Sv: [HCDX]: Medium wave bandwidth + popularity

["Stig Hartvig Nielsen" <hartvig@xxxxxx>]

> I think you're confusing bandwidth, with bandpass and channel spacing.
> The channels are spaced every 9 kHz, and theoretically the station stays
> inside the + or - 4.5 kHz with its sidebands.

No I am not confusing bandwidth with channel spacing. Channel spacing is 10
kHz in the Americas and 9 kHz in the rest of the world.

Bandwidth is the "amount of space" on each side of the center of a
frequency you are allowed to use. And in Europe thats a mere 4.5 kHz which
gives a very poor telephone-like audio. In the US and elsewhere it's
different - they have more space and obviously - a programme where you also
can hear the tones from 5-10 kHz (and not only less than 5 kHz) sounds a
lot better.

I know that - if you are using poor 4.5 kHz filters quite a lot energy
would also be radiated at 10 kHz from the center frequency - but thats
another story and that wouldnt improve the audio quality.




> In AM the sidebands are directly proportional to the modulating
frequencies...
> pump in a 5 kHz signal and your side bands are + or - 5 kHz.
> However, the info carried in EACH of the sidebands is identical

Yes!  And when you pump in a 6, 7, 8 og 9 kHz tone that will be cut away in
the filter. In Europe !!


 

> Here in the States, I'm told stations can feed up to a 7500 hZ signal
into the
> modulator of a transmitter, so that the occupied bandwidth is 15 kHz, not
the
> 10 kHz that's allocated. No interference (except to DXers) results. And
even
> here, the sidebands being generated are greatly reduced in strength since
most
> audio intelligence is under 5 kHz anyway.

I think that when talking of the bandwidth of a transmitter you would be
saying 4.5 kHz (and not 9 kHz for the two times 4.5 kHz). So - what you are
saying is that the bandwidth in the US is 7.5 kHz only.  I dont think thats
the case - I am pretty much sure it's 9 kHz. I spoke to Harris Corp. a
couple of days ago and they confirmed that AM transmitters in the US are
always 9 kHz bandwidth.

Anyway thanks for your responce !!

Best 73's
Stig Hartvig Nielsen
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