Interference

[Ben Ritchie]

I've just picked up a combined power + BNC cable to connect my Watec to a TV in the observatory, like this one but in 5M length

http://www.ebay.co.uk/itm/10M-BNC-CCTV-SECURITY-CAMERA-VIDEO-POWER-EXTENSION-CABLE-LEAD-/280952705426?pt=UK_CCTV&hash=item416a161192

but when I try and use it I see pronounced diagonal banding. I think this must be because the power and signal run together, because if I use a separate power supply the BNC connection seems fine and there's no interference (i.e. it's not just a dodgy BNC cable). Likewise if I use a different BNC cable but this power connection the signal is also fine, so it's not the power connection causing problems with the Watec. So I assume it's just a cheapo unshielded connection or something that's the cause of my problems?

If so, does anyone have recommendations for better quality cables? Running both together is nice as it cuts down on the cable spaghetti, but not if it causes interference in the process...

[Macavity]

The main problem with "better" power / signal combi leads, is their quasi-RIGIDITY

- Particularly at low temperatures?

The shielding of my (nice, thin, flexible!) cables proved inadequate too though - As you say, presumably due to close proximity of the signal and power leads. I eventually found it was ALSO associated with the inherent "noise" on the observatory power lines, originating with a trickle charger for the deep cycle battery.

The Watec Camera documentation implies need for a stable (not necessarily stabilized) 12V - But e.g. p/m 10% etc. supply. So I added one:

A 12V (car / automotive) 15-19V Laptop "up-converter" (Set to 15V, for "headroom") THEN stabilised / smoothed, with a classic (home-brew) 7812 regulator circuit - Added, tantalum, capacitors etc. With a nice CLEAN 12V line, to the camera, there seemed no further problem with the barring. Even with budget (flexible) cable and charger running.

A slightly circuitous (no pun), slightly crazy(!), idea - But an effective solution in my own case. Copes well with my personal concern re. the fully-charge (13-14V) battery over-voltage to the Watec. Took ages to locate the real origin of the "random" [charger] noise tho'...

[Carl Reade]

I've just picked up a combined power + BNC cable to connect my Watec to a TV in the observatory, like this one but in 5M length

http://www.ebay.co.u...=item416a161192

but when I try and use it I see pronounced diagonal banding. I think this must be because the power and signal run together, because if I use a separate power supply the BNC connection seems fine and there's no interference (i.e. it's not just a dodgy BNC cable). Likewise if I use a different BNC cable but this power connection the signal is also fine, so it's not the power connection causing problems with the Watec. So I assume it's just a cheapo unshielded connection or something that's the cause of my problems?

If so, does anyone have recommendations for better quality cables? Running both together is nice as it cuts down on the cable spaghetti, but not if it causes interference in the process...

Sounds like either poor screening or the power source is putting out a certain amount of RF as well as voltage. A 12 Volt battery cannot produce interference and is a clean power source.

One option is to use a twisted pair phone cable which is unscreened and combats interference due to the twisting. Two wires provide the voltage and the other two provide the video signal all down the one cable the same size as RG45. You just need to add a Balun at each end (Look up CCTV Baluns on Ebay very cheap).

Neat and should sort your issue out.

Hope this helps, Carl

[Ben Ritchie]

Thanks, ordered a pair of CCTV Baluns from the ebay so will see if that does the trick

[Ben Ritchie]

Works perfectly, thank you!