[Amps] Trimming the transmission line

[jeryb77]

>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.