 100* / 1% change in Cathode Voltage
 10* / 1% change in Grid "on" Voltage
 0.0005* / 1% change in Collector Voltage
These numbers are approximate. The actual values of phase pushing for any specific TWT are determined by gun perveance, gain, efficiency, etc. Any periodic voltage modulation produces signal side bands, separated from the main signal by the modulation frequency. The depression below carrier of these spurious signals (* in dB) for sinusoidal ripple can roughly be approximated by the following expression:

A ±0.5 volt sinusoidal ripple on a 10 kV TWT with 10" inputtooutput length produces 49.5 dBc sidebands at 10 Ghz. Peaktopeak phase ripple (** in degrees) is directly related to small signal gain ripple (dG  peaktopeak in dB) by the following expression:
A small signal gain ripple of ±0.2 dB produces phase ripple of *1.35*. Time delay is the total time it takes for a signal to pass through the tube (typically 3 to 5 nsec) and is the derivative of phase delay. Thus, the same mechanisms that cause phase nonlinearity are responsible for time delay distortion. The maximum rate of change of time delay (** in nsec / Mhz) due to gain and phase ripple is calculated by:
where dF is the frequency periodicity of the small signal gain ripple (in Hz). A 200 Mhz gain ripple with ±0.2 dB amplitude causes 3.7 psec / Mhz time delay distortion.