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#185156 - 03/04/09 06:05 PM Digital CATV signal tester  
KJay  Offline
Joined: Nov 2007
Posts: 763
I have a question regarding a CATV tester I have that looks for signal on channel 3 to verify an active line.
I'm wondering how likely it is that this tester will still continue to work as designed when the switch to digital TV actually takes place this June.
Will any of the traditional RF type CATV signal meters or analyzers in use now continue to function as intended after the change to digital takes place or must they be replaced?

If not, what type or brand of meter would you recommend for analyzing the new digital CATV and broadcast signals?


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#185173 - 03/05/09 12:19 AM Re: Digital CATV signal tester [Re: KJay]  
frenchelectrican  Offline
Joined: Feb 2003
Posts: 939
Wi/ Paris France { France for ...
I will get ahold of one person maybe he know some details I am not sure if he can give you some info so hang on tight he may reply soon.


Pas de problme,il marche n'est-ce pas?"(No problem, it works doesn't it?)

#185217 - 03/05/09 10:56 PM Re: Digital CATV signal tester [Re: frenchelectrican]  
JoeTestingEngr  Offline
Joined: Nov 2005
Posts: 791
Chicago, Il.
I would imagine that a cable company that has an analog NTSC signal on Channel 3 now, will have one there in 2 or 3 years. Their demod equipment will have to change if they are receiving an over the air ATSC digital signal. They would still use the same modulator though. That's why they said you didn't have to do anything by 2/17/09 if you have cable.

#185225 - 03/06/09 02:33 AM Re: Digital CATV signal tester [Re: JoeTestingEngr]  
JoeTestingEngr  Offline
Joined: Nov 2005
Posts: 791
Chicago, Il.
One thing that gets me about DTV, is that channel numbers mean absolutely nothing. In NTSC, Channel 2 means a 6 MHz bandwidth from 54-60 MHz. The visual carrier is at 55.25 MHz unless the station license has a plus or minus 10KHz visual carrier offset. In Chicago, Channel 2 is the only VHF station that has its DTV signal in the VHF band. My converter shows it to be in the band widfh of Ch.3 at 63MHz. Ch. 005-3 appears to be on a ch.29 at 563 MHz UHF and with no rhyme or reason to any numerical order.

Now having been a Maintenance Supervisor and Chief Engineer of 2 different full power UHF stations, I'm no slouch on TV of olde. But I freely admit to being totally clueless to this new stuff. A while ago, I posted on how I would love to see some spectrum analyzer displays. I also wonder about the output power of a station's DTV signal relative to licensed NTSC output. Our combined visual output in Cleveland was 110KW for a 2MW ERP. The 110KW is tip of sync and probably has no bearing on rating output power of a digital signal. I guess I just haven't been curious enough to look it up.

#185236 - 03/06/09 01:26 PM Re: Digital CATV signal tester [Re: JoeTestingEngr]  
brianl703  Offline
Joined: May 2005
Posts: 166
Manassas, VA
The channel numbers don't always mean anything for analog cable TV. Years ago the local cable company's channel numbers only meant something if you used the Scientific Atlanta converter they supplied. If you used a cable ready TV without a box none of the channel numbers were correct. Not a single one. They eventually started publishing a list of channels for cable-ready TVs and then finally did away with the "channel mapping" entirely, so that the channels on the converter and a cable-ready TV are the same.

#185239 - 03/06/09 02:12 PM Re: Digital CATV signal tester [Re: brianl703]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,136
This thread has moved away from the original question but I bet that "detector" is just looking for RF modulation on the frequency of good old channel 3 and doesn't care if it is NTSC, PAL or any of the implementations of digital.

Greg Fretwell

#185241 - 03/06/09 02:40 PM Re: Digital CATV signal tester [Re: gfretwell]  
KJay  Offline
Joined: Nov 2007
Posts: 763
Thanks for the replies.
It sounds like it will probably just end up being a non-event as far as signal analysis goes, so the prudent thing to do may be to simply wait and see what happens when the poop finally hits the fan before looking into any new test equipment.
Not the usual approach I like to take in these looming deadline situations, but given the wave of information vs. misinformation surrounding this event and now the added delay in implementing the DTV changeover, I am still generally very much in the dark as to what to expect with any of this anyway.

#185251 - 03/06/09 09:42 PM Re: Digital CATV signal tester [Re: KJay]  
noderaser  Offline
Joined: Mar 2007
Posts: 404
Portland, Oregon, United State...
The FCC deadline does not apply to cable, only broadcast television. Many cable companies are opting to make the transition voluntarily, as it decreases their bandwidth requirements to send the same content to its customers. It also means that everyone will get some form of "on demand" programming... Probably a gimmick to get you hooked on the free stuff, so you'll buy the "pay per view" stuff.

The company that serves our area, Comcast, has been doing a really good job about telling people that they're going to be ok with the transition if they're Comcast customers. What they don't tell everyone is that they will be switching to all-digital as well, so any existing cusotmers will need to get a new digital set-top box to continue watching cable. The poor communication about this transition has been a point of concern for the school district I work for, as we have a substantial contract with Comcast. Their solution was to give us 10 set-top boxes per school, when some schools have around 50 TVs... Not to mention that some of them also have in-house broadcasts that won't mix nicely with the external digital feed. We're still waiting on the reply from Comcast, but the general stance from the district is "give us somethig that will work with our TVs and in-house broadcasting, or loose us as a customer". It's likely that we will have to re-broadcast analog to the classrooms.

If your tester is just looking for any "signal" at that frequency, it will probably work; if it's looking for the carrier or another specific signal, it may not.

#185261 - 03/07/09 03:01 AM Re: Digital CATV signal tester [Re: noderaser]  
hbiss  Offline
Joined: Dec 2003
Posts: 886
Hawthorne, NY USA
I would agree that a simple tester that only looks for RF won't have any problems. Where you will have a problem is with the meters that do actual signal level measurements. They must be designed and calibrated for, in the case of CATV, QAM as well as analog and you need that now. For off-air it will be 8VSB. Some meters will handle both.

In a short while most CATV systems will be eliminating the analog channels simply because they are bandwidth hogs. They can put 10 digital channels or 2 HD channels in the 6 Mhz bandwidth of an analog channel.

This change has nothing to do with the over-the-air digital conversion now rescheduled for April.


Last edited by hbiss; 03/07/09 03:05 AM.

#185263 - 03/07/09 04:01 AM Re: Digital CATV signal tester [Re: hbiss]  
gfretwell  Offline

Joined: Jul 2004
Posts: 9,136
When the cable company makes me rent a box for 4 TVs a VCR, a DVR and a DVD recorder the satellite sure starts looking better. They start you put with 4 boxes, cheaper than cable for 1 and more channels.

Greg Fretwell

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