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Press “space” to start !. Presents…. Page 0100 0100 Text-TV Your favourite Channel Monday 18. October 1999. Connecting and Return Path in CATV Networks. Page 0100 0100 Text-TV Your favourite Channel Monday 18. October 1999. You have probably seen this before.

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Page 01000100 Text-TV Your favourite ChannelMonday 18. October 1999

Connecting and

Return Path

in CATV Networks

slide4
Page 01000100 Text-TV Your favourite ChannelMonday 18. October 1999

You have probably seen this before...

slide5
Page 01000100 Text-TV Your favourite ChannelMonday 18. October 1999

Your favourite TV Channel

News.............. 110

Sport ............. 200

Latest ............ 130

Advertising ..... 700

TV today ........ 320

Cabelcon …..... 600

slide6
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Y((r favoüüt Tü Ch!!%nel

Ne++/6.....¤56...... 1ae

S#¤??rt ......?”.... /00

Lat”#st ............ 130

Adverti¤%&/s ... 7I)00

TV tod¤¤y ........ 32&

Ca!elc/n …..... %00

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Page 01000100 Text-TV Your favourite ChannelMonday 18. October 1999

Your favourite TV Channel

News.............. 110

Sport ............. 200

Latest ............ 130

Advertising .... 700

TV today ........ 320

Cabelcon …..... 600

- and you know

why too!

Right?

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Page 06050605 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Lacking system performance…!

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Page 06070607 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Safe signs of poor system performance with analogue TV signals:

Ghost pictures

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Page 06120612 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Safe signs of poor system performance with digital downstream signals...

Increased bit error rate.

Typical “visible” results of this will be...

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Page 06150615 Text-TV Cabelcon ConnectorsMonday 18. October 1999
  • TV-Text unreadable.
  • Noisy (or no) digital sound (NICAM).
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Page 06180618 Text-TV Cabelcon ConnectorsMonday 18. October 1999

- and at digital upstream signals?(using the return path band)

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Page 06200620 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Poor system performance in a CATV network could originate from…

  • Poor return loss values
  • Poor carrier to noise level
  • Insufficient screening followed by...
  • Ingress of noise and unwanted signals
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Page 06230623Text-TV Cabelcon ConnectorsMonday 18. October 1999

There can be many reasons for decreased performance.

  • Here we will concentrate on...
  • Poor or incorrect cable preparation and connector installation.
  • Unreliable connector quality.
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Page 06260626 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Most return path problems originate at the subscriber’s end of the network...

  • It’s a well-known fact, that 75-80 percent of service calls are related to drop installation.
  • -and that around half of those are caused by poor connections!
  • (Just one under-tightened connector can course serious trouble in your network!).
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Page 06290629 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Noise and unwanted

signals will be added from

all parts of the network.

Noise from just one singlesubscriber can block the return path system completely!

  • Intrusion of “Man-made” noiseoriginates from
  • Computers
  • Refrigerators
  • Heaters
  • Thermostats
  • TV-sets
  • Cellular phones
  • - and from lots of other sources!

Subscribers

Node/

head-end

Node/

head-end

Upstream blocked

Upstream

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Page 06310631 Text-TV Cabelcon ConnectorsMonday 18. October 1999

“No chain is stronger than the weakest link”

- and the weakest links in a CATV network?

Connections...

- and there are thousands of them!

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Page 06350635 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Let’s take a look at the most frequent connection problems...

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Page 06370637 Text-TV Cabelcon ConnectorsMonday 18. October 1999

This is an example of a screw-on connector and a cable which have been exposed to salty moisture for just 300 hours:

Metal in the cable is close to disappearing!

Heavy corrosion

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Page 06390639Text-TV Cabelcon ConnectorsMonday 18. October 1999
  • This will lead to..
  • Signal egress & ingress
  • Intermodulation distortion
  • Ghost pictures
  • Loss of return path data
  • Loss of forward signals
  • Blocking at the node
  • System downtime
  • Expensive repair costs
  • - and the results of corrosion:
  • Poor screening
  • Poor return loss
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Page 06420642 Text-TV Cabelcon Connectors Monday 18. October 1999

Let’s take a look at PIM - Passive Intermodulation

(CPID - Common Path Intermodulation Distortion)

  • Moisture creates a layer of oxide between two different layers of metal (like a sandwich: Metal- Oxide-Metal).
  • Oxidation creates a semiconductor effect (like rectifier diodes).
  • Diodes act naturally as frequency mixers and multipliers.
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Page 06450645 Text-TV Cabelcon ConnectorsMonday 18. October 1999

- and furthermore on PIM...

  • Carriers present in the network will be mixed and multiplied by the sum and difference.
  • All these “new” created and unwanted carriers (intermodulation) will appear at more or less unpredictable frequencies.
  • PIM will be more “visible” below the FM-radio band (return path range) due to lower cable attenuation!
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Page 06480648 Text-TV Cabelcon ConnectorsMonday 18. October 1999

PIM - Passive Intermodulation - schematic

Two connector parts (or cable/connector parts)

Mixing of carriers and frequency multiplication create many “new” carriers (PIM).

Occurrence of diode effect through oxidation

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Page 06520652 Text-TV Cabelcon ConnectorsMonday 18. October 1999

PIM, return loss and ingress problems grow at low frequencies (in return path band)...

  • Cable attenuation is low (negligible). Almost no attenuation of reflected carriers caused by poor return loss.
  • Frequency difference products (PIM) - caused by corrosion, are typically generated at low frequencies. Disturbance occurs in the return band.
  • Considerable decrease in cable screening attenuation below 30 MHz. Extensive risk for ingress of unwanted signals and noise. Radiation will increase with poor return loss.
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Page 06550655 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Poor return Loss...

Reflections andloss of wanted

signals

Increased radiation

Forward signal

Amplifierw/return path

Amplifier

Coaxial Cable

Reflected signals + upstream (return path)

Corroded or

badly installed

connection

Increased bit error rateand loss of data or

transmission speed!

What happens?

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Page 06570657 Text-TV Cabelcon ConnectorsMonday 18. October 1999

How can we prevent or minimise problems in the return path band?

  • First of all through...
  • Use of quality connectors
  • Use of the right type of connector for your application.
  • Use of quality cables with a high degree of screening.
  • Proper installation practices.

Let’s see some more examples...

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Page 06600660 Text-TV Cabelcon ConnectorsMonday 18. October 1999

The result after inspection...

- while the cable installed with ourmoisture proof typeremains unaffected!

Darkened copper foiland braid. A pre stageto corrosion - throughingress of moisture.

Poor return loss &PIM will sooner or lateroccur after a certain time with corrosion

- You can see the difference!

This is a standardcrimp connector for indoor use

- and this is a moisture proof type for outdoor use!

Two different types of crimp connectors - both manu-factured by Cabelcon - are mounted on a piece of cable.

Both have been exposed to salty moisture for 300 hours in a chamber.

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Page 06630663 Text-TV Cabelcon ConnectorsMonday 18. October 1999

- and the same result can be seen on an UltraSeal™compression connector

No moisture ingrees!

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Page 06650665 Text-TV Cabelcon ConnectorsMonday 18. October 1999

- this applies to connections at all levels...

- from the smallest drop connectors...

- to the bigger trunk connectors.

precise installation is important an example
Page 06750675 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Precise installation is important!

An example...

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Page 06760676 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Two cables - one prepared with a special tool, while the other one was stripped in the old fashion way, using a tube cutter.

Special preparation tool

Ordinary tube cutter

Visible difference: The outer conductor was 2 mm too short on the “hand stripped” cable

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Page 06770677 Text-TV Cabelcon ConnectorsMonday 18. October 1999

The result after installation and test...

Measured return loss was two dB worse on the “tube cutter” stripped cable/connector.

“Just two dB? ”

It could easily be more than two dB in each connector all the way from head-end to subscriber!

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Page 06780678 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Preparation tools

  • Preparation tools - especially designed for the combination ofyour cables and connectors - will ensure a precise installation and...
  • Prevent or minimise return path problems in your network.
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Page 06790679 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Finally some advise...

  • Do not use screw-on connectors for professional applications.
  • Choose the right type of connectors for your applications.
  • Use moisture proof types (or heathshrink tube) for outdoor installations.
  • Read and follow the manufacturers instructions for proper cable preparation and installation of your connectors.
  • Use appropriate preparation tools - when available - for your connectors/cables to ease installation and to ensure optimal performance of your network.
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Page 06800680 Text-TV Cabelcon ConnectorsMonday 18. October 1999

If you have any questions or require more information...

- please visit our stand no. 438

This presentation can be downloaded fromwww.cabelcon.dk/ecc99.htm

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Page 06850685 Text-TV Cabelcon ConnectorsMonday 18. October 1999

Thank you for watching

this presentation from

A Cabelcon production

Presented by Jeremy Stubbs

Copyright 1999 by Cabel-Con A/S

All Rights Reserved

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