Re: Kramer VDAs

"William Meyer" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> oN 10-Nov-03, Cameron Dorrough said:
> 
> > What should I be looking for in a broadcast VDA (apart from the
> > obvious like Gain & EQ control)??
> 
> In a broadcast VDA, gain controls are standard; EQ controls are not.
> Generally, EQ is found only on equalizing VDAs, and then it is
> specified as tailored to a particular cable type, and generally for up
> to 1000 feet of that cable.
> 
> These days, most ordinary VDAs will probably be using the Elantec VDA
> chips (and if they don't, the question should be asked: why not?) If
> this is so, then it's very easy to achieve good performance.
> 
> I see on Kramer's site that their 104L VDA is specified as having a
> 420MHz bandwidth. That's much more than needed, and while it's good to
> have >60MHz bandwidth, going much beyond 100MHz is of questionable
> wisdom, and can create other problems (sensitivity to RF pickup,
> tendency to oscillate, higher noise floor, etc.)

> snip
> > In VDAs, as elsewhere, you get what you pay for. The cost of VDAs is
> generally a small percentage of any system cost, but the faults that
> can result from prefering low cost over quality almost inevitably
> qualify such decisions as short-sighted, at best.

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?

Thanks,
Rick