TalkSport avaiable on FM wavelength? (two-part question)

[SurreyGuy]

Part 1

It was mentioned on one of the programmes the iother day that some guy abroad was listening to TalkSport on FM. I thought it was only available on medium wave?

Part 2

I always thought that FM was better than medium wave(with regards to quality of sound for the listener), so why doesn't everyone broadcast on FM?

T.I.A.

[Buenchico]

(Multi-part post):

I'll tackle the second bit first:

The radio signal broadcast by a transmitter consists of 2 parts. The first part is the 'pure' radio signal, which is transmitted on a certain frequency and contains nothing more than electromagnetic energy. The second part is the audio signal, containing the speech or music being broadcast. This has to be added on to the 'pure' signal by a process known as modulation.

There are two types of modulation used for broadcasting purposes. With amplitude modulation (AM), the 'pure' signal remains on the same frequency but its strength (amplitude) is increased or decreased slightly to represent the audio information which is 'placed on top of it'. The advantage of amplitude modulation is that, because the 'pure' signal stays on the same frequency, each station only occupies a very small part of the radio spectrum. The disadvantage is that, because the system uses minor changes in signal strength to encode audio information, the quality of the broadcasts is easily degraded by external factors (such as radio signals bouncing off the ionosphere).

The alternative system is frequency modulation (FM). With this system, the strength of the pure signal remains constant. However, the audio information is added on by slightly changing the frequency, above or below the nominal frequency, to represent the audio signal. The advantage of frequency modulation is that, because the audio information isn't affected by signal strength, the quality is much higher. The disadvantage is that, because the transmitted frequency has to go slightly up or down, the signals occupy more space in the radio spectrum.

[Buenchico]

Because radio waves don't stop at national borders, there have to be international agreements as to which parts of the radio spectrum can be used for broadcast purposes. If we ignore DAB for the moment, there are four such sectors available under these agreements. Three of these are 'long wave', 'medium wave', 'short wave'. The final sector should logically be called 'very short wave' but is actually referred to as 'very high frequency (VHF)'.

It would be technically possible for broadcasters to use FM signals on long wave, medium wave and short wave. The problem is that, as explained above, FM signals require a much wider part of the radio spectrum than AM signals. If radio stations used FM on, say, medium wave, you'd only be able to fit a handful of stations in across the whole width
of the dial. Remembering that the international agreements mean that there has to be sufficient space for stations operating in neighbouring countries, as well as in our own, this just isn't practical.

That just leaves VHF where FM can be used. When that part of the radio spectrum was allocated for broadcast use, it was only extremely narrow. That wasn't a problem at the time because it only had to accommodate three stations, i.e. the Light Programme (which became Radio 2), the Third Programme (which became Radio 3) and the Home Service (now Radio 4). There was no space for any other stations so, when Radio 1 started in 1967, it had to transmit on medium wave only.

[Buenchico]

The UK government eventually agreed to move the emergency services off the 95-108Mhz section of the dial, to free up some space (and to bring the UK into line with the rest of Europe). These frequencies were quickly filled by Radio 1 and commercial broadcasters. There is now no more space left. (It's this lack of space which is one of the driving forces behind the move to digital radio).

So TalkSport can't use FM on medium wave because their signal would be 'too wide' on the dial and interfere with other stations. (Even if they did use FM on medium wave, there are no radios equipped to receive it). And they can't use FM on VHF because there is no spare space on the dial for their station.

As far as the guy who said he was listening to TalkSport on FM, I have to say that I doubt the veracity of his statement. VHF-FM signals only travel short distances. Unless you happen to be around Calais, during a period of high pressure, it's very hard to receive any such signals in continental Europe. It's even harder, though, when they definitely don't exist!
http://www2.talksport.net/listen/listentous.as p?a=6&listen_id=99983
The only possible exception, that I can think of, is if a British military base overseas took a cable feed from TalkSport, they could broadcast it, via their own low-power VHF-FM transmitter, to people on (and around) the base.

Chris

[SurreyGuy]

Chris - superb post. Thank you very much.

[Buzz!!]

I'm willing to bet that the guy who was listening to talkSPORT on fm was in east central scotland.

Talk 107 and talksport are owned by the same company, and talk107 broadcast the George Galloway show.

[SurreyGuy]

Aha! :o)