STP vs UTP for Video Surveillance Tutorial

By Brian Rhodes, Published Dec 20, 2017, 10:17am EST

For many video system designers, deciding which ethernet cabling to use is a quick decision: go with the cheapest. However, this overlooks the possibility cable, and the video it carries, needs extra protection against common electromagnetic interference.

STP vs UTP for Video Surveillance

Is the difference between cable types that significant? In this note, we examine shielded cable, look at how it can prevent video problems, and compare it to nonshielded alternatives.

Inside this note, we explain:

  • How Electrical Interference Affects Video Quality
  • What Shielded Cable Looks Like Compared To UTP
  • Physical Differences Between Cable Types
  • Other Names For STP
  • Typical STP vs UTP Costs
  • Use STP Against Common Sources of Interference
  • Practical Use Is Limited, But Axis Disagrees

One Of Many Cable Tutorial Series

This tutorial is one of a number IPVM has addressing the topic of cabling. Others include: Cat 5e vs. Cat 6 for IP Cameras, Cabling Best Practices Guide, Network Cable Testing Guide, Grounding and Bonding for Video Surveillance, and more.

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[****: **** ******** *** originally ********* ** **** and ************* ******* ** 2017]

Comments (24)

Undisclosed Manufacturer #1

12/20/17 04:44pm

Cabling infrastructure properly designed and installed can eliminate a lot of the issues seen in the field with IPVS.  BICSI is the global organization that drives standards and best practices in the structured cabling industry.  If your not familiar with them, they are worth checking out.

Unfortunately a lot of bad habits surfaced when the industry transitioned from analog systems to IP systems.  Installations best practices that worked for RG-6, will not work for UTP/STP systems.  Performance verification is not always required for many IPVS installs, compared to traditional data installs.  Improper pathways, mismatching components, poor field terminations, all contribute to poor IPVS installations.

While I understand the benefits of an STP cabling system, I don't believe it's necessary for all outdoor cameras.  STP components are far more costly, and more labor intensive to install.  It's not just the cable, but the patch panels, jacks, and patch cords as well.  This will add additional expense when compared to a properly designed UTP installation.

IP data is IP data.  Video requires reliable and timely delivery.  On the network we can apply QoS settings and other advanced networking features to ensure timely delivery of multiple traffic types, but if the packets don't transport reliability across the infrastructure it's a moot point at best.

Undisclosed Manufacturer #4

In reply to Undisclosed Manufacturer #1 | 12/21/17 08:34pm

It's not just the cable, but the patch panels, jacks, and patch cords as well. This will add additional expense when compared to a properly designed UTP installation.

 

Exactly, all of that is important because the cable must be properly grounded or the shielding can work as an antenna - improper grounding of STP can cause worse conditions than just running the cheaper, easier UTP.

Undisclosed #3

IPVMU Certified | In reply to Undisclosed Manufacturer #4 | 12/21/17 11:17pm

...the cable must be properly grounded or the shielding can work as an antenna - improper grounding of STP can cause worse conditions...

But just on the switch side of the cable, right?

Undisclosed Manufacturer #4

In reply to Undisclosed #3 | 12/27/17 10:20pm

Yes, as I understand it (and I am no cable expert) grounding at the switch, or patch panel side is all that is required.  Grounding both sides can cause ground loops but these tend to be on power-cycle frequencies which don't interfere much with Ethernet communications.  Having said that it is better to avoid ground loops altogether so why go through the extra work of grounding the jack end?

Avatar

Brian Rhodes

IPVMU Certified | In reply to Undisclosed Manufacturer #4 | 12/29/17 04:35pm

Grounding is done on one end only, although the specific end "field device vs switch" often varies according to manufacturer.

For example, many (access) reader manufacturers specify grounding at the reader, not the controller, or switch.  Some camera manufacturers, especially PTZs, include ground taps in the enclosure.

In general, the ground is more reliable if done at the switch rack, via TSB or some other central maintained earth ground.

As an FYI, we are prepping a test that looks at STP vs UTP shield effectiveness.  We will subject UTP and STP connected cameras to some nasty EMI to see what differences can be seen.  Look for that next month!

Avatar

Brian Rhodes

IPVMU Certified | 12/20/17 04:54pm

Thanks for the comment.  We refer to those BICSI guidelines and recommendations in our BICSI For IP Video Surveillance Guide and IP Networking course, and the 'best practices' aspect is useful. 

Installers should buy or find a copy of the TDMM even if the local AHJ has no idea what it is.

Undisclosed #3

IPVMU Certified | In reply to Brian Rhodes | 12/21/17 08:24am

 Installers should buy or find a copy of the TDMM...

Just don’t take Ethan’s copy:

 

Undisclosed Manufacturer #1

12/20/17 05:00pm

Thanks Brian.  I've been a BICSI RCDD for over 15 years... great training... great organization.  Agreed... every installer should have a copy of the TDMM as a reference manual if nothing else.  Merry Christmas!

Avatar

Brian Rhodes

IPVMU Certified | In reply to Undisclosed Manufacturer #1 | 12/20/17 05:03pm

RCDD = "really cool data dude"

Undisclosed Manufacturer #2

12/21/17 07:44am

Basic BICI knowledge will tell you that most signal current is carried by the outer surface of each copper conductor.  Not down the center so it makes it difficult to keep it from being interfered with.  Biggest give away is running cable in parallele with other type of cable.  Including inside conduit.

Undisclosed Manufacturer #2

12/21/17 07:52am

Problem we have is on large jobs the electrical contractor runs their own low voltage then hire a security integrator to finish the hand and bang portion.  In some cases the low voltage guy is only making 12% profit.  So if their is a mistake he can eat it big time.  So they will go the less expensive route.  Less expensive in Labor time and call backs.

I have seen security contractors use the local big cable house to run all the low voltage infrastructure then they can price their portion cheaper than the contractor/integrator that has all the work done in-house.

Dennis Ruban

12/24/17 06:24am

Back home in Europe we always called cable by type, like utp or ftp, etc. By default, it means you talking about cat 5e cable. If you need cat6, 6a, 7 for some reason, you just specify category as well.

when I moved to Canada, I figured, that most of the installers never heard about data cable types (utp is the only one) and they believe that cat5e is a cable for 100mbps and cat6 is for gigabit

Undisclosed #3

IPVMU Certified | 12/24/17 08:40am

 Other Names For STP

Yes, one may be best off using the full specifier instead of ‘STP’ considering the many different uses:

Undisclosed Integrator #5

12/28/17 04:40pm

There is an recomendation about analog cameras?

If I'm using a TP cable with baluns, have I use an STP cable to outdoor cameras?

Avatar

Brian Rhodes

IPVMU Certified | In reply to Undisclosed Integrator #5 | 12/28/17 04:54pm

Welcome, thanks for the question.

Because 'shielding' protects digital signals (EMI) differently than analog (signal loss), the importance is not for video quality as much as it is for cable run length.

As a point of illustration, coax cable is shielded by design, and the effectiveness of the shield corresponds to signal loss.  Thicker/more dense shielding (ie: RG6) versus thinner (ie: RG59) results in less loss over the length of cable runs.

In the case of twisted-pair/baluns like you describe, shielding would reduce signal loss, although the fact the wire is twisted to begin with also helps. 

Undisclosed #3

IPVMU Certified | In reply to Brian Rhodes | 12/28/17 05:14pm

Because 'shielding' protects digital signals (EMI) differently than analog (signal loss), the importance is not for video quality as much as it is for cable run length.

At least from a theoretical perspective, I would think the opposite, as far as video quality is concerned.

With analog, any noise that makes its way into the cable, and is not filtered out by common-mode-rejection will be present in the picture as artifact.

With digital, even the noise that makes it past CMR will usually be corrected/discarded by the reciever as it turns varying voltage levels into 1’s and 0’s.  It’s only the extreme noise that manifests in a digital signal.

IMHO.

*Edit: To clarify, I’m saying that the effect of STP on the analog signal quality is as important as that of run length.  Not that STP doesnt improve digital quality as well.

 

Avatar

Brian Rhodes

IPVMU Certified | In reply to Undisclosed #3 | 12/28/17 06:20pm

I am saying that an aspect of analog transmission - signal loss - comes into play sooner and is more important to address first rather than video quality.

Signal is lost no matter the external video quality EMI impacts.  Shielding helps mitgate this loss.

 

Undisclosed Manufacturer #1

12/28/17 05:17pm

Shielding helps prevent EMI (electrical magnetic interference).  Signal loss is caused by attenuation (loss as the signal strength travels the length of the transmission cable).  When it comes to coax or STP cable, both of these properties come into play.

STP cable will by default provide greater EMI protection over UTP cable, regardless of where installed (indoors or outdoors).  Cable twist reduces pair-to-pair cross-talk, which is signal jumping between the pairs within the cable jacket.  Attenuation can be reduced by using a thicker gauge wire.  Example, 24 gauge wire will have less attenuation that 26 gauge wire because of it's electrical properties.  With high end UTP cable, some products use 24 ga and some use 26 ga.  This is generally found in Category 6 rated cable and higher only.

Coax is a great medium for analog signals because of its robust shield and the physical size of it's conductor.  The challenge always was the cost of the material, cable path fill, bend radius, and home run design requirements.  UTP with baluns can help solve many of these short comings, and provide a future infrastructure upgrade path to IP camera connectivity.

I'm not disagreeing with Brian, just diving deeper into the weeds.

Chad Rohde

In reply to Undisclosed Manufacturer #1 | 12/28/17 10:42pm

UTP with baluns can help solve many of these short comings, and provide a future infrastructure upgrade path to IP camera connectivity.

 

I read somewhere years ago that UTP is recommended over STP when using baluns. I don't remember if it was a creditable source or the reasoning behind it. We have done it both ways without a problem in the past. 

Undisclosed Manufacturer #1

In reply to Chad Rohde | 12/28/17 10:52pm

Shields need to be grounded.  If the shields are not grounded properly, they effectively become antennas for EMI with no where to go.  This might be the idea behind the recommendation you cite.  Just a guess.

Chad Rohde

In reply to Undisclosed Manufacturer #1 | 12/28/17 11:14pm

It was something to that nature. But more along the lines of causing some type of self interference, not from an outside source. 

Either way, the few times we used STP and baluns, the shield never got grounded. 

Chad Rohde

12/28/17 11:00pm

Before I knew anything about codes, best practices, and what shielded or unshielded cable even meant, I worked for a company doing a lot of old work wiring. We would run wire breaking every rule in the book, twice, on the same 500' run. Looking back at it, it is surprising that we never really had problems other than the horrible connections we crimped using some primitive tools provided to us. 

And even now the only major problem I can think of concerning interference is the little AC/DC transformer wall worts. 

John you should start a pole to find out where others have found specific examples. I'm not much of a book person. 

Chad Rohde

12/28/17 11:30pm

Axis reasoning for STP outdoors is more than likely trying to protect their equipment. Not so much preventing interference.  Netonix provides some good hands on advise with outdoor cabling in this respect. It's specific to communication towers, but still relevant for outdoor camera runs. And backed by actual field experience.

 

Surges from Static, ESD, or ground potential shifts will take the shortest less resistive path like your Ethernet cable unless you provide a dedicated ground path that is of less resistance and shorter run to ground than your Ethernet cable - THINK SERVICE LOOPS

Undisclosed End User #6

03/04/21 07:46pm

I clicked on the conduit link and was surprisingly informed.

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