Help! Interference

[dsw]

Hi guys,

After having a good day at IFSEC yesterday we cracked on with our installation of a PTZ from system Q today. It is mounted on a pole around 7 meters up and runs across wire into the main building. We got it all hooked up, everything working fine except we can't seem to eliminate some interference - sort of waves going diagonaly down the screen. We have tried to keep it away from any mains, re terminated the dvr bnc, and also tried the ptz psu on same mains socket as dvr. Except for re-terminate the ptz bnc we have tried almost everything except for a humbug. After searching through the forum i found an old thread about rfi interference from a local radio tower it got me thinking. I seem to recall our customer mentioning them having problems with telephone lines and broadband and even being able to hear the radio on their telephones. Could this be the cause. This is so frustrating as we have tried everything and the interference ins't that bad.

PSU 24v AC, telmetry cat5, power .75 flex, high quality rg59, 3x wireless GJD opal sensors.

By the way we tested speed dome on bench first with around 10m of cable and it was fine. Cable run is a maximum of 25m. Is it worth trying a humbug.

I know i'm asking alot but any help would be greatly apreciated.

guys

[Guest -Dan-]

Could be rfi, probally ground loop problems!

[ian.cant]

I dont think its RFI although ive never used wireless GJD sensors so they could be the problem.

However in my experience telemetry is run in a screened cable and i would consider that as a possible reason. Does the interference only happen when you try to move the dome as that would be confirmation really.

[dsw]

I don't think it' that. We had the interference before turning on the sensors and receiver. We always use cat5 for telemetry, dome supplier also recommends this too, as far as i'm aware most installers tend to use cat5, moving ptz has no effect on interference, it is constantly on the screen. Thanks for your reply

[ian.cant]

We had the interference before turning on the sensors and receiver.

Well that narrows it down to the dome, DVR or your power supply i would say.

If the video is direct to the DVR have you tried it direct to a monitor 1st?

[dsw]

Yes we have tried it direct to the monitor and still have the same problem. Not likely to be dome as we tested on bench first and was fine but anything can happen during transport spose. It could be the psu but again we tested it before installing on our bench at the workshop. It's a 2.5 amp 24v ac psu. Will have to order another as ive used the last one.

[ian.cant]

I would try ditching the cat5 see what happens. Meter the coax and check for earths, remake bnc, try a humbug, do the obvious on site fault finding.

I doubt its the PSU and it doesnt sound like the dome but i would bench test again before buying replacements.

Last option would be to contact System Q for advice, if anyone has the answer they should!

[dsw]

will call system q tomorrow. will try disconnecting cat5 and redo bnc. should do the trick.

thanks again for your advice.

[Doktor Jon]

From the description, it certainly sounds like an earth loop problem.

Jarv, you mentioned it was mounted on a pole. If there is any earth continuity with the pole itself, that may be causing the problem.

If there is any way of temporarily insulating the camera from its mounting (just for testing), you may find the problem disappears (fingers crossed). This might sound like a silly suggestion, but if you stick the camera in a plastic bucket, the picture may be non existant, but at least you can see if the intereference is no more!

[baywatch]

Why don't you try connecting up a different camera on the pole to the coax only(any camera you have handy) if the interference is still there then you can eliminate the telemetry.

We have had some rf issues in our local area and it can be a big problem to eliminate.