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TV Sign ON/OFF Question.

R

RFGeek919

I have had a burning curiousity about the observance of my local TV stations, so forgive me if this question seems kinda cheesy and elementary. ;) A couple of years ago I remember watching the sign-off of TV stations, they would play the sign-off script followed by the national anthem... then the transmitter would shut off. Now, isntead of turning off the transmitter, they would simply display the channel number followed by the call letters and city of license until the programming would start the next day in the morning. Why do they do this? I would think it would save money and electricity to power them down. Unless it is hard on the transmission equipment to power them down each night, or maybe it has to do with keeping the signal on the cable side since some cable providers get their feed by air? Anyway, just a small question I have always wondered about. Thanks for your time :)

-- RFGeek
 
I'm not an engineer, but I'vr seen others on here state that yes, it indeed is hard on the transmitter to power it on and off each day. The other thing could be, what you are seeing is a feed from the station to the cable company (usually over data lines called t-1 lines, or some other kind of direct connection), and the OTA signal is actually off
 
Jeez, what town are you in? I didn't know any TV stations still sign off...but anyway, If you are watching off-air I have no idea...There would be a huge power savings shutting the transmitter down for a few hours every night...if you were watching cable the previous poster is probably correct.
 
I can answer why some stations leave on their transmitters...for the mere fact some of the older Analog transmitters may not come back on if turned off for more than 2 or 3 hours....more risk in blowing the damn thing up...no one wants to have to replace expensive tubes etc this late in the game...with Analog TV making an exit soon.

Bill H.
 
Not only is powering up hard on tubes, it is (in my experience) second only to lightning as the cause of shorts in the high voltage rectifier stacks which can take hours to repair if the boss is too cheap to have a couple of spares.

Also, it takes a while for a cold tube transmitter to settle in as far as maintaining the shape of the video envelope, although Tektronix developed the 1440 processor which eliminated the need for constant adjustment (front porch, sync, back porch, burst, blanking, video) which in the real old days required a transmitter operator to make constant adjustments all day every day.

The cost of power for 3 or 4 hours overnight is nothing in comparison to lost revenues if you can't get on the air for morning drive.
 
Thanks so much guys for answering my question. That makes sense to me now. I have seen TV transmitter tubes before and I believe it does cast ALOT of money to replace. The anologue to digital transition is not until 20010, from what I have heared. Thats not to far off. So I can understand that it WOULD be alot cheaper to leave it on rather than taking a chance on the loss of air time and wear on the transmitter itself. It is interesting to know about the transmitter operator that was needed in the young days of television. So much is invlovled in TV behind the scenes.
Just for your info, I never had cable at my home, it was always on-air stations. So, it was only a couple of years or so that I remember that the Des Moines market TV like ch.5 (ABC) 11 (PBS) would sign off. Now they stay on 24/7. I do alot of DXing also (TV and Radio), so when the stations would go off during the summer, I would see if I could get any distant stations. As a nerd, it was also fun to see the stations go off the air. Ch. 11 (PBS) would show the test patterns along with the time and slowly decrease power.. then shut off. *laughes* Anyway, thanks again for educating me. It is always nice to know theses things. I have to add one thing though, I will miss anologue transmissions, especially in radio. There is so much character in it, as far as DXing, pattern coverage, carrier, modulation, relfection, propagate, etc. Digital to me, seems so cold for some reason. Maybe I am just old fashioned. I hope it will be around for awile, including SW. I am getting off the subject, sorry about that ;) Thanks again!
-- RF Geek
 
I don't imagine they still sign off, but Mississippi ETV had the coolest "National Anthem" when they signed off in the 70's. It started with visuals of the revolution, and ran the gamut of American history through at least the moon landing. I remember KNOE, Monroe, used to sign off with the national anthem, followed by "Dixie".
RG
 
As an engineer, I can tell you that turning on and off every night is definately hard on the transmitter, and the savings of turning them off is miniscule compared to the increased costs of maintenance. Back in the mid-90's, I was working for an FM station that signed off from 11 p.m. and 5 a.m. It was a weekly struggle to keep the old Collins 830-10 KW transmitter running. Anyway, I finally talked the owners into commencing 24 hour-a-day operation. That old Collins ran so much better after that, and in fact, after being off the air at least once every 2 weeks before, I think it only went off 3 or 4 times in the 3 1/2 years after that until it was replaced.
 
what about daytime only AM's?, especially ones that are still on tube transmitters. at the AM I worked for, we would leave the filaments on all night but turn the plates off...

WTKR TV 3 in Norfolk VA still signs off...but runs a test pattern at night
 
I haven't seen a TV station sign off at night in many years, but the question that arises in my mind as far as the stations that still do but leave their TX on, is why not throw some programming at it as long as it's fired up? Automation isn't too hard to come by these days, and as long as the transmitter is up, why not broadcast something other than colorbars?

-A
 
Alan Fletcher said:
I haven't seen a TV station sign off at night in many years, but the question that arises in my mind as far as the stations that still do but leave their TX on, is why not throw some programming at it as long as it's fired up? Automation isn't too hard to come by these days, and as long as the transmitter is up, why not broadcast something other than colorbars?

-A
Click to expand...

They would probably have to pay the syndicator of each fill program something to run it.
 
Andy Brown said:
The cost of power for 3 or 4 hours overnight is nothing in comparison to lost revenues if you can't get on the air for morning drive.
Click to expand...

Since when does TV have a "morning drive"? That'd be a bit scary.
 
EncSpy said:
what about daytime only AM's?, especially ones that are still on tube transmitters. at the AM I worked for, we would leave the filaments on all night but turn the plates off...
Click to expand...

So far as the Daytime AM's go, they will still have to cut the carrier off at night, or risk an FCC fine. That is the whole purpose of having Daytime only AM. If they could leave the carrier on, they might as well go ahead and program it eh?

Almost every AM and FM that I worked for, always killed the carrier at night, but left the filaments on. It is the power surge to the filaments that is the biggest tube killer of all. Now if you were lucky enough to have a solid state transmitter, it would be whole different story.
 
Hey Spike,
I know quite a few others that sign off or at least used to sign off at night. In the twin cities, the PBS stations signed off at 12 and 1. In the Eau Claire, WI market, the ABC and the PBS stations both signed off at night.

Part of what killed KURE's old transmitter was the constant sign-on and sign-off. Glad that automation system is in place for the overnights (!!)
 
Yes...I was wondering the same question myself. Makes total sense knowing that the analog TX's will be useless in 3 years.

Our PBS stations where I used to live (Richmond, VA) used to physically sign off at midnight. Now, they run test pattern with the audio feed from the NPR affiliate.

But yes, stations actually do sign off at night...though most of them are now PBS stations. Makes me wonder, when the transition to digital is complete, will many of these stations run 24/7 programming?

Radio-X
 
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