[Argus25]

There are good reasons why the interlace in the TV22 is poor. Most of the explanations for poor interlace overlook the obvious. Mechanisms such as the V osc triggering on H pulses etc are invoked.

But the primary cause, of the poor interlace in the TV22 (actually like many pre-ww2 sets) is two things, that both happen together, namely over integration of the sync pulses (it loweres the level) and too low a level of sync pulse injection to the V osc.

If you look at the TV22 after the unnecessary diode they have there, you will notice the time constant of the vertical integrator components are outrageously long, with values such as 100K and 0.01uF when really the values should be more like 0.005uF and 10k, so it out by a factor of 20, yes that bad. This is why there is poor interlace.

An ideal time constant for a vertical integrator (to extract the V sync but without serrations from H sync, yest still producing a vertical separated pulse with a fast rise) in a two stage filter has a time constant of 50uS. So typically the filter should be a series 10k resistor and 0.005uF to ground then another series 10K and 0.005uF to ground and Bob is your Uncle.

PS , for a two section filter, the time constant is R1(C1 + C2) + R2C2.