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SPAC (System Performance Analysis for CATV Systems) is a tool for planning the performanceof CATV distribution networks and their return path channel.

SPAC calculates all important system parameters like Output power CNR (carrier to noise ratio) CSO (composite second order) CTB (composite triple beat) BER (bit error rate) MER (modulation error ratio)

The tool SPQA (Subjective Picture Quality Assessment simulates the influence of the parametersCNR and CSO/CTB to an analogue transmitted test picture.

The demo version SPAC_DEM.EXE allows calculating CNR, but not CSO, CTB, BER and MER.In addition, it is not possible to load, save and print networks.

SPAC uses modules of BKtel, which are grouped together in libraries. Predefined lists for differentchanne l allocations and services (PAL B/G, NTSC, Cenelec 42, ) are part of the delivery.

In the following you see an example of a SPAC calculation run.

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At first, install SPAC with unzipping the zipped file SpacDemo.zip to a new directory on your harddisc.

S tart SpacDemo.exe. At the first start of SPAC it opens automatically SPAC User Guide. Youmay close it now. It is possible to open it with Help or at any time.

Create a new network with File->New or click at . SPAC installs a signal source (Source) asfirst component of the network.

Activate a channel list with Channels->Read Channel List. Select cenelec.lst.

Add an optical transmitter with Add->OTX or . Select otxe090b.lis. This is the transmitterOTXE090B with integrated preamplifier (LCA = Load Controlled Amplifier). In SPAC, it is modeledas module list (double module: Amplifier plus transmitter).

Press Calculate for a first intermediate calculation. SPAC displays the output power Pout andthe carrier to noise ratio CNR.

A doubleclick on the OTXE090B opens the module list anddisplays the parameters of both components.

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An additional doubleclick on the moduleOTXE090B opens the detail view of theoptical transmitter.

Now close it with and closethe module list with a click on the darkgrey background.

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This is the result of the simulation. The calculation of CSO und CTB is suppressed in the demoversion.

To try out:

Open the second optical line (OptLoss #5) und change the splitter ration from 1:1 auf 1:2, 1:3 etc.Watch how the CNR gets worse.

You may also select other transmitters, other amplifiers and so on.

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To try out the tool SPQA (Subjective Picture

Quality Assessment), the selected channel listmust use modulated carriers.

To do this, open the channel list withChannels->Edit Channel Table and markmodulated carriers.

After the acceptance with start a newcalculation with Calculate!.

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The tool starts with SPQA! inthe SPAC menu bar.

It uses the CNR value 50.2 dB,which was calculated fromSPAC.

In full version SPAC takes overalso the CSO and CTB values.But in demo version, they arefixed to 65 dB.

CNR and CSO/CTB may be adjusted with Distortions.

Decreasing carrier to noise ratio (less CNR) leads to increasing noise distorted pictures.

Less distance of intermodulation distortions (less CSO/CTB) leads to moire effects.

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For calculating the digital parameters BER and MER, you have to select a digital service. To dothis, open menue Channels->Read Channel list and choose europe.lst. Select the servicewith Channels->Service->64 QAM and press Calculate!.

Please notice that the display of BER and MER is suppressed in demo version.

Standard version of SPAC is available for 1.995.- ,

contact per eMail to: sales-sys@bktel.com.