Frank Dresser wrote:

It's not quite as simple as that. All broadcast audio is processed.
Here's
a brief history:

http://www.bext.com/histproc.htm

Clear Channel is adopting IBOC and has developed a coincidental
interest in
reducing the bandwidth of AM audio:

http://www.rwonline.com/reference-ro...andwidth.shtml


There might also be a station to station difference. Stations can
process
their audio differently.

Frank Dresser
---------------------------------------------------
I am aware of "standard" audio processing, but the refference giving
75uS on AM through me for a minor loop. Up too long and the old brain
was a little too fogged. I tried several local AM stations with 75uS
and 50uS
and they soundeed very muffled. The exact oppositte of what I am trying
to do.

I do remember when WLW (700KHz) used to run real clasical music
programs on Sunday afternoon, and they clearly broadcast up to at least
10KHz. The cymbols were crystal clear. But that was 35~40 uears ago.

Terry

wrote in message
oups.com...

I am aware of "standard" audio processing, but the refference giving
75uS on AM through me for a minor loop. Up too long and the old brain
was a little too fogged. I tried several local AM stations with 75uS
and 50uS
and they soundeed very muffled. The exact oppositte of what I am trying
to do.


You need to have a IF about 20 kHz wide to hear the preemphasis.



I do remember when WLW (700KHz) used to run real clasical music
programs on Sunday afternoon, and they clearly broadcast up to at least
10KHz. The cymbols were crystal clear. But that was 35~40 uears ago.

Terry


No doubt. I remember the adjacent channel splatter some stations would put
out back in the late 60s and early 70s. I don't think there was a specific
FCC AM bandwidth restriction back then, the stations were just mandated to
limit interference. The FCC's minimum separation between stations in the
same market was 30 kHz, and some stations might broadcast a full 15 khz of
audio.

When the FCC reduced the channel spacing to 20 kHz in the same market they
also made a 10 kHz audio bandwidth limit official.

You could also bring this topic up in rec.radio.broadcasting. There are a
few broadcast pros there who have hands-on transmitter expirence.

Frank Dresser

wrote in message
oups.com...

I am aware of "standard" audio processing, but the refference giving
75uS on AM through me for a minor loop. Up too long and the old brain
was a little too fogged. I tried several local AM stations with 75uS
and 50uS
and they soundeed very muffled. The exact oppositte of what I am trying
to do.


Here ya go, straight from the National Radio Systems Committee:

http://www.nrscstandards.org/Standards/nrsc-1.pdf

However, in the section labeled "scope", there's a sentence which reads:

"Compliance with the standard is strictly voluntary."

Frank Dresser

Frank Dresser wrote:

Here ya go, straight from the National Radio Systems Committee:

http://www.nrscstandards.org/Standards/nrsc-1.pdf

However, in the section labeled "scope", there's a sentence which
reads:

"Compliance with the standard is strictly voluntary."

Frank Dresser
----------------------------
Thanks for the link. It is nice to find out the FCC even has errors
in their technical archive.

Terry

wrote in message
oups.com...

Thanks for the link. It is nice to find out the FCC even has errors
in their technical archive.

Terry


What was the FCC's error?

Frank Dresser

I will have to find the link, but last night I was digging around in
their
technical archives and I found a statement to the effect:"All domestic
AM BCB transmitters shall use a 75Us preemphaisis." I was looking
for the maximum analog BW a AM/MW station could use."

In the good old days class A stations could go with, I think up to
15KHz BW. I didn't feel like going to my parents and digging
through the 1955~1970 Popular Electroncs that had an article
on this issue.

I am trying to decide if I want to add a ~10KHz ceramic filter to
my outboard detector.
My fitler line up lloks like it will be:
500HZ crystal filter
2.1KHz crystal filter
3.8KHZ ceramic filter
5KHz ceramic filter
8 or 10KHz ceramic filter
(15KHz crystal filter for FM only!).
The FM will be designed and added later.

The audio will have 2 tilt tone control sections,
similar but with different pivot points. The first
centered at 700, the 2nd at ~1.4KHz. I hope to
decide if I can use one fitler with an ocatave
function, or if 2 fitlers in series will be better.
I would like to keep this simple enough for
someone other then me to use.

I am leaving the original audio chain in the R2000s
intact so that at there very least my wife will able to
use the "listening post".

A friend bought some "exotic" eletronic stuff from a
local engineering firm that went out of business.
Amoung the items were several NEDSP DSP
modules. See:
http://www.bhinstrumentation.co.uk/html/nedsp1061.html
I am trying to trade him out of at least one.
They are tiny, powerfull and don't mangle the audio
"too" much.

My "simple" outboard detector is undergoing
"mission creep".

Terry

wrote in message
oups.com...
I will have to find the link, but last night I was digging around in
their
technical archives and I found a statement to the effect:"All domestic
AM BCB transmitters shall use a 75Us preemphaisis." I was looking
for the maximum analog BW a AM/MW station could use."

My information might be outdated. Subjectively, though, I think I hear
differences in different stations. I suppose other factors in the
processing might account for any differences.



In the good old days class A stations could go with, I think up to
15KHz BW. I didn't feel like going to my parents and digging
through the 1955~1970 Popular Electroncs that had an article
on this issue.

I'm almost certain that's true. Even 10 kHz of good audio isn't bad, but I
don't hear much of that nowadays.



I am trying to decide if I want to add a ~10KHz ceramic filter to
my outboard detector.

That only allows 5 kHz for normal DSB AM. Will you be limiting the wideband
demodulation to the sync detector?


[snip]

Frank Dresser

On Sun, 26 Jun 2005 18:33:04 GMT, "Frank Dresser"
wrote:

Sec. 73.44 AM transmission system emission limitations.



(a) The emissions of stations in the AM service shall be attenuated
in
accordance with the requirements specified in paragraph (b) of this
section. Emissions shall be measured using a properly operated and
suitable swept-frequency RF spectrum analyzer using a peak hold
duration of 10 minutes, no video filtering, and a 300 Hz resolution
bandwidth, except that a wider resolution bandwidth may be employed
above 11.5 kHz to detect transient emissions. Alternatively, other
specialized receivers or monitors with appropriate characteristics
may
be used to determine compliance with the provisions of this
section,
provided that any disputes over measurement accuracy are resolved
in
favor of measurements obtained by using a calibrated spectrum
analyzer
adjusted as set forth above.

(b) Emissions 10.2 kHz to 20 kHz removed from the carrier must be
attenuated at least 25 dB below the unmodulated carrier level,
emissions 20 kHz to 30 kHz removed from the carrier must be
attenuated
at least 35 dB below the unmodulated carrier level, emissions 30
kHz
to 60 kHz removed from the carrier must be attenuated at least [5 +
1
dB/kHz] below the unmodulated carrier level, and emissions between
60
kHz and 75 kHz of the carrier frequency must be attenuated at least
65
dB below the unmodulated carrier level. Emissions removed by more
than
75 kHz must be attenuated at least 43 + 10 Log (Power in watts) or
80
dB below the unmodulated carrier level, whichever is the lesser
attenuation, except for transmitters having power less than 158
watts,
where the attenuation must be at least 65 dB below carrier level.

(c) Should harmful interference be caused to the reception of other
broadcast or non-broadcast stations by out of band emissions, the
licensee may be directed to achieve a greater degree of
attentuation
than specified in paragraphs (a) and (b) of this section.

http://kauko.hallikainen.org/FCC/FccRules/2005/73/44/

Frank Dresser wrote:

That only allows 5 kHz for normal DSB AM. Will you be limiting the
wideband
demodulation to the sync detector?

[snip]

Frank Dresser
---------------------------------------
I meant 20KHz for 10KHz recovered audio bandwidth.
I have some nice, but wide older Murata ceramics I salvaged
30 years ago from a (then) high end Kenwood tuner AM section.
I have them in a 35mm film cansiter labled 10KHZ. Sorry for
the sloppy thinking. It had a wide/HiFi positions as well as a
naorrow/distant positon. The "narrows" are like barn doors,
maybe 14~15 wide fora 6~7KHz signal, and the "wides" are
~21 wide giving just over 10KHz.

In a way it will be nice to use all this junk I have saved for the
last 3 decades.

Terry

In article ,
"Frank Dresser" wrote:

wrote in message
oups.com...
I will have to find the link, but last night I was digging around
in their technical archives and I found a statement to the
effect:"All domestic AM BCB transmitters shall use a 75Us
preemphaisis." I was looking for the maximum analog BW a AM/MW
station could use."

My information might be outdated. Subjectively, though, I think I
hear differences in different stations. I suppose other factors in
the processing might account for any differences.



In the good old days class A stations could go with, I think up to
15KHz BW. I didn't feel like going to my parents and digging
through the 1955~1970 Popular Electroncs that had an article on
this issue.

I'm almost certain that's true. Even 10 kHz of good audio isn't bad,
but I don't hear much of that nowadays.



I am trying to decide if I want to add a ~10KHz ceramic filter to
my outboard detector.

That only allows 5 kHz for normal DSB AM. Will you be limiting the
wideband demodulation to the sync detector?

The best sounding radio I ever had was to connect a good audio
amplifier and speakers up to a crystal radio. There were several local
stations that were very strong signal on this radio and it sounded
fantastic. Never heard anything better since. This was using a real
crystal and cat whisker not a diode in a package. Not much there to
limit the audio response except the Q response curve of the tank
circuit. No filters at all just antenna wire and ground into the tank
circuit followed by the detector and then audio amplifier with speaker.
No need for a fancy design.

--
Telamon
Ventura, California