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DC interfering with high-frequency digital signal?

D

DrewL

I need to run 250 ft. of 2 cables, and they have to be right next to
each other. I'm trying to figure out if low-voltage DC electric
interference will be an issue. Hopefully the following data is
sufficient:

Cable 1: twisted pair
15VDC at 13W
2 conductors, 16AWG: stranded bare copper, radius=0.645mm, resistance
4ohm/1000ft.

Cable 2: Coaxial
18AWG conductor: solid bare cooper, radius=0.51mm, resistance 6.4ohm/
1000ft.
Full copper braid and foil Shield: see full specs for VSD2001 in
http://www.gepco.com/products/proav_cable/video/coax_hd_sdi_F.htm

The signal is SMPTE 292M, a.k.a. HD-SDI, carrying 70mA of 800mV peak-
to-peak, at 1.5Ghz. More detail in http://en.wikipedia.org/wiki/HD-SDI
.. I know the coax alone is fine, since the manufacturer certifies it
for 300-560ft. of HD-SDI.

I'm not expecting anyone to delve into the HD-SDI specs to figure out
exact error tolerance, I just hope to get an idea of whether I should
be worried or not. Should I go to lengths to get a shielded version of
cable 1?

Any insight is appreciated.
 
D

DrewL

DC doesn't radiate! No problem. Even if the DC is "noisy" the co-ax
shielding should be adequate.

That sure makes it all sound easy :)
I do plan to use the most expensive DC power supplies I can find -
ones for laptops - so for the sake of my signals and the expensive
equipment they'll feed, I hope they will behave.
You don't need to twist them and solid 14AWG solid might be cheaper.
(With the price of copper going up, the #16 might be cheaper, but it's
not a standard gauge for power wiring.)

I have plenty of twisted & stranded 16 AWG in stock (speaker wire), so
costing an extra $0 makes it the cheapest and preferred choice...
 
T

Tzortzakakis Dimitrios

? "VWWall said:
These may be expensive for other reasons than quality. There are many
excellent 15V power supplies on the market.


Free is always cheaper than anything else! My point was you don't need
the twist or the stranded and 14AWG is availably extensively.

Don't let monster Cables know you're using #16 for speakers! :)
Even if he was using #10 it would be cheaper than monster cable;-)
 
T

Tzortzakakis Dimitrios

? "VWWall said:
The audiophile community seems to have a adequate supply of fools,
regardless of the month! There's a more than adequate supply of those
ready to fool them, if only most of the time.

Where else is a complex signal transmitted and replicated many times
through non-linear systems, accessed by a non-linear human ear, and
evaluated by the most complex element of all, the human brain?

No wonder there's room for fools! "Send in the clowns."
$140 a foot? For $2bn you have a custom nuclear power plant, (1.3 GW,
impulse current 100 kA at 400 kV)with enough wattage to satisfy even the
more power hungry stereo maniac! Complete with OFC wiring right to your
receptacle. I thought that somebody would think of special plug cables!
(PS see in this videoclip in you tube an interesting song by OMD with some
disconnect switches closing
)
 
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