary because modulation components cause a change in the
resistive PA cathode impedance which is translated to a shift in reactive
impedance at the driver plate. The shift in reactive impedance, at the
driver plate, results in phase modulation of the driver and increases the
total over-all distortion of the system. A 2.5-foot additional length of
cable is furnished to bring the total interconnecting cable length to 23.0
feet for use with the KWM-1 as a driver. Drive power required for maximum
legal input on SSB is 80 watts PEP.
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