Earl Kiosterud wrote:

Synchronous AM demodulation uses a locally regenerated carrier, fed along with the AM signal
(upper or lower set of sidebands) to a multiplier (modulator). The result is the audio. It
replaces the envelope (diode) detector usually used. You can think of it as another superhet
stage where the result, instead of another IF frequency, is the baseband audio. That's
because the local oscillator is the same frequency as the carrier of the (IF) signal, so the
difference is zero. The sidebands wind up translated to baseband audio instead of to
another IF frequency.

There are advantages. Since one set of sidebands or the other can be used, if there's a
distant station 10KHz away, causing that AM whistle, you just switch to the other set of
sidebands, whichever comes in the cleanest. Also, it doesn't depend on proper amplitude and
phase of both sets of sidebands to work properly, as does the regular envelope detector, so
it works better with impaired signals.



I only understood about 75% of what your wrote, but if I understand
your meaning, this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

"SFTV_troy" blabbed:
... this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

At least in the States, AM & FM broadcasting is limited to 50 Hz to 15KHz.

Digital broadcasting is limited to under 20 Hz to over 20KHz, or basically,
the extent of the normal human hearing range.

If you're listening to 100 to 6,000 Hz, you're listening to a poor telephone
connection.

SoCal Tom

On Sun, 30 Sep 2007 13:48:23 -0700, "SoCal Tom"
wrote:

If you're listening to 100 to 6,000 Hz, you're listening to a poor telephone
connection.

100Hz to 6000Hz would be an unbelievably good telephone connection.
300 to 3000 is more like a normal one.

d

--
Pearce Consulting
http://www.pearce.uk.com

"SoCal Tom" wrote in message
...

"SFTV_troy" blabbed:
... this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

At least in the States, AM & FM broadcasting is limited to 50 Hz to 15KHz.

AM is restricted by the NRSC standard to a 10 kHz brick wall.

Digital broadcasting is limited to under 20 Hz to over 20KHz, or
basically, the extent of the normal human hearing range.

If you're listening to 100 to 6,000 Hz, you're listening to a poor
telephone connection.

Bob Orban, on the NRSC committee, found that consumer radios almost without
exception, rolled off by at least 10 db by 4.2 kHz, and passed practically
nothing over 5 kHz.

On Sep 30, 3:09 pm, "David Eduardo" wrote:
"SoCal Tom" wrote in message

...



"SFTV_troy" blabbed:
... this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

At least in the States, AM & FM broadcasting is limited to 50 Hz to 15KHz.

AM is restricted by the NRSC standard to a 10 kHz brick wall.



Digital broadcasting is limited to under 20 Hz to over 20KHz, or
basically, the extent of the normal human hearing range.

If you're listening to 100 to 6,000 Hz, you're listening to a poor
telephone connection.

Bob Orban, on the NRSC committee, found that consumer radios almost without
exception, rolled off by at least 10 db by 4.2 kHz, and passed practically
nothing over 5 kHz.

Bob Orban is the alien from the late Weekly World News.

god darn it, we've had EVERY TROLL in the group except the K-Man, the
Scott Lifshine/Wereo entity, and the RRAP brigade in this thread!

Morein/McCarty/66.6% of the world's asshole postings has chimed in
even.

I predict the world will simply implode and then go back to whatever
it was doing beforehand.

In article ,
says...



"SFTV_troy" blabbed:
... this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

At least in the States, AM & FM broadcasting is limited to 50 Hz to 15KHz.

There is no low frequency limit for either AM or FM; 50 Hz was the minimum
performance standard that would meet the now long-deleted FCC Proof of
Performance measurements.

The effective HF limit on FM is about 18.5 kHz; this leaves a +/- 500 Hz guard
band for the stereo pilot tone. Again, 15 kHz was the minimum spec that would
pass a Proof of Performance, not a limit on bandwidth.

Currently, the legal FCC-mandated HF limit on AM in the US is a hair less than
10 kHz, which almost completely protects second-adjacent stations from
interference. This was changed around 1990 as a result of work done by the
National Radio Systems Committee (NRSC). More recent work by the NRSC has
indicated that 7 kHz is probably the optimum compromise between causing
interference and loss of audio quality on typical AM radios (which are down 3
dB at about 2.6 kHz). However, limiting bandwidth to 7 kHz is voluntary.

"Robert Orban" wrote in message
...
In article ,
says...



"SFTV_troy" blabbed:
... this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

At least in the States, AM & FM broadcasting is limited to 50 Hz to 15KHz.

There is no low frequency limit for either AM or FM; 50 Hz was the minimum
performance standard that would meet the now long-deleted FCC Proof of
Performance measurements.

The effective HF limit on FM is about 18.5 kHz; this leaves a +/- 500 Hz guard
band for the stereo pilot tone. Again, 15 kHz was the minimum spec that would
pass a Proof of Performance, not a limit on bandwidth.

Currently, the legal FCC-mandated HF limit on AM in the US is a hair less than
10 kHz, which almost completely protects second-adjacent stations from
interference. This was changed around 1990 as a result of work done by the
National Radio Systems Committee (NRSC). More recent work by the NRSC has
indicated that 7 kHz is probably the optimum compromise between causing
interference and loss of audio quality on typical AM radios (which are down 3
dB at about 2.6 kHz). However, limiting bandwidth to 7 kHz is voluntary.


Robert,

Was AM radio ever allowed audio to 15 KHz? I read many years ago that it was, perhaps
before the NRSC recommendation was adopted by the FCC. I presumed that the stations either
were allowed to overlap 5 KHz (doubtful), or that stations in a given area were separated by
at least 30 KHz.
--
Regards from Virginia Beach,

Earl Kiosterud
www.smokeylake.com

On Fri, 09 Nov 2007 15:59:17 GMT, "Earl Kiosterud"
wrote:

Was AM radio ever allowed audio to 15 KHz? I read many years ago that it was, perhaps
before the NRSC recommendation was adopted by the FCC. I presumed that the stations either
were allowed to overlap 5 KHz (doubtful), or that stations in a given area were separated by
at least 30 KHz.
--
Regards from Virginia Beach,

Earl Kiosterud
www.smokeylake.com



Years ago, here in London an interesting thing happened. Audio was fed
to our big AM transmitter by landline, which had a hopeless frequency
response, losing a great deal of HF. This was equalised in the channel
filter for the transmitter, resulting in flat AM out to about 5kHz.

Anyway, at some point the land line was replaced with a much better
one, but nobody thought to tweak the channel filter to suit the new
frequency response, resulting in audio which was flattish out to at
least 12 if not 15kHz. we had really good quality AM for quite a
while.

d

--
Pearce Consulting
http://www.pearce.uk.com

"Earl Kiosterud" wrote:



Robert,

Was AM radio ever allowed audio to 15 KHz? I read many years ago that it was, perhaps
before the NRSC recommendation was adopted by the FCC. I presumed that the stations either
were allowed to overlap 5 KHz (doubtful), or that stations in a given area were separated by
at least 30 KHz.


I'm not Robert, but...

Prior to FM multiplex stereo, there were some experimental stereo
broadcasters who transmitted one channel on FM and the other on AM. A
friend of mine has an old Lafayette tuner set up this way, along with
a plug-in jack for a multiplex adapter when they became available.

I think there was quite a large amount of effort to produce wideband
AM. Amplitude modulation itself certainly has no such limitations;
however it is possible that tuning the tower system to handle that
wide a bandwitdth within MW would be a problem. Don't know.


--
Eric F. Richards,
"It's the Din of iBiquity." -- Frank Dresser

"Earl Kiosterud" wrote in message
newst%Yi.403$CI1.60@trnddc03...


"Robert Orban" wrote in message
...
In article ,
says...



"SFTV_troy" blabbed:
... this new receiving technique would not improve the sound
(it would still be limited from 100-6000 hertz), but would only reduce
interference.

At least in the States, AM & FM broadcasting is limited to 50 Hz to
15KHz.

There is no low frequency limit for either AM or FM; 50 Hz was the
minimum
performance standard that would meet the now long-deleted FCC Proof of
Performance measurements.

The effective HF limit on FM is about 18.5 kHz; this leaves a +/- 500 Hz
guard
band for the stereo pilot tone. Again, 15 kHz was the minimum spec that
would
pass a Proof of Performance, not a limit on bandwidth.

Currently, the legal FCC-mandated HF limit on AM in the US is a hair less
than
10 kHz, which almost completely protects second-adjacent stations from
interference. This was changed around 1990 as a result of work done by
the
National Radio Systems Committee (NRSC). More recent work by the NRSC has
indicated that 7 kHz is probably the optimum compromise between causing
interference and loss of audio quality on typical AM radios (which are
down 3
dB at about 2.6 kHz). However, limiting bandwidth to 7 kHz is voluntary.


Robert,

Was AM radio ever allowed audio to 15 KHz? I read many years ago that it
was, perhaps before the NRSC recommendation was adopted by the FCC. I
presumed that the stations either were allowed to overlap 5 KHz
(doubtful), or that stations in a given area were separated by at least 30
KHz.
--
Regards from Virginia Beach,

Earl Kiosterud
www.smokeylake.com

I was a broadcast engineer in the late 1970s to the late 1980s. At that time
(before NRSC) AM was required to transmit a minimum 5KHz bandwidth, but the
maximum modulated bandwidth was not really defined. There were limits on
"spurious" emissions, caused by audio distortion products and carrier
harmonics. I don't recall the exact mask, but 15KHz was legal at that time.
Our studio transmitter link was a Mosely PCL-505, which was flat to 15KHz,
and we employed no artificial band limiting, so the station was flat to at
least 12KHz. Our tower was the limiting factor for bandwidth. It sounded
just like monophonic FM on the modulation monitor.

During the day there was no overlap, because stations were allocated on
second alternate channels in most markets. Local stations that did overlap
usually worked out a solution amongst themselves if the interference was
objectionable. At night it got quite a bit noisier as distant stations would
skip into the area, but it wasn't generally sidebands that caused the
problem, it was the carriers themselves, each whining away at 10KHz. That is
still a problem, even today.

The real problem was that in the late 1980s, AM stations began adding
proprietary "pre-emphasis" -- high frequency boost to make their station
sound brighter on typical pathetically band-limited AM receivers. This can
and did cause severe interference in some congested markets. Partially to
address this, and to standardize the pre-emphasis, NRSC limited AM sidebands
to 10KHz in the early 1990s. Since most AM radios do not even come close to
being flat to 5KHz, 10 KHz is still two or three times more bandwidth than
most listeners can use.