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Author Topic: Needing info and help for multiple wired SC23A cameras  (Read 22889 times)

Noam

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Re: Needing info and help for multiple wired SC23A cameras
« Reply #30 on: November 29, 2011, 10:00:34 AM »

Noam's quick fingers beat me to this and we are  thinking along the same lines, so I will post anyway
YES! I think this is one of the first times I've beaten one of the "regulars" to the punch! (that has been acknowledged, at least ;))

Quote
The ringing is likely caused by multiple RJ45 connections. Each conection can cause a reflection, especially if there is a layer of oxidation on the pins. The "foggyness" is loss of high frequency content in the video signal (edge definition). Also the flat cable is much more prone to interference and cross talk than twisted pair. If your flat cables are run by themselves and not near the other flat cables, Romex, or flourescent lighting fixtures, etc. you probably do not have much induced interference. Long runs of flat cable is not good for video, but it is cheap.

I wonder if switching over to CAT5 (or maybe even Shielded CAT5) closer to the camera might make any difference in reducing the noise on the wire.
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MD Corie

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Re: Needing info and help for multiple wired SC23A cameras
« Reply #31 on: November 29, 2011, 11:01:42 AM »

I'm no expert here, but I'm wondering if part of the signal problems (degradation and/or "ringing") might be due to crosstalk from the power supplies over a long cable run. Since the cables are not shielded, other electrical noise along the way can also degrade or interfere with the camera image. ...

That is a definite possibility - perhaps even a probability in this case... although I believe the ringing aspect is caused only by reflections, not so much by interferences.  I suppose the proximity to certain materials could cause reflections by affecting the characteristic impedence of the line, but... ???

If the "stock" camera, connected directly to the monitor (with NO home-made cabling or junction boxes) does not produce a perfect image, then perhaps there is something wrong with the camera. Have you done this test with more than one of your cameras?
Well, define "perfect image"...  ;)   In my opinion, the cameras are not all that great to begin with.  And, yes, I've tested each and every camera stand-alone upon delivery, and they're all pretty much the same.

I don't know if it is the same for the wired cameras, but I seem to recall with my wireless ones (which I sold, so I can't check them anymore) that the lens rotated to help focus the image. Perhaps yours are actually out of focus, and that might be adding to the problem.
Supposedly, they do... but I have not been able to adjust them in any way that provides much improvement in the images.

It sounds to me like you probably have a number of factors working together to give you a less-than-stellar image at the end. There may be no single fix that will take care of it all.
That is likely true.... and that's why I was trying to focus only on the ringing aspect (because that seems to have a relatively significant impact on the "viewability" of the images - such as they are).
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MD Corie

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Re: Needing info and help for multiple wired SC23A cameras
« Reply #32 on: November 29, 2011, 11:11:57 AM »

The ringing is likely caused by multiple RJ45 connections. Each conection can cause a reflection, especially if there is a layer of oxidation on the pins. The "foggyness" is loss of high frequency content in the video signal (edge definition). Also the flat cable is much more prone to interference and cross talk than twisted pair. If your flat cables are run by themselves and not near the other flat cables, Romex, or flourescent lighting fixtures, etc. you probably do not have much induced interference. Long runs of flat cable is not good for video, but it is cheap.
RJ45?  You mean the modular connectors?  Yeah, I would assume that connectors are a likely source of reflections, although I don't imagine there is a lot of oxidation on the gold-plated contacts - especially with all the disconnecting and re-connecting that I've done lately, that would tend to "wipe" the contacts.  ;)

The HF loss must exist in the cameras or their own cables...  The only "flat" cables that may exist in my "network" would be if the camera cables themselves are "flat";  the Cat-5e is 4x twisted pairs.

If "external" interference can cause the ringing, then that's worth looking into.
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MD Corie

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Re: Needing info and help for multiple wired SC23A cameras
« Reply #33 on: November 29, 2011, 11:18:58 AM »

I wonder if switching over to CAT5 (or maybe even Shielded CAT5) closer to the camera might make any difference in reducing the noise on the wire.

In theory, it should... but, of course, that would only be worthwhile if the problem is due to external noise sources.

I'm not sure what all the manifestations of external noise may be as far as the video image is concerned, so I'm not sure whether what I'm seeing is due to external noise... but there is nothing in particular that I am aware of that indicates external noise is a significant problem here.  (What should I look for?)
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