Re: Gap turn off at zero current and TVI
>> / \ I spoke to a friend in the TV business
>>! . . . . . . . ! and he told me that one TV scan line in
>>! ! the UK is 56us. Therefore, the 23 dots
>>! . . . . . . .! in each line indicate that the source of
>>! ! interference is pulsing every 2.43us for
>>! . . . . . . . ! roughly the duration of one line (56us.)
>>!. . . . . . . ! The 2.43us corresponds to a repetition
>> \___________________/ rate of 411 KHz. Now for the surprise.
>>The resonant frequency of my TC is 206KHz. (Half the repetition rate
>>of the interference bursts !) At first I thought this was a mere
>>coincidence so I removed a toroid, and retuned the TC to a higher
>>frequency (280KHz). Guess what ? This time there were 31 dots per
>>horizontal line !
>>In summary, if you look really closely at the primary damped current
>>oscillation there are very intense bursts of very high frequency RF
>>at each zero crossing. Since there are two zero crossings per cycle
>>this explains why the dots on the TV appear at twice the resonant
>>frequency of my TC primary circuit.
>Neat!!!! This is really the first definite time anyone else has confirmed
>the zero crossing bursts!! Of course, you are right! This would give
>bursts at DOUBLE the Fo frequency!!!! Excellent discovery!!!!!! Very
More likely, you are seeing the RF power emitted by the sparks at the
"peaks" of the waveform, not the zero crossings. You'll get a spark (or
corona, or whatever) on the peak, regardless of the polarity.
You can probably determine any effects from interlace or overscan by looking
at the shift in the dots from line to line as you go down the screen. If
the dot rate is an exact multiple of the horizontal line frequency
(525/59.94 in US, about 625/50 in UK), the dots will line up in vertical