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WCVB Engineering Maintenance

channel99

channel99

On 5-1 and 5-2 (MeTV) on-air and also on Comcast, WCVB is running an intermittent crawl that they will be off the air for an hour at 1:30 AM. They have a PSIP problem, currently - 5-1 is displaying as 20-3, and 5-2 as 20-4, and there is no EPG.
 
At 1:35, at the end of an infomercial on WCVB, they immediately shut down the transmitter with no additional notice. On Comcast the last video frame is frozen on the SD channel, and the HD channel and MeTV are blank.
 
The description you're giving suggests there's no PSIP at all. That's the system that's responsible for the EPG, and also for channel remapping.

Many TVs, if there is no remapping information available, they will use the station's physical channel number (20, in WCVB's case) and MPEG program number to assemble a kind of "fake virtual channel". It is very common (though by no means universal) for stations to use 3 for the MPEG program number on their first program & go up from there.

Judging from all that, I would suspect WCVB's work is not related to the transmitter itself, but rather to multiplexing gear or the studio-transmitter link. Or something more fundamental, like the AC power wiring or physically moving equipment.
 
It certainly appeared they shut down the transmitter, which is not at the studio site, but that might be done because there was no program feed. And they killed the direct feed to Comcast. It seemed to be very much last-minute, particularly in that they "pulled the plug" with no announcement, other than the crawls they had run earlier. Most planned maintenance tends to be early morning Mondays, not Saturday, so this may have been to repair something that failed, though if it was only the PSIP generator, that could have waited a couple of days I would I would think.

They were off more than a half hour, when I gave up watching, but checking again at around 5:30 AM - everything was back to normal, including the PSIP.

RabbitEars.info does show WCVB's "real" defaults as 20-3 and 20-4.
 
channel99 said:
It certainly appeared they shut down the transmitter, which is not at the studio site, but that might be done because there was no program feed. And they killed the direct feed to Comcast. It seemed to be very much last-minute, particularly in that they "pulled the plug" with no announcement, other than the crawls they had run earlier. Most planned maintenance tends to be early morning Mondays, not Saturday, so this may have been to repair something that failed, though if it was only the PSIP generator, that could have waited a couple of days I would I would think.

They were off more than a half hour, when I gave up watching, but checking again at around 5:30 AM - everything was back to normal, including the PSIP.

RabbitEars.info does show WCVB's "real" defaults as 20-3 and 20-4.
Click to expand...

Hmmm. I might think they had electrical work to do at the transmitter -- but that wouldn't explain shutting down the direct feed to Comcast. (which I would presume comes from the studio -- maybe not?)

PSIP generators generally "side-feed" the multiplexer -- and at least with our Thales gear, the PSIP data is cached in the multiplexer. At least in our installation, if the PSIP generator were to disappear altogether, the only thing the audience would notice is a gradual reduction in the amount of EPG data available. (as no new EPG stuff would be fed, and the oldest existing EPG data would disappear as it ages) In fact, our PSIP generator (a PC) has crashed without triggering *any* viewer complaints.

How sure are you the transmitted carrier was off? (did a "signal meter" show zero signal?) I'm wondering if maybe the transmitter was on, but just transmitting "dead air"? It's hard to tell with DTV, since you don't get "snow" on a channel with no signal.. Those crawls are generally written by non-technical people who may not have understood the difference between "off the air" and "transmitting dead air" -- and for that matter, is there a way to explain that difference to the audience without confusing them? :)
 
WCVB's transmitter is one of 4 that share the ill-fated top master antenna on the nearby CBS Tower, which had to be removed, rebuilt, and re-installed last summer. They were able to keep the Comcast feed active throughout those various outages.

Both a Zenith DTV box on one set, and a direct-connected Samsung TV, showed no signal, but that may, as you suggest, only indicate lack of a valid DTV signal. I have a Sencore level meter, but was just not motivated at that hour to check <g>.

I also don't know how long the PSIP data had been missing. My first thought when I saw the crawl was that there was a new problem with the master antenna, and decided to check WBZ, etc., and when I hit the down channel button from what should be 5.1, landed next on 12.2 (WPRI), which is why I noticed WCVB was displaying as 20-3.

They seemed eager to get to work, and must have been waiting for the end of the infomercial on 5.1 at 1:35 AM - since they pulled the plug during the disclaimer that follows those - somewhat humorously leaving that frame frozen on Comcast.

Perhaps there had been a bigger failure earlier, and the non-PSIP signal was the result of some temporary work-around. All just a guess, of course.
 
I've got a Zenith DTV box, and if it showed no signal, it meant it :) -- apparently the transmitter was indeed off.

I obviously don't know how WCVB is wired but I'm almost thinking they were doing two different kinds of work. Maybe they knew they were going to be doing some RF work & decided that was a good time to work on the PSIP too?
 
channel99 said:
WCVB's transmitter is one of 4 that share the ill-fated top master antenna on the nearby CBS Tower, which had to be removed, rebuilt, and re-installed last summer. They were able to keep the Comcast feed active throughout those various outages.

Both a Zenith DTV box on one set, and a direct-connected Samsung TV, showed no signal, but that may, as you suggest, only indicate lack of a valid DTV signal. I have a Sencore level meter, but was just not motivated at that hour to check <g>.

I also don't know how long the PSIP data had been missing. My first thought when I saw the crawl was that there was a new problem with the master antenna, and decided to check WBZ, etc., and when I hit the down channel button from what should be 5.1, landed next on 12.2 (WPRI), which is why I noticed WCVB was displaying as 20-3.

They seemed eager to get to work, and must have been waiting for the end of the infomercial on 5.1 at 1:35 AM - since they pulled the plug during the disclaimer that follows those - somewhat humorously leaving that frame frozen on Comcast.

Perhaps there had been a bigger failure earlier, and the non-PSIP signal was the result of some temporary work-around. All just a guess, of course.
Click to expand...

Here is the deal, and what can be the best guessed scenario in this situation. The PSIP generator is inline prior to the Comcast and the remaining ASI feeds going out. It is against the law for a station to transmit without PSIP, and whatever failed on WCVB's part, was in the transmission stream , which had to be broken to be troubleshoot/fix. (and before anyone gets their pants in a bunch, you have 10 days to get a technical transmission error fixed before notifying the commission, unless the error is causing intentional interference to other stations, i.e. you're over power). The transmitter was shut down, because most modern ATSC exciters, will mute the RF on the loss of input anyways. They have a Harris Sigma transmitter, so I am unsure of their configuration, but it makes the most sense that they killed the RF because it would've been killed anyways.

And yes, the "off time" is usually pretty hard, because the window to do work is short. 1:35 is 1:35, and if programming goes over, that is their problem, not ours (the engineers).
 
In these days of 24 hours programming, if a station goes down for quick maintenance do they have to show a standard sign-off/sign-on? And anyone know when the last time WCVB signed off other than related maintenance work?
 
channel99 said:
.....RabbitEars.info does show WCVB's "real" defaults as 20-3 and 20-4.
Click to expand...

I'm glad I saw this. I watch OTA on an analog set and a Zenith box, which for some reason "forgot" about Channel 5 over the weekend and skipped from 4.1 to 7.1. Entering 05.1 only brought up the "No Signal" screen. But when I punched in 20.3, voila. It brought up 5.1, switched quickly to the correct PSID, and hasn't acted wonky since.

(See? The "real" RF channels do matter. A little.)
(And yes, I know I probably could have just rescanned, but this saved time. Sort of.)
 
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