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Buddy Posted on 15/3 8:39
DAB frequency question

Any fule kno that Five Live broadcasts on 693 and 909 Khz, and Radio 2 on 88-91 Mhz. But you never hear frequencies referred to in the case of DAB broadcasts.

Anyone know what band they broadcast in? And what I would hear if I tuned a non-digital radio to them?

johns_ar Posted on 15/3 8:40
re: DAB frequency question

They dont give out the dab frequency because your dab radio just automatically finds it like a freeview box would.

Dont think you could tune a non digital radio into the right frequency to be honest.

Buddy Posted on 15/3 8:43
re: DAB frequency question

I know I don't NEED to know, but I don't need to know how an internal combustion engine works - I just like to know stuff.

I could if I had a non-digital radio with the correct frequency range.

--- Post edited by Buddy on 15/3 8:43 ---

borowally Posted on 15/3 9:54
re: DAB frequency question

Info

Link: DAB

BoroMutt Posted on 15/3 10:06
re: DAB frequency question

"I could if I had a non-digital radio with the correct frequency range" - no you couldn't the signal is broadcast as a digital stream of 1s and 0s and you need a DAC (Digital to Analogue Converter) to get an analogue output to amplify as speech/music.

AtomicLoonybin Posted on 15/3 10:11
re: DAB frequency question

Wikipedia says:

'DAB and FM/AM compared
Traditionally radio programmes were broadcast on different frequencies via FM and AM, and the radio had to be tuned into each frequency. This used up a comparatively large amount of spectrum for a relatively small number of stations, limiting listening choice. DAB is a digital radio broadcasting system that through the application of multiplexing and compression combines multiple audio streams onto a single broadcast frequency called a DAB ensemble. Within an overall target bit rate for the DAB ensemble, individual stations can be allocated different bit rates. The number of channels within a DAB ensemble can be increased by lowering average bit rates, but at the expense of the quality of streams. Error correction under the DAB standard makes the signal more robust but reduces the total bit rate available for streams. hgh


[edit] Use of frequency spectrum and transmitter sites
DAB gives substantially higher spectral efficiency, measured in programmes per MHz and per transmitter site, than analogue communication. However, since there are no plans yet to cease analogue FM transmissions, and most radio channels are transmitted both over FM and digitally, this advantage is not exploited to a high degree.

Numerical example: FM requires 0.3 MHz per programme. The frequency re-use factor is approximately 15, meaning that only one out of 15 transmitters can use the same channel frequency without problems with co-channel interference. This results in 1 / 15 / (0.3 MHz) = 0.22 programmes/transmitter site and MHz. DAB with 192kbps codec requires 1.536 MHz * 192kbps / 1136 kbps = 0.26 MHz per channel. The frequency re-use factor for local programmes and multi-frequency broadcasting networks (MFS) is typically 4, resulting in 1 / 4 / (0.26 MHz) = 0.96 programmes per transmitter site and MHz. This is 4.3 times as efficient. For single frequency networks (SFN), for example of national programmes, the channel re-use factor is 1, resulting in 1/1/0.25 MHz = 3.85. 3.85. 17.3 times as efficient as FM.

Note the above capacity improvement may not always be achieved at the L-band frequencies, since these are more sensitive to obstacles than the FM band frequencies, and may cause shadow fading for hilly terrain and for indoor communication. The number of transmitter sites or the transmission power required for full coverage of a country may be rather high at these frequencies, to avoid that the system becomes noise limited rather than limited by co-channel interference.'

No, me neither.

Buddy Posted on 15/3 10:12
re: DAB frequency question

Only the fourth line for me I'm afraid ALB.

Buddy Posted on 15/3 10:20
re: DAB frequency question

Mutt - are you saying that it simply isn't broadcast on traditional frequencies at all?

I understand that it's 1s and 0s that are received by the device instead of....errrr.....whatever normal radio signals are made of, and therefore you have to have a 1 and 0 decipherer to hear it.

But surely that signal has to be carried through the air in a wave form at a certain wavelength?

Capybara Posted on 15/3 10:27
re: DAB frequency question

Correct. You could technically 'tune in' to the signal but your radio would not make any sense of what was on the carrier. My guess is you would hear either white noise or nothing.

BoroMutt Posted on 15/3 10:32
re: DAB frequency question

Yes it is broadcast as a standard radio signal on the frequencies quoted in the Wiki article. And you can receive it with a suitable radio tuned to an appropriate settting - it's outside the standard FM radio range though. If you simply amplified this signal what you would hear would be like the noise when a modem or fax machine connects - high pitched warbling whistling noise. The DAC converts this to an analogue signal which can then be then amplified for the delectation of yerr lugs.

Interested to read that DAB+ is coming, thus rendering the old receivers obsolete. Basttaads.

Buddy Posted on 15/3 10:38
re: DAB frequency question

Aha.

"Eureka 147 DAB uses a wide-bandwidth broadcast technology and typically spectra have been allocated for it in Band III (174240 MHz) and L band (14521492 MHz), although the scheme allows for operation almost anywhere above 30 MHz. The US military has reserved L-Band in the USA only, blocking its use for other purposes in America, and the United States has reached an agreement with Canada that the latter will restrict L-Band DAB to terrestrial broadcast to avoid interference."

Both my original questions answered. I may experiment on my hypothetical receiver (which obviously I don't possess) capable of receiving 174-240 MHz later on.

Link: Wiki

Piquet2 Posted on 15/3 10:40
re: DAB frequency question

It's not carried on any 1 frequency, it is carried on blocks of frequencies called multiplex, you will also need a DAB aerial a dipole that is vertically polarised, similar to what is used for airband.

Buddy Posted on 15/3 10:43
re: DAB frequency question

My hypothetical non-existent device has a metal thing that is vertically extendable, if that's any assistance?

Actually it's technically diagonal because there are some hypothetical little feet at the front of the invisible machine to help you see the screen.

Piquet2 Posted on 15/3 10:54
re: DAB frequency question

It wouldn't not be called a pro2042 would it not?

Buddy Posted on 15/3 10:56
re: DAB frequency question

Can't remember. I didn't get it from Tandy about 10 years ago.

Piquet2 Posted on 15/3 10:58
re: DAB frequency question

I didn't get mine from Tandy about 10 years ago either.

Buddy Posted on 15/3 10:59
re: DAB frequency question

Just done an image search. I think if I ever did have such a device it would be one of them.

The_Frozen_North Posted on 15/3 11:18
re: DAB frequency question

All the stations contained in a DAB signal are broadcast simultaneously within the same signal. Each signal is digitally encoded when you 'tune' to a station you're simply instructing the radio to decode the specific station from the overall signal. The DAB radio probably has more processing power than the average PC had 10 years ago.

TheYak87 Posted on 15/3 11:49
re: DAB frequency question

this thread should mention 'lots of 1s and 0s' less and 'binary' more.