In the US AM broadcast stations are limited to less than
10 kHz audio bandwidth. This did not used to be true, but it is
today.

Doug McDonald

Agamemnon wrote:
"DAB sounds worse than FM" wrote in message

You wouldn't take the test, so I owe you no apology whatsoever, and
I'd like to know whether you've donated the agreed £10 to the
Tsunami appeal?

I took the original test and I got them all right even though it was
not completely fair on me as I pointed out at the time. Your second
test was completely unscientific and deliberately weighted against
me as can be seen from the EBU
Technical Review which details how a genuine scientific test should
be carried out.

I'm still waiting for your apology.


You admitted that you only identified the CD-original sample by
viewing the sample's frequency response and you've admitted that you
keep Dolby

You downright DECEITFUL LIAR !!!!

I said nothing of the kind. What I told you was that is was easy to
work out the original since the difference in frequency responses is
clearly audible.


I quote:

"LOL.... All Agamemnon has to do to spot the uncompressed file is to
switch
on his Dolby Surround Pro-Logic II decoder and set it to Movie. So why
should he waste his time downloading 40MB of crap."


Digital switched-on, which helps to identify the MPEG-encoded
samples. This test was therefore declared null and void.

POPPYCOCK. I did nothing of the kindwith the original samples you
posted.
You are a downright DECEITFUL LIAR !!!!


I quote:

"LOL.... All Agamemnon has to do to spot the uncompressed file is to
switch
on his Dolby Surround Pro-Logic II decoder and set it to Movie. So why
should he waste his time downloading 40MB of crap."


You then refused to take a test where the bandwidths of the samples
were all similar due to lowpass filtering. Therefore, just like a
football

Because you are a CHEAT ! That is not how official scientific
listening test are conducted and that is why you still owe me an
apology.


"You: Oh really. If you are still filtering the encoded sample at
15.5khz
the test is completely unscientific and meaningless.


Me: For the UMPTEENTH time, the digital radio stations on DAB, DTT and
probably DSat and cable lowpass filter with a cutoff frequency of
between 15.5kHz to 16kHz. This test is meant to emulate the performance
of the MP2 codec for audio as might be expected on digital radio.

Therefore, there is nothing unscientific or meaningless about this
test."


team that doesn't turn up to a match forfeits the game, you fail the
test, and owe the tsunami appeal £10, as agreed.

You will never receive an apology, because I have nothing to
apologise for.

You're a technical incompetent and a known and regular troll and
buffoon.

CHEAT, LIAR, CHARLETON !



£10 to the tsunami appeal and admit that you cannot pass the test.


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview, DAB & MP3 Player Prices:
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http://www.digitalradiotech.co.uk/mp...e_capacity.htm

DAB sounds worse than FM wrote:

[snip]

You're doing it again Steve! It seems he's got just as much time to
argue as you, unfortunately.

Anyway, what the American's allow and what happens in Europe are two
completely separate things. It's perfectly correct that, within a 9kHz
channel, using DSB, you can only have a 4.5kHz bandwidth - the point is
that in the USA they're allowed to stray _beyond_ their 10kHz channel
because of different attitudes to (and regulation of) frequency
planning.

I don't know what the regulation states in the UK (though it must be on
the OfCom website somewhere, surely?) but it's quite clear that all the
UK AM broadcasts I've ever received on a radio with selectable
filtering have a broadcast low pass filter around 4-5kHz - apart from
Radio 4 LW which seems to cut off even lower.

I didn't follow why you were having this argument - was it yet another
one started by our (now sadly resident) troll?

If you don't post a reply Steve, neither will he - it's how we got rid
of him last time.

Cheers,
David.

CHEAT, LIAR, CHARLETON !

Objection! that's Charlatan
--
Tony Sayer

In article .com,
writes
DAB sounds worse than FM wrote:

[snip]

You're doing it again Steve! It seems he's got just as much time to
argue as you, unfortunately.

Anyway, what the American's allow and what happens in Europe are two
completely separate things. It's perfectly correct that, within a 9kHz
channel, using DSB, you can only have a 4.5kHz bandwidth - the point is
that in the USA they're allowed to stray _beyond_ their 10kHz channel
because of different attitudes to (and regulation of) frequency
planning.

I don't know what the regulation states in the UK (though it must be on
the OfCom website somewhere, surely?)

http://www.ofcom.org.uk/codes_guidel...o/codes/engine
ering_code.pdf

--
Tony Sayer

wrote:

[snip]

UK AM broadcasts I've ever received on a radio with selectable
filtering have a broadcast low pass filter around 4-5kHz - apart from
Radio 4 LW which seems to cut off even lower.

Someone somewhere on Usenet said this was because the aerial system at
Droitwich has a rather high Q ?

tony sayer wrote:
In article .com,
writes

I don't know what the regulation states in the UK (though it must be
on the OfCom website somewhere, surely?)

http://www.ofcom.org.uk/codes_guidel...o/codes/engine
ering_code.pdf


Have you seen the wording of 3.2 Spectral Occupancy:

"3 . 2 Spectral Occupancy
Sidebands must not exceed a level with respect to the steady state
carrier, of:
.. 20dB for sideband components more than ± 7.5 kHz from nominal carrier
frequency.
.. 40dB for sideband components more than ± 9 kHz from nominal carrier
frequency.
These limitations are to be achieved by the use of audio low-pass
filters."

That wording means that the signal can be 20dB *up* at 7.5kHz and 40dB
up at 9kHz.

Shorely shum mishtake?


--
Steve - www.digitalradiotech.co.uk - Digital Radio News & Info

Find the cheapest Freeview, DAB & MP3 Player Prices:
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http://www.digitalradiotech.co.uk/mp...e_capacity.htm

In message
tony sayer wrote:

In article .com,
writes
DAB sounds worse than FM wrote:

[snip]

You're doing it again Steve! It seems he's got just as much time to
argue as you, unfortunately.

Anyway, what the American's allow and what happens in Europe are two
completely separate things. It's perfectly correct that, within a 9kHz
channel, using DSB, you can only have a 4.5kHz bandwidth - the point is
that in the USA they're allowed to stray _beyond_ their 10kHz channel
because of different attitudes to (and regulation of) frequency
planning.

I don't know what the regulation states in the UK (though it must be on
the OfCom website somewhere, surely?)

http://www.ofcom.org.uk/codes_guidel...o/codes/engine
ering_code.pdf

That relates only to local radio, but I see that it allows a
nominal audio bandwidth on AM of 6kHz -- which straight away
takes us beyond Steve's supposed 9kHz channel width.

Steve has assumed that channel spacing defines (or implies) the
channel width -- but there are plenty more cases where it
doesn't. GSM is one example, but a more extreme one is 802.11
wireless LAN, where (AFAICR) you'll find your access point allows
you to choose from up to 13 channels, yet only about four of them
are genuinely independent and non-overlapping.

--
Richard L.

In article , DAB sounds worse than
FM wrote:
X-posted to uk.rec.audio hopefully to attract Jim Lesurf's attention.

OK. Although I'm not sure I can provide all the info you may require...
:-)


and your (totally incorrect) assertion about MW allowing a frequency
response in the UK of 9kHz is incorrect:

Poppycock.

Look at the encoder and transmitter technical specifications

http://www.transmittersrus.com/inovo_222.htm

(pre-emphasis defeated): "PROOF" mode: ±0.5dB, 10Hz-15kHz 222-00
(NRSC): ±1dB, 10Hz-9.7kHz 222-01 (Euro MW): ±1dB, 10Hz-8.7kHz 222-02
(US SW): ±1dB, 10Hz-6.2kHz 222-03 (Int'l SW): ±1dB, 10Hz-4.85kHz


Can't comment on the above as I don't know the official limits in various
areas around the world, for various purposes. However it may be worth
bearing in mind that a TX may be specced to exceed what is legally
permitted in a given area in order to ensure that - when combined with what
feeds it - the results are not excessively limited in performance.

Hence I assume you can buy TX/modulators with a given specified max
bandwidth, but this does not mean you don't have to filter the input for
use in a given area/application.



You can have virtually any frequency response you like on medium wave.
From the tech speacs above you can see that in PROOF mode its up to
15kHz, and you can always go higher. Weather the tuner lets you decode
it is another thing. Solution. Build your own.

In any given political/geographic area there will be legally enforced
limits on the transmission bandwidth, etc, which is allowed for a given
purpose. You can obviously build items that exceed this, but it may not be
legal to use them


Broadcast MW uses envelope AM. MW receivers use envelope detectors.
Envelope AM is inherently double-sideband, so the maximum audio
bandwidth will be 4.5kHz.

My understanding is that in the UK (and in the EBU area) the 'medium wave'
(HF) broadcasts that use AM are legally permitted under a set of
requirements which include:

1) That the carrier frequencies are all nominally integer multiples of
9kHz.

2) That the channels allocated are centered on these and are nominally 9kHz
wide in total. i.e. extend +/- 4.5 kHz either side of the assigned carrier
frequency.

3) That modulation is essentially limited to be restricted to this
allocated transmission bandwidth. I don't know the current specs, but I
assume they come from the EBU/WRC agreements. I assume they mean that
any transmitted power has to be well below a given level once you reach or
exceed +/- 4.5 kHz from carrier. I think the actual limit frequency is set
lowe than this for 'guard' purposes.

4) So far as possible, nearby transmitters are given carrier frequencies
and channels that are no closer than 'alternate'. i.e. the attempt is made
to avoid people having two signals of similar power in adjacent channels,
or on the same channel. Alas, HF being 'promiscuous' this tends not to work
amazingly well. :-)

5) That simple AM is the standard method used for 'medium wave'
broadcasting (and also 'long wave'). This produces symmetric sidebands, so
means the nominal audio bandwidth should not exceed 4.5 kHz. I think the
actual limit is less than this for 'guard' purposes. Allowing higher
modulation frequencies would mean spilling into a total of *three*
channels, so I would be surpised if this is permitted unless the
'spillover' power levels are attenuated by a significant factor at
transmission.

However the actual specifications have varied with time. So a few decades
ago some european 'medium wave' stations broadcast using a wider
transmission bandwidth, but this has been stopped as it increases
interference problems.

Also, other specs are nominally permitted. Obvious examples being things
like Rugby time signals which are not intended as audio broadcasting.

For various historic reasons I think the situation in other world areas is
different in some details. e.g. IIRC Africa (?) used (uses?) 8 kHz carrier
spacing and channel bandwidths. So the USA may use 10 kHz for all I know.
My recollection is that 9 kHz is now widespread as the standard.

However where the band is crowded I'd expect people to be required to only
transmit with a transmission bandwidth of one allocated channel. Otherwise
the interference problems become much worse. For simple AM this means
limiting the modulation (audio) bandwidth to half the transmission
bandwidth or half the nominal carrier spacing.

To determine the precise details someone would have to get the relevant
specs from the WRC/EBU/Ofcom or whoever represent the permission
authorities for a given area/application.

All the above is to the best of my recollection. If it is wrong, someone
can point me at the relevant WRC/EBU/FCC/etc official documents for the
currently enforced specs.

Slainte,

Jim

--
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In article , Arny Krueger
wrote:


The above audio was recorded from my Denon TU260L Mk1 FM/AM tuner.

I'd feel a little better if I knew that the 4500 Hz near brick-wall
filter your sample suggests was no way contributed to by the receiver.

I'd assume that the RX is filtering, but my understanding is that this is
on the basis that no modulation is to be expected outwith this band.

Slainte,

Jim

--
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