[opendtv] Re: "we'll forever be stuck with by going ATSC"
- From: jeroen.stessen@xxxxxxxxxxx
- To: opendtv@xxxxxxxxxxxxx
- Date: Wed, 12 Jan 2005 12:56:08 +0100
Hello,
Mark Schubin wrote:
> Here's a URL for a SCART cable specified at less than 3 dB
> down at 50 MHz at 100 feet:
> http://www.nordost.com/Cables/video-silver-screen-scart.htm
In 2002 Eric F. and I had a nice discussion with the young
lady of the Nordost stand in the shopping mall in Boston next
to the building where the SID was being held, and she gave us
some of their brochures. This is funny stuff, more so when you
see there prices... (I am in the wrong business here !)
I remember my EMC guru. He told us that people would sometimes
ask him how to improve the quality of a Scart cable. He would
tell them not to bother, because no matter how expensive you
make it, it will still be a crap connection. It has something
to do with the way the core and the shield are terminated as
"pigtails" to separate pins, thereby losing the coaxial
structure. Not to mention the way the signal is subsequently
carried inside the TV (or source), no way resembling a coax
cable. So inevitably any common mode currents will cause a
differential mode voltage interference into the signal...
If you must do anything at all, says I, then at least put some
ferrite rings around the cable to suppress the common mode
currents. And don't send all your money to Nordost et al.
> Do you know of any analog HDTV connections with higher bandwidth?
For the Scart it would be overkill, because it is only an SD
signal requiring 5 MHz bandwidth or so. There once existed a
"Golden Scart" specification by Thomson, for analog HD signals,
and that would carry somewhere between 20 and 30 MHz bandwidth.
It used the same physical plug, but in a yellow-gold colour.
But that standard for HD is long dead, having been replaced
with YPbPr over triple cinch and VGA over DB15 (and later HDMI).
Interference is much more of a problem than bandwidth,
especially with the unshielded (!) thin Scart cables that are
sold in some places for very little money. If you happen to
run such cable close to a deflection circuit or switched mode
power supply, then you'll pick up everything...
No, the best analog connection by far is still with good
quality coax cables terminated in BNC connectors. And even
then you would still have to worry about ground loops, etc.
The ideal link for the future is an optical digital link,
with at least 10 bits per pixel and 4:4:4 signal of course.
Or... no external link at all, by integrating the receiver
with the display. That's a lot cheaper.
Best regards,
-- Jeroen
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| From: Jeroen H. Stessen | E-mail: Jeroen.Stessen@xxxxxxxxxxx |
| Building: SFJ-5.22 Eindhoven | Philips Digital Systems Laboratories |
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