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Old March 18th 17, 02:32 PM posted to
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Posts: 472
Default TV system conversion

On Sat, 18 Mar 2017 14:38:44 -0000, "NY" wrote:

"Graham." wrote in message
.. .
I think you've already seen this, and I must redo it sometime, now I
have built a Band I modulator and the picture is miles better.
An obsolete PC with webcam running Vidblaster and WinModelines, which
coaxes half the dual-head graphics card to output 405 lines (or 625 or
813, 525 etc.)

It's still not a real-time system converter, but I question why anyone
would want one, I am perfectly content to digitise analogue TV content
first and import the resulting digits.

Excellent bit of work.

I notice you're getting some 1Hz beating between the pictures on the TV and
your video camera for making the Youtube video. I've just looked at the
"Stats for Nerds" and I see that you shot your Youtube video at 24 rather 25
Hz, so that's why! Maybe in the interests of perfection you should use a
normal 25 Hz camcorder next time :-)

I don't know, but I didn't think *that* was the problem.
I was using an iPad. I notice that Big Clive has abandoned his iPad,
he was forever complaining about flicker and lack of control, and is
using something different now and has other problems noticeably with
What I thought was the problem was the crude arrangement I had to
inject the video into the set.
I hadn't finished restoring the set, and I had not built a modulator,
so I injected the video onto the grid of the video amp. As I no longer
have a suitable isolation transformer to power the set I used a cheap
UPS and a 12v 20A PSU as an inverter to provide 230V isolated from
earth. The UPS uses a ceramic resonator as its frequency reference.
The UPS output was not true sign-wave and was far from ideal, There
was some visible hum present,

Before the National Media Museum got rid of their TV gallery (a criminal
waste to consign all the equipment that had on show to behind-the-scenes
tours only) they had three screens showing the same recorded pictures:
405-line, 720x576 SD and 1920x1080 HD. I wonder whether they used similar
equipment to you for down-scaling the HD original to 405-line mono, either
via a modulator or a direct tap into the composite video feed within the TV.

I do wonder what planet the National Media Museum are on: first they got rid
of the excellent Tim Hunkin "how TV works" demos, then the Calendar News
studio showing the petrol fire in Summit Tunnel, and all the
behind-the-scenes work to produce a live news programme, and now they have
got rid of most of the TV gallery. What will be left? The still-photography
gallery (which is still good), lots of stuff aimed at children who just like
w**king the buttons, and a few temporary and slightly pretentious galleries
of various photographers' work. Last time I went (before the demise of the
TV gallery) I was fairly underwhelmed, and I bet I would be even more so

It's a shame that when the Museum of the Moving Image on the South Bank in
London closed, more of the displays from there didn't find themselves at the
Bradford museum.

A friend of mine donated a Dynatron to the Vintage Wireless Museum in
South London.

I suspect they use the de facto standard device viz the Aurora
standards converter. All that will do is convert from 625 and show a
factory set stored still, usually a test card.

It seems to me that my rig would be far more flexible for a museum,
and I would like to run them side-by-side to see if my picture quality
matches that of the Aurora.