DC interfering with high-frequency digital signal?

[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.

 

[VWWall]

DrewL wrote:

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.

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.)

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.

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

--
Virg Wall

 

[VWWall]

DrewL wrote:

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.

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

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...

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!

--
Virg Wall

 

[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...

 

[VWWall]

sparky wrote:

? "VWWall" <vw...@large.invalid> ?????? ??? ??????news:XoWdncTJufdb2MnVnZ2dnUVZ_u6dnZ2d@earthlink.com...

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;-)

But it wouldn't be OFHC Copper!

And sound at least as good !

Some interesting observations:

From: http://www.roger-russell.com/wire/wire.htm#oxygenfree

"...So what do our fifty hours of testing, scoring and listening to
speaker cables amount to? Only that 16-gauge lamp cord and Monster cable
are indistinguishable from each other with music and seem to be superior
to the 24 gauge wire commonly sold or given away as 'speaker cable.'
Remember, however, that it was a measurable characteristic--higher
resistance per foot--that made 24 gauge sound different from the other
cables. If the cable runs were only 6 instead of 30 feet, the overall
cable resistances would have been lower and our tests would probably
have found no audible differences between the three cables. This project
was unable to validate the sonic benefits claimed for exotic speaker
cables over common 16-gauge zip cord. We can only conclude, therefore,
that there is little advantage besides pride of ownership in using these
thick, expensive wires"

--
Virg Wall, P.E.

 

[sparky]

On Jun 15, 7:02 am, "Tzortzakakis Dimitrios" <no...@nospam.void>
wrote:

? "VWWall" <vw...@large.invalid> ?????? ??? ??????news:XoWdncTJufdb2MnVnZ2dnUVZ_u6dnZ2d@earthlink.com...



DrewL wrote:
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.

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

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...

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;-)

And sound at least as good !

--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
hordad AT otenet DOT gr- Hide quoted text -

- Show quoted text -

 

[VWWall]

google@woodall.me.uk wrote:

On Jun 16, 6:35 pm, "goo...@woodall.me.uk" <goo...@woodall.me.uk
wrote:
On Jun 16, 12:58 am, VWWall <vw...@large.invalid> wrote:> sparky wrote:
? "VWWall" <vw...@large.invalid> ?????? ??? ??????news:XoWdncTJufdb2MnVnZ2dnUVZ_u6dnZ2d@earthlink.com...
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;-)
But it wouldn't be OFHC Copper!
And sound at least as good !
Some interesting observations:
From:http://www.roger-russell.com/wire/wire.htm#oxygenfree
Ah. But they weren't using one of these power leads ;-)

http://www.psaudio.com/products/xstream_ultimate_overview.asp

Or perhaps one of these:
http://www.needledoctor.com/Tara-Labs-ISM-The-ONE-AC-Power-Cable

I can't believe there's more than one company doing things like this
(or is it all an elaborate April fool?)

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."

--
Virg Wall

 

[google@woodall.me.uk]

On Jun 16, 12:58 am, VWWall <vw...@large.invalid> wrote:

sparky wrote:
? "VWWall" <vw...@large.invalid> ?????? ??? ??????news:XoWdncTJufdb2MnVnZ2dnUVZ_u6dnZ2d@earthlink.com...
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;-)

But it wouldn't be OFHC Copper!



And sound at least as good !

Some interesting observations:

From:http://www.roger-russell.com/wire/wire.htm#oxygenfree

Ah. But they weren't using one of these power leads ;-)

http://www.psaudio.com/products/xstream_ultimate_overview.asp

Tim.

 

[google@woodall.me.uk]

On Jun 16, 6:35 pm, "goo...@woodall.me.uk" <goo...@woodall.me.uk>
wrote:

On Jun 16, 12:58 am, VWWall <vw...@large.invalid> wrote:> sparky wrote:
? "VWWall" <vw...@large.invalid> ?????? ??? ??????news:XoWdncTJufdb2MnVnZ2dnUVZ_u6dnZ2d@earthlink.com...
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;-)

But it wouldn't be OFHC Copper!

And sound at least as good !

Some interesting observations:

From:http://www.roger-russell.com/wire/wire.htm#oxygenfree

Ah. But they weren't using one of these power leads ;-)

http://www.psaudio.com/products/xstream_ultimate_overview.asp

Or perhaps one of these:

http://www.needledoctor.com/Tara-Labs-ISM-The-ONE-AC-Power-Cable

I can't believe there's more than one company doing things like this
(or is it all an elaborate April fool?)

Tim.