An interesting CCTV problm... any ideas?

[SH]

Right I have an analogue CCTV system comprising of 8 cameras.

We'll number them as Cam 1 to Cam 8 to help with describing the problem.

They are all powered with 12 V dc from a proper CCTV power cabinet:
https://www.tlc-direct.co.uk/Products/TSPSU16slash20.html which is next
to a 8 channel Samsung SRD870DC DVR.

The cable used is this:
https://cpc.farnell.com/pro-power/ca-sel-07m100/security-cable-black-100m/dp/CB02516?st=CCTV

So the yellow co-axial is used for video and the red and black wires
used for 12V DC. There is an outer foil screen on the CCTV cable.

Now Cam 1 and cam 2 are at the front of the house.

Cam 8 is at the back of the house. Their respective cables run for about
a metre before cam 8's cable branches away from the cables for Cam 1 &
cam 2.

Cam 1 is looking at the front lawn.

Cam 2 is looking at a car with alloy wheels on the front driveway

Cam 8 is looking at a vegetable patch in the back garden which has a
picket fence around it.

On the TV sets when selecting Cam 1, I am seeing a horizontal scrolling
ghost image of cam 8 on here it looks like a grey pencil drawing of all
the edges of of the slats of the picket fence slats across what is the
front lawn.

So something from Cam 8 is getting into Cam 1

On the TV sets when selecting Cam 8, I am seeing a scrolling ghost image
of what lloks like a grey pencil drawing of all the edges of my car with
the allow wheels scrolling across of what is the vegetable patch.

So Something from Cam 2 is getting into Cam 8.

I have already tryed unpplugging cam 1 from the DVR and plugging into
another camera input. the problem is still there

I also have tried unplugging cam 8 from the DVR and tried it in another
camera input. the problem is still there.

So it does not appear to be video cross talk from within the DVR.

I have a bank of 10 UHF mods, I have already tried turning these off and
unplugging the video leads between this UHF bank and the DVR, the
problem remains so it is not video crosstalk across the 1o UHF modulators.

I have another theory but would like to open to the floor what the
audience think?

[Indy Jess John]

On 06/01/2022 17:43, SH wrote:
> Right I have an analogue CCTV system comprising of 8 cameras.
>
> We'll number them as Cam 1 to Cam 8 to help with describing the problem.
>
> They are all powered with 12 V dc from a proper CCTV power cabinet:
> https://www.tlc-direct.co.uk/Products/TSPSU16slash20.html which is next
> to a 8 channel Samsung SRD870DC DVR.
>
> The cable used is this:
> https://cpc.farnell.com/pro-power/ca-sel-07m100/security-cable-black-100m/dp/CB02516?st=CCTV
>
> So the yellow co-axial is used for video and the red and black wires
> used for 12V DC. There is an outer foil screen on the CCTV cable.

<Remainder read then snipped>

I have a CCTV system with 7 cameras. The recorder is a Floureon, and I
have powered the recorder and cameras sharing the load over three power
supplies so that I don't overload any of them, and I have bought CCTV
cables of fixed lengths with made-up ends to connect cameras of various
makes to the recorder.

I notice that when the cameras switch into night mode, they seem to have
more than one IR frequency, and I have had to be selective about which
ones point in which direction so that I don't get any areas over- or
under-illuminated. What I don't get is any cross-talk between cameras,
like you have reported.

The key difference I see between my set-up and yours is the recorder to
camera cable. You only refer to using the red, black and screened
yellow, and I wonder if the unused cores are creating the cross-talk in
the metre or so where all the cables run in parallel? You will also
have a bit of wire separation because the power is from a box and the
signal goes to a nearby recorder. You don't give measurements but I
would guess the separated runs are considerably more than my pre-formed
cables which only have 10cm of separate tails. What do you do with the
blue, green and white cores at the point of separation?

If the screen to the yellow cable doesn't screen 100%, then the blue,
green and white cores could be radiating the signal. Have you tried
soldering these unused wires to the yellow screen at both ends in every
connection?

Jim

[williamwright]

On 06/01/2022 17:43, SH wrote:

> Right I have an analogue CCTV system comprising of 8 cameras.

Crosstalk via the camera PSU? Try powering a cam that is giving
crosstalk from a battery.

Bill

[williamwright]

It the camera or recorder didn't perfectly match the cable there could
be signal voltage on the coax screen that jumps onto the red/black.

Also not all co-ax is 'leak-proof'.

Bill

[Brian Gaff (Sofa)]

Power supply intermodulation, ro maybe the signal levels in the cables are
high enough to cause it no matter what you do, unless they are completely
separated?
Brian

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[SH]

On 07/01/2022 09:44, Brian Gaff (Sofa) wrote:
> Power supply intermodulation, ro maybe the signal levels in the cables are
> high enough to cause it no matter what you do, unless they are completely
> separated?
> Brian
>

If there was PSU intermodulation, would you not expect all 8 cameras to
be affected and how does that allow a ghost image from one camera to get
into another?

I am wondering if a 0v black wire has become disconnected somewhere do
DC ground is now being provided via the co-ax outer screen?

[SH]

UPDATE!

The common denominator appeared to be Cam 8 as as something from Cam 8
was getting into Cam 1 and something from cam 2 was getting into cam 8.

So I went to Cam 8, and unplugged the DC power. I then replugged it and
moved it up and down it in case of resistive contact to "clean" the
contacts in both the socket and plug.

Lo and Behold, the problem has now gone!

I can only assume that it was a bad DC ground and that the outer screen
of the co-ax then ended up providing the DC ground to Cam 8 as it had
carried on working......