First and foremost for switched digital to work properly the set top needs to be interactive and needs to stay interactive.
Understanding how switched digital works is the next step. All set tops are assigned to a switched digital service group. When a customer tunes to a switched channel that channel becomes available to all set tops in the service group. When the customer switches off that channel a count down timer starts and when it reaches zero the channel is no longer available in the service group. This is where it gets tricky. The channel will stay available to the service group if another set top that is interactive is still tuned to the channel. If a set top is tuned to the channel that is not interactive it will go off once that timer runs down.(once the last interactive set top tnes off the channel)
The size of your service groups play a roll also. Overloaded service groups can run out of channel space if everyone is watching something different. Thats why switched should be used for those less watched channels. On the flip side house issues will stand out in sparsley populated service groups because they do not have the benefit of the someone already being tuned to the channel.
There are no meters I know of that specifically check the return path for a set top. Running a DOCSIS test on the outlet is your best bet. Its not perfect but its close enough, the return data carrier for set top is usually lower in the spectrum than DOCSIS returns are but considering a set top's Return Data carrier is usually a QPSK or an FSK its generally an even trade off.
Look at your non responding set top numbers, many set tops have not been interactive for a long time and the only way a customer would know is if they tried to use VOD. Have your System Techs run a Docsis test at the node and hook up a set top. Compare the Return data carrier to the Docsis return levels, is there enough headroom for the set tops? There may be some combining changes in the hub that can be made.
If this is your first time using set tops with cable cards you may have an issue with the cable card mac address not binding correctly.
Know what nodes are assigned to what service groups and let your staff know also. So as missing channel trouble calls start rolling in you can identify problems and head off truck rolls.
Widespread or area missing channel problems can be broken down into some main categories.
1. Usual plant issues: low signal, Mer / Ber off air ingress. System Techs should be able to resolve.
2. Overdriving of service group quams: Its not uncommon to see Switched quams sticking 4 or 5 db above standard quams. After a few amps in cascade distortions will wreak havoc.
3. Missing channel No quam: Something is wrong with the service group or the edge quam, escalate to the headend.
4. Missing Channel but has a quam (black screen): Usually need to escalate past the headend group to video engineering.
5. Missing channel has a quam but no Service group lock: You can identify this by tuning to the missing channels and going to the set top diagnostic screen. You should see the quams cycling through all your switched quams trying to get a lock.
Make sure your Service Tech's comment their escalations correctly. Channel name and number, quam frequency (if any), Black screen, Service group Lock, mer / ber. This will help tell the System Tech if he needs to go directly to the node and hook up a set top. Make available to your system techs how your switched quams are mapped in the service groups and what nodes are on what service groups.
Hope this helps. (please disregard any spelling errors :) )
Re: switch digital
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