h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

the other day while working in the house i had radio 2 on in different parts of the house on different equipment

Bedroom - FM Radio
Living room - freeview digital TV
Kitchen - DAB digital radio

and i noticed a delay between all 3 formats of upto a couple of seconds,

none of the equipment was in sync,

what i want to know is

when the "Pipps" time signal is broadcast which one is the accurate one
FM, DAB or Freeview????

Common sense dictates that it must be the first one.

B

As Mu says the FM one is accurate(ish). The digital signal for radio and TV is currently converted from the analogue source that is broadcast as FM hence the delay. If you try it with a fourth source, internet streaming you will get yet another delay.

turvy

Technically, none of them are accurate because the signal still can only travel at 3x10^8 m/s. But, I would say that the one that arrives to you first would be the most accurate.

Traveller in Time calculating
"If you place the FM receiver at sufficient distance you will hear the beeps at the same time as the digital receivers.

The exact time is of no importance in normal life, you only have to find out how long something lasts. "

FM is most accurate as it is subject to least encoding/decoding/transmission delay.

The only thing I can think of that required knowing the time to that accuracy was a performance by the Red Arrows. The commentator arrived by helicopter prior to the performance, and gave the usual intro spiel. He then pointed out that the team were scheduled to arrive at precisely 1 o'clock, and that he had a bet with the team leader whereby every second the team were late or early crossing the display field, they each owed the commentator a pound. Nine planes, a quid per SECOND for delay or early arrival, flying at a speed of over 400 miles per hour trying to arrive at a specific point the size of a couple of football pitches.

The PA was connected to BBC Radio 4 FM for the pips... and the commentator didn't get a penny. Unbelieveable.

Indeed. This raises another question. We've got a telly in the living room (Sky) and one in the kitchen (archaic analogue), and there is a noticeable delay between the two. This makes sense, since the Sky signal has to travel 36,000km up to the satellite and back.

But after reading this thread I did the sums and, everything else being equal, the Sky signal should be over four seconds behind. But it's nearer two seconds. Why?

Actually, scrub that, I got the sum wrong

Guessing you missed a decimal place? I recall satelite internet having a ping of 400 or so miliseconds. Don't try playing games on it unless turn-based.

This thread has a great title.

You guys have heard of "proper time", right?

http://en.wikipedia.org/wiki/Proper_time

I had to stand up to get that Arnie.

t.