Where is the delay?

While watching one of the Pres/VP debates on TV, I also listened to it on FM radio. There was a distinct delay to the audio. To my surprise, the radio signal came earlier by almost a second.

As a kid, I could sometimes hear two network stations simultaneously when there was a distinct delay between the two stations that was much greater than could be attributed to radio propagation. I now attribute that to inductive telephone loading that greatly slowed down cable propagation speed.

As for present day practice, I do not know where the delay comes from. Some could come from satellite delays, but I do not think that it would be as big a delay as I observed. Fiber optic propagation would also be slower than the speed of light in vacuum. There can be computers that process signals that throw in delays. say by forming FFT and its inverse.

I would appreciate a minitutorial on where delays arise these days.


Reply to
Repeating Rifle
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"Repeating Rifle" wrote

Delays of live events are common so that scenes and sounds can be 'bleeped' as necessary. CBS could have bleeped out the 'costume malfunction' if they had cared to.

It used to be done with a tape loop. I am sure it is solid state now.

I don't know that they would have a bleep delay for a VP debate though, and the delay is usually in the 5-10 second range.

A one second slowdown on the TV signal makes sense, though: The broadcast came from Cleveland, so I am sure the signals all had to go to one of the coasts via satellite for production and then back by satellite to local stations for broadcast. There were lots of frame buffers the signal had to pass through on the way.

An alternative is the radio was running a 10 second bleep delay and the TV was running an 11 second delay.

Reply to
Nicholas O. Lindan

\ That order of delay (a fraction of a second) is almost certainly caused by one or two "hops" to a communications sattelite.

Delays of a SMALL fraction of a second are used to syncronize the network feed with the local TV station. A TV station might have a "black box" that stores a few frames of the network signal (each frame = 1/30 second) so that the station can switch among the network feeds, local feeds. special news feeds, and taped programming and maintain a proper video signal.

Delays measured in "seconds" are usually to permit producers to "dump" offending content. After the Super Bowl fiasco, you may see more of this in "live" sporting and entertainment events. But when you are broadcasting the debate between two people who each have a 50/50 chance of being POTUS next year, you don't have to worry much about the FCC.

Reply to
John Gilmer

there are 3 delay issues to be considered.

1: propagation delay. each leg of a satellite hop is about 23,000 miles. 2 legs per hop. usually 2 hops to the end user. 2: digital encoding / decoding while this is small it is not zero... usually a few mS per conversion. often the broadcast staion has a A/D D/A conversion as part of its studio to tramsmitter link. as far as i know all US sat feeds to radio are digital now. 3: profanity delays. despite the recient surge of delay buying, the great majority of radio stations do not have or will not use profanity delays for the following reasons: they're still expensive. $2 to 3 thousand depending on length of delay and if mono or stereo. it is impossible to monitor your own air signal. you have to listen in "program" rather then "air mon" when you talk. this makes it quite hard to mix properly and there is the possibility that the transmitter will fail and you wont know it happened until some listener calls to complain. its another thing to "gunk up" your audio.

most music radio stations "tape" edit and playback callers. they would not dream of putting a live caller on the air unless it was an extraordinary circumstance.

the real time talk shows are the ones that need the delay.

now we come to a satellite feed "special" like a presidential debate. what happens is someone activates the feed at the local radio station and then leaves. maybe this op comes back at the top of the hour to run a "legal ID" (or maybe he or she forgets) maybe the automation is sufficiently "smart" to run the ID (usually it is disabled for a special). so whether a delay is on or not is irrelevant as there is no one there to push the button anyway. if the special was a formatted event like a sports game where regular breaks are scheduled for local commercials there is a better chance of a live operator being on duty at the local level. even so many of these send "tones" that can automatically activate local ID or commercials.

as you can see there are so many variables that without knowing the exact equipment setup of each facility in question your question cannot be answered except in general terms.


Reply to

Super wonderful digital television introduces a quite noticeable delay. So much so that if you have a digital television and the person in the next appartment has an analogue television, then you could hear them cheer when a goal/point/whatever is scored, before you see it happen.

Sylvia (who thinks digital television is rubbish - at least as implemented in Australia).

Reply to
Sylvia Else

And pixelation. And compression artifacts.

Amen. And how about the big screen projection HDTV sets? $3000 and they don't distort the picture 'too bad', don't look 'too bad', and there's essentially no HDTV programming. At least around here. But there's still plenty of 'em selling here. I don't get it. Give me a 36" tube over a 54" rear projection, any day.

Otherwise, I have no point to make.

Thank you.

Reply to
operator jay

Yes - they're incredibly annoying.

I've wondered about those large screens for HDTV. Seems to me you need a living room with two sets of chairs. One distant set for watching the normal definition programs (so as not to see the lines), and one close set for the HD stuff. But then, what do I know? I'm still using an analogue set, cunningly supplied with an adequate roof antenna.


Reply to
Sylvia Else

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