DIYbanter - View Single Post - TVs compatible, from one continent to the next??

Michael A. Terrell

wrote:

On Jan 10, 3:40 pm, "David" wrote:
"Michael A. Terrell" wrote in messagenews:laidnQF74PTlE7bQnZ2dnUVZ_uWdnZ2d@earth link.com...

??? How can the reference signal correct a differential phase
error?

PLL circuits allowed the signals to remain in sync.

Things will remain in sync but that does NOT fix a differential
phase error in the transmission path. The VIR would adjust the
phase at a mid luminance point, but the differential error still
existed above and below that level.

Even when they built crystal controlled generators, the line
frequency remained close enough that it would take minutes or
hours to
roll though a frame. Also, by the '50s the power supplies were
better
filtered. The hum bars were faint, but visible on older TVs,
and one of
the first signs of trouble when they became more pronounced. A
lot of
US monochrome TVs were transformerless, and used a voltage
doubler in
the power supply. pairs of 300 uF 160 volt electrolytics, where
some
early TVs had 8 or 16 uF filtering.

Color TV changed the field rate to 59.94 Hz and a 120 Hz hum bar
would roll through the picture in under 15 seconds. Even
monochrome broadcasts adhered to the new frame rate.

David

I started working in broadcast TV in '76 at the CBS affiliate in
Madison WI WISC-TV. The incoming signal was a terrestrial microwave
link. There was no differential gain or phase errors on that signal.
When they put up test signals during non-network times they looked
like the signals from the local test generators. SN 60dB and flat
within a fraction of a dB. At the time Madison was market 103 or so so
it wasn't because we were the 'big boys'. The signals in the mid-west
were generally excellent - at least for CBS.

People who never worked in the industry have no clue. They generally
used the cheapest imported TV they could find, then bitched about it.
If they ever saw the video from a TK-46 with a set of new Plumbicons on
a $7,000 studio monitor, they would shoot their digital TVs.

--
You can't fix stupid. You can't even put a band-aid on it, because it's
Teflon coated.