Re: Kramer VDAs

oN 12-Nov-03, Rick Hammang said:

> Bill, very nice way to put it. I have used some, gain only, GV
> multi-card VDA's to adjust levels of various cable runs, by loop
> through. Example, source to transmitter, 400 feet, convidence monitor,
> 10 feet, house distribution 50', and beyond etc., But I'm always
> getting some subcarrier loss at the ends of those longer runs. I
> resorted to equalizing VDA's to bump up the sub carrier, a touch, to
> keep readings preserved. There is plenty more (EQ) gain available for
> the longer runs, like the 1000' that you mention, and I understand
> about the type of precision cable to keep that extra EQ from causing
> problems. In a large facility, several hundred feet could add up
> quickly. Say PCR to router, to MC, on to transmitter etc. Regardless
> of what high quality cable I use, runs exceeding 50'to 80' show a
> slight loss in sub-carrier, longer runs a bit more. Any tips on
> preserving the sub carrier losses, without EQ?

Some years ago, I worked in a sports facility that was badly limited by
building architecture. Cable runs were aggravated by a rigid
requirement to preserve the aesthetics of the structural design. Net
result: to get the feed from a camera in the press box two doors down
from the control room required a link down to the patch room and from
there, up to the press box. Those architectural issues made this two
1,000 foot runs, each of which required an equalizing DA running flat
out to compensate. The reference feed to the camera could tolerate some
loss, so only a single EQ DA was used on that run.

The best way to minimize equalization losses is to use good cable (an
8281 equivalent), and make sure that cables are never kinked, scraped,
or otherwise abused. Take care with installation of BNC connectors, as
well.

BTW, I've demonstrated to doubters in the past that introducing even a
short length (one foot) of RG-59 into a video run produces a measurable
loss. Also note that the characteristic of RG-59 is different than that
of 8281, and that EQ DAs are designed to compensate the 8281
characteristic, *not* the RG-59 characteristic.

-- 
Bill
Posted with XanaNews Version 1.15.7.4