Stations can't be sure that the transmitter will be able to turn on after shutdown, and leaving it on all the time is less stressful than turning it off each night. This is why almost all stations are on 24 hours a day, except for AM daytimers. When TV stations used to sign off at night, they usually showed a still image or something instead of turning off the signal. The amount of electricity used at night to transmit costs very little compared to the total costs of operating the station. In many areas, electricity is cheaper at night than in the day.
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Test tone on 1630
- Thread starter mofocat
- Start date
Definitely this. I was going to post the same thing, but thank you for doing so in a way that's even helped my understanding
WSMW-TV (later WUNI), Worcester MA, in the early analog days had a water cooled UHF transmitter. Because of the amount of heat generated by the transmitter, little or no additional heat was needed to heat the building. They did sign off for 4 hours or so nightly, though. Apparently one morning, per local legend - after a particularly cold night, the transmitter started up OK, however, after a few minutes, some section of the cooling system thawed out, having frozen during the night - and the water soon put them off the air, which required a few days to clean up. After that, they began running the transmitter all night in cold weather. Not, of course a problem in a warm climate.
A couple of quick tidbits.....
Back in the early 70s, an engineer at WEAU-TV in Eau Claire, WI (NBC ch 13) told me that the reason they ran movies or syndicated reruns after Johnny Carson signed off was to have as many TVs as possible tuned to channel 13 when they were turned on again the next day (the other two sations in the market, CBS and ABC signed off at midnight). I'm not sure to what extent they accomplished that, but the post-midnight programming was stuffed with bonus ads for local advertisers and pay-for-performance stuff from K-Tel, Ginsu knives, etc. So they must've recouped at least a small portion of their cost of staying on later than their competitors. Directly or indirectly.
Going back to radio stations leaving their transmitters on to broadcast a tone.... I recall WSM doing that every Monday morning after midnight. I don't know if they still do that.
Back in the early 70s, an engineer at WEAU-TV in Eau Claire, WI (NBC ch 13) told me that the reason they ran movies or syndicated reruns after Johnny Carson signed off was to have as many TVs as possible tuned to channel 13 when they were turned on again the next day (the other two sations in the market, CBS and ABC signed off at midnight). I'm not sure to what extent they accomplished that, but the post-midnight programming was stuffed with bonus ads for local advertisers and pay-for-performance stuff from K-Tel, Ginsu knives, etc. So they must've recouped at least a small portion of their cost of staying on later than their competitors. Directly or indirectly.
Going back to radio stations leaving their transmitters on to broadcast a tone.... I recall WSM doing that every Monday morning after midnight. I don't know if they still do that.
Apparently, KOMO-1000 also went off on Monday mornings but also left a 1khz tone on all night. This would have been in the 1970s. The reason being -- KOMO was the main emergency broadcast station for the Puget Sound area and needed to stay "on" with a tone in case they had to break in for an emergency situation.
That, and a single continuous sine tone requires much narrower audio deviation/bandwidth to transmit than regular programme audio, so it is easier to pick out of static or a mess. This is why signals like longwave and low-mediumwave NDBs can sometimes be observed hundreds of miles away from their source airports at night, even in the presence of things like DGPS or local harmonics.
If your receiver has adjustable sidebands as many SDRs these days have (e.g. Enschede) then it can be set to only a couple hertz bandwidth and the cursor placed on the carrier frequency with the window at the appropriate offset. E.g. 1630 kHz USB with a 3 Hertz CW window at +1 kHz above the carrier, brickwalling everything else around the tone.
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I had that happen over on KiwiSDR (one of the Fort Collins, CO ones) where a most of the lower part of the MW band had a het tone on it, and so I adjusted it to Lower Side Band (the tone was on the upper part), and it got rid of the tone.
That must have been a more 70's thing. In the early 60's, they left the air for maintenance at midnight, PST. In the eastern U.S., some of us were lucky enough to check 1000 in the next hour and were rewarded with 1ZD, Tauranga, New Zealand, a 10 kw local station. I heard it several times in that window just before the 4 AM EST sign on of Radio Record in Sao Paulo, Brazil
And, since one of the most stressful things for a transmitter is just turning it on, one does not want to have the gear fail just at the start of the most profitable part of the day.
6 AM failures caused me to go 24/7 with all of my stations and about a dozen transmitters as far back as the mid-60's.
Today, gear is so reliable that this is really not necessary, but it is so easy to run overnight with automation that most stations do not sign off. "Back in the day" when equipment had tubes that glowed red-hot, the heating and cooling was far more destructive than to just keep on the air permanently.
That's why they used to half-jokingly call CONELRAD the "transmitter stress test"! The repeating "off-on-off-on" cycling would sometimes wear out transmitter valves and cause them to fail prematurely.
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Not your decision. Chances are there's a reason which none of us will every be privy to.
I know that, It's just a opinion
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