How long does it take for radio to reach me?

16 December 2012

Part of the show Extra Questions - The Science Behind Broadcasting

Fisher 500 Radio

Credit:

Question

After a day of boredom, I worked out that it would theoretically take 0.002 seconds for your show to reach me in Dundee (ignoring the time for your voice to reach the microphone and the time for the sound wave to reach my ears were ignored). However, I was wondering how long it would realistically take if electrical processes such as modulation, demodulation were to be taken into consideration (as well as other factors such as possible non-straight propogation) etc.
Love the show, it's certainly better than revision. Ross (Zoology student, Dundee University).

Answer

John - It does depend a lot on the transmission chain that's involved. It depends whether the radio station itself is digital, has a digital sound desk, digital processing amplifiers, and digital transmission lines to the transmitter site. All of these things can add a bit in terms of delay.

Typically, I would say that you'll be talking about less than 50 milliseconds in total for your average radio station. Maybe less than that if you have a completely analogue radio station feeding digital circuits.

If it's an analogue radio station, feeding analogue lines to the transmitter, which of course is analogue, with an analogue audio processor, the delay is virtually zero.