Floyd Davidson wrote:

opcom wrote:
Not studio quality.
Studio quality AM is +/- 5KHz.

"Studio quality AM" is not a valid term. AM Broadcast has never
been up to "Studio Quality" standards, which would be _at_
_least_ 20 to 20K Hz.

AM Broadcast Band quality is 5K Hz.

It's semantics at this point, the AM studio is perfect if it is limited to about 5KHz, something which is quite a different case than an FM studio or a recording studio.


+/- 3000-3500 Hz is communications quality, and fine for
AM. but we don't need more rules.

Why so wide?

I answer below..


SSB? 2.5KHz is fine. I am speaking up for the old iron. I do
limit my AM to +/-3KHz in the speech amp.

There is no difference at all between the audio response
necessary for SSB and AM. AM, because it has both sidebands,
will necessarily take up twice the RF spectrum for the same
audio response, but in fact 2.4KHz (400Hz to 2800Hz) is actually
*preferable* to higher fidelity audio response when the purpose
is voice communications. (Ma Bell did a bazillion studies on
this decades ago, so it is not exactly new information.)

Can you find this data for me? I am very interested, it might shed more light on the subject. I understand it may be hard to find today.

Since SSB has no carrier, you can shave the bandwidth a little closer by getting rid of the lower frequencies. With AM, you may as well use the lower frequencies if you want, since you have a carrier at 0 Hz so to speak. 2.4KHz
bandwidth on AM voice sounds a little muffled to me, and to me, 3.0KHz or (very) slightly more, is much more readable, especially when there is alot of noise. Everyone hears differently in some respect, maybe I have hearing
damage. In amy case I am not advocating more than 'necessary', but I do have trouble with speech signals that are cut off too sharply. I always tune my SSB receiver so that the voice is higher pitched than natural, then it is
easier for me to hear. It doesn't work with AM that way, the tuning.

just as an example,
2.4KHz ssb = 300 to 2700 Hz audio.
+/-2.4KHz AM = 0 to 2400 Hz audio.

I can't remember what volume I read it in so take it with a grain of salt, or a whole bag of salt, but I recall that for good intelligibility and having a signal that does not tire the operators, there was some mathematical
relationship between the highest and lowest audio frequencies to be reproduced. Anyone remember that? I regret I cannot quote the source. Maybe there is a some experimentation to be done. I would like to see a reprint of the
Bell studies.

But anyway, here are my sources to support the freedon to employ at least some leeway for bandwidth in the matter of communications quality AM. It's definitely your right to interpret them how you wish:

================================================== =======
"Understandable speech requires the reproduction of all
frequencies from about 250 to 2700 cycles, or sideband
frequencies ranging from 250 to 2700 cycles above and
below the carrier frequency."

FROM: "RADIO ENGINEERING", second edition, 1937, chapter 9,
section 72, page 396, "Waves with Amplitude Modulation",
Frederick Emmons Terman, Sc.D., Professor of Electrical
Engineering, Stanford University.

MY Opinion: Mr. Terman's text says 'requires',
therefore this is taken as the minimum requirement for
speech to be 'understandable'. This does not necessarily
imply good communications quality, but rather
'understandability'.

================================================== ==========

"Modulation frequencies Corresponding to Typical Signals
(minimum frequency range that must be met)"

"Long-distance telephone quality.......250-3500 c/s."

FROM: "RADIO ENGINEERING", third edition, 1947, chapter 9,
section 9-1, page 469, table 9-1 --Modulation frequencies
Corresponding to Typical Signals (minimum frequency range
that must be met)., Frederick Emmons Terman, Sc.D., Professor
of Electrical Engineering and Dean of theSchool of Engineering,
Stanford University. Past president, Institute of Radio Engineers.

My Opinion: Please consider the audio quality of long
distance telephone service in 1947.

================================================== ==========

"...For ordinary SSB telephony, M=3000 Hz. .."
"...For high quality SSB Telephony, M=4000Hz. ..."
"...For ordinary DSB telephony, M=6000 Hz. ..."
"...For high quality DSB Telephony, M=8000Hz. ..."

FROM: "THE RADIO MANUAL", fourth edition, 1950, appendix 5,
page 859, "Table of necessary bandwidths", George E. Sterling,
Commissioner, Federal Communications Commission, and
Robert B. Monroe, Radio Engineer, Columbia Broadcasting
System, D. Van Nostrand Company, Inc. 4th edition, 1950.

================================================== ===========

"Frequencies up to at least 2,500 cycles, and preferrably 3500
cycles, are necessary for good speech intelligibility."

FROM: "RADIO HANDBOOK", fourteenth edition, 1956, chapter 12,
section 12-1, page 225, Editors and Engineers, Ltd., edited by
William I. Orr, W6SAI.

================================================== ===========

"...Mediocre reproduction may be restricted to 100-5000 c/s.,
while many radio receivers are limited to 100-3500c/s. It
should be remembered that the frequency range is taken as
overall, including the loss of sidebands and including the
loudspeaker. Wide frequency range is only comfortable to
the listener so long as other forms of distortion are
negligible."

FROM: "THE RADIOTRON DESIGNER'S HANDBOOK, THIRD EDITION", 1941,
chapter 5, page 32, "frequency distortion", THE RADIOTRON
DESIGNER'S HANDBOOK, THIRD EDITION", F. Langford Smith,
S.SC., Member I.R.E, M. I.R.E., A.M.I.E.E., A.M.I.E

Floyd posted, in part:
There is no difference at all between the audio response
necessary for SSB and AM. AM, because it has both sidebands,
will necessarily take up twice the RF spectrum for the same
audio response, but in fact 2.4KHz (400Hz to 2800Hz) is actually
*preferable* to higher fidelity audio response when the purpose
is voice communications. (Ma Bell did a bazillion studies on
this decades ago, so it is not exactly new information.)
---------------------
I'd like to make a few comments about this.
1. AM does not necessarily have two sidebands. The same "quality" is had with
SSB AM and DSB AM, and SSB AM uses half the spectrum.

2. If the transmitted audio passband is 400 to 2800 Hz (2.4 kHz), the receiver
passband still needs to be 2.8 kHz for correct demodulation. That is, the
demodulation carrier must have the identical relationship to the sideband that
existed at the transmitter.

3. During WWII the Bell system used as little bandwidth as 1.6 kHz in their
long-haul channels. The quality was very poor, but you *could* communicate.
Modern telecom channel bandwidth is about 200 Hz to 3450 kHz. Generally this
is called a 3500 Hz channel. In ham radio that bandwidth provides good
fidelity for speech. With anything less it becomes increasingly difficult to
recognize who is the speaker. Using narrow band receive filters (1.8 to 2.4
kHz) improves the ability to communicate by eliminating or reducing QRM/QRN,
but the quality is reduced by this.

4. Ma Bell's studies on fidelity got into the perceptual area of balance
between the low end and high end of the audio spectrum; Having lots of bass
without good treble, or good treble without good base did not sound good.
That's one of the big reasons that the low end of the telecom voice channels
don't start at 100 Hz or lower. I thought I had a copy of the study, but
couldn't find it.

I would like to see hams who like AM migrate to SSB AM and limit the audio
passband to 3500 Hz. For carrierless SSB 3500 Hz should also be the passband
limit.

Don

opcom wrote:
Floyd Davidson wrote:

opcom wrote:
Not studio quality.
Studio quality AM is +/- 5KHz.

"Studio quality AM" is not a valid term. AM Broadcast has never
been up to "Studio Quality" standards, which would be _at_
_least_ 20 to 20K Hz.

AM Broadcast Band quality is 5K Hz.

It's semantics at this point, the AM studio is perfect if it is
limited to about 5KHz, something which is quite a different
case than an FM studio or a recording studio.

I doubt if many AM broadcast stations have studios that are
limited to 5KHz, any more than an FM station would. They
don't commonly go to the effort that a recording studio does,
but they certainly do not restrict fidelity to 5 KHz audio.

SSB? 2.5KHz is fine. I am speaking up for the old iron. I do
limit my AM to +/-3KHz in the speech amp.

There is no difference at all between the audio response
necessary for SSB and AM. AM, because it has both sidebands,
will necessarily take up twice the RF spectrum for the same
audio response, but in fact 2.4KHz (400Hz to 2800Hz) is actually
*preferable* to higher fidelity audio response when the purpose
is voice communications. (Ma Bell did a bazillion studies on
this decades ago, so it is not exactly new information.)

Can you find this data for me? I am very interested, it might
shed more light on the subject. I understand it may be hard to
find today.

I don't know where you'd be likely to find it. Perhaps in a large
science library.

Since SSB has no carrier, you can shave the bandwidth a little

You are talking apples, while I was talking oranges.

"There is no difference at all between the audio
response necessary for SSB and AM."

Audio response, not bandwidth. Clearly the bandwidth required
to get the same response is different for different modulation
schemes.

respect, maybe I have hearing damage. In amy case I am not
advocating more than 'necessary', but I do have trouble with
speech signals that are cut off too sharply. I always tune my
SSB receiver so that the voice is higher pitched than natural,
then it is easier for me to hear. It doesn't work with AM that
way, the tuning.

You would enjoy using the old Drake receivers, with a tunable
IF bandpass filter. You could locate the bandpass anywhere in
the audio range that suited your ears. (I also have hearing
loss, and when I was young I enjoyed music with a lot of bass
boost, while today I want the treble cranked up!)

But anyway, here are my sources to support the freedon to
employ at least some leeway for bandwidth in the matter of
communications quality AM. It's definitely your right to
interpret them how you wish:

================================================= ========
"Understandable speech requires the reproduction of all
frequencies from about 250 to 2700 cycles, or sideband
frequencies ranging from 250 to 2700 cycles above and
below the carrier frequency."

FROM: "RADIO ENGINEERING", second edition, 1937, chapter 9,
section 72, page 396, "Waves with Amplitude Modulation",
Frederick Emmons Terman, Sc.D., Professor of Electrical
Engineering, Stanford University.

MY Opinion: Mr. Terman's text says 'requires',
therefore this is taken as the minimum requirement for
speech to be 'understandable'. This does not necessarily
imply good communications quality, but rather
'understandability'.

That one seems to be a good interpretation of correct
information as it was understood at the time (1937).

================================================= ===========

"Modulation frequencies Corresponding to Typical Signals
(minimum frequency range that must be met)"

"Long-distance telephone quality.......250-3500 c/s."

FROM: "RADIO ENGINEERING", third edition, 1947, chapter 9,
section 9-1, page 469, table 9-1 --Modulation frequencies
Corresponding to Typical Signals (minimum frequency range
that must be met)., Frederick Emmons Terman, Sc.D., Professor
of Electrical Engineering and Dean of theSchool of Engineering,
Stanford University. Past president, Institute of Radio Engineers.

My Opinion: Please consider the audio quality of long
distance telephone service in 1947.

But that does not say anything about what is required for
communications. It just says what was provided by Ma Bell
in 1947, which is *not* something that was specified as the
best for communications (over a single channel).

The 250-3500 Hz range was what L carrier (over either coax cable
or what was then the newly designed and soon to be implemented
TD-2 microwave systems) provided on a per channel basis. But an
actual circuit connection was expected to be implemented with
_multiple_ tandem channels... and the ultimate circuit
connection provided was (and still is today) specified at 400 to
2800 Hz. (And believe me, too many L carrier channels in tandem
could make 400-2800 look good!)

The quality required end-to-end was a 400-2800 Hz channel
(with an SNR of 24 dB or better).

================================================= ===========

"...For ordinary SSB telephony, M=3000 Hz. .."
"...For high quality SSB Telephony, M=4000Hz. ..."
"...For ordinary DSB telephony, M=6000 Hz. ..."
"...For high quality DSB Telephony, M=8000Hz. ..."

FROM: "THE RADIO MANUAL", fourth edition, 1950, appendix 5,
page 859, "Table of necessary bandwidths", George E. Sterling,
Commissioner, Federal Communications Commission, and
Robert B. Monroe, Radio Engineer, Columbia Broadcasting
System, D. Van Nostrand Company, Inc. 4th edition, 1950.

Obviously that is in very round numbers and it does not
appear they meant them to be take as a specification.

In 1950 *nobody* expected to get such (4KHz audio) a "high
quality" signal over *any* long distance facility.

================================================= ============

"Frequencies up to at least 2,500 cycles, and preferrably 3500
cycles, are necessary for good speech intelligibility."

FROM: "RADIO HANDBOOK", fourteenth edition, 1956, chapter 12,
section 12-1, page 225, Editors and Engineers, Ltd., edited by
William I. Orr, W6SAI.

Mr. Orr was pretty good with the design of linear amplifiers.

================================================= ============

"...Mediocre reproduction may be restricted to 100-5000 c/s.,
while many radio receivers are limited to 100-3500c/s. It
should be remembered that the frequency range is taken as
overall, including the loss of sidebands and including the
loudspeaker. Wide frequency range is only comfortable to
the listener so long as other forms of distortion are
negligible."

FROM: "THE RADIOTRON DESIGNER'S HANDBOOK, THIRD EDITION", 1941,
chapter 5, page 32, "frequency distortion", THE RADIOTRON
DESIGNER'S HANDBOOK, THIRD EDITION", F. Langford Smith,
S.SC., Member I.R.E, M. I.R.E., A.M.I.E.E., A.M.I.E

That doesn't seem to apply to the subject at hand. It doesn't
say anything specific, but it does touch on one point that does
need to be considered: The amplitude distortion requirements
vary with the amount of other types of distortion or noise.

Hence processed audio might need less bandwidth to be effective,
and otherwise distorted audio might need more bandwidth to be
effective.


I looked through the texts that I have (virtually all telecom
related, as opposed to radio communications in general) and
did not find anything useful. I was struck by one odd thing
that is interesting though! Everything I found was concerned
not with audio bandwidth, but *only* with reduction of the
RF bandwidth... by finding better ways to encode that imaginary
0-4 KHz telephone channel into a digital data stream that uses
less bandwidth when it modulates an RF carrier.

Maybe we are all barking up the wrong tree, and should instead
be considering ways to use digital technology to put more signals
into the same HF bandwidth?

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"Larry" wrote:
Floyd,

I think it all boils down to this, if you want to limit the frequency range
of your radio to whatever, because you believe that you like it best (or
whatever) great! It is your privelege to do that. As for me, I think that a
little wider is nicer and that's OK for me too. You may believe strongly in
your justification but the rules give very wide lattitude in making this
call to the amateur. Some may think this is about to change but I don't
think so. So good luck and have fun. The hobby is great, isn't it!

I did not suggest that there should be a regulatory limit. That
came from elsewhere. My argument is purely one of technical
aspects that have to be considered.

However, if you and others insist on ignoring the appropriate technical
aspects, we *will* see regulatory action to curtail it.

By the way, in the discussion of bandwidths, your hyperbole is totally
without meaning if you are not specifying attenuation at the given limits of
bandwidth. 100 to 3500 hz is a very different spec if those are 3 db points
than if they are 26 or 60 db points. Also specifying that the limits refer
to peak or average would be helpful in making your comments meaningful.

Yes, and I could write a ****ing book too. What's your point?
The only time any specs that I meantioned deviated from the
standard ones, I mentioned not only that it did but what the
effect was.

Besides not even a moose would take his call at being real with those kinds
of limits. You're up there, go ask one!

If you want your audio to attract moose, please get a bullhorn
and head for the woods. But stay off the ham bands with it.


While you are at it... Learn not to top post and learn to trim
unnecessary quoted text. Bandwidth is important in places other
than a ham rig too.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

Floyd,

Being up there in Alaska isn't doing you much good. Sounds like you're not
getting any. Tell you what, get your bullhorn, go out in the woods, call a
moose .. hope for a female naturally .. well maybe not and maybe that's part
of the problem, and come back to the group with a whole lot better attitude.
Frankly people like you worry me with all that unfriendy hostility. You
sound like an immature young stud who just need to mellow out.

Oh BTFW Floyd, I'll post how and when I like and I'll leave any text
attached that I think may be appropriate and when it becomes your newsgroup
and you are made God, I might listen! Till then FO!!


"Floyd Davidson" wrote in message
...
"Larry" wrote:
Floyd,

I think it all boils down to this, if you want to limit the frequency
range
of your radio to whatever, because you believe that you like it best (or
whatever) great! It is your privelege to do that. As for me, I think that
a
little wider is nicer and that's OK for me too. You may believe strongly
in
your justification but the rules give very wide lattitude in making this
call to the amateur. Some may think this is about to change but I don't
think so. So good luck and have fun. The hobby is great, isn't it!

I did not suggest that there should be a regulatory limit. That
came from elsewhere. My argument is purely one of technical
aspects that have to be considered.

However, if you and others insist on ignoring the appropriate technical
aspects, we *will* see regulatory action to curtail it.

By the way, in the discussion of bandwidths, your hyperbole is totally
without meaning if you are not specifying attenuation at the given limits
of
bandwidth. 100 to 3500 hz is a very different spec if those are 3 db
points
than if they are 26 or 60 db points. Also specifying that the limits
refer
to peak or average would be helpful in making your comments meaningful.

Yes, and I could write a ****ing book too. What's your point?
The only time any specs that I meantioned deviated from the
standard ones, I mentioned not only that it did but what the
effect was.

Besides not even a moose would take his call at being real with those
kinds
of limits. You're up there, go ask one!

If you want your audio to attract moose, please get a bullhorn
and head for the woods. But stay off the ham bands with it.


While you are at it... Learn not to top post and learn to trim
unnecessary quoted text. Bandwidth is important in places other
than a ham rig too.

--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

"Larry" wrote:
Floyd,

Being up there in Alaska isn't doing you much good. Sounds like you're not
getting any. Tell you what, get your bullhorn, go out in the woods, call a
moose .. hope for a female naturally .. well maybe not and maybe that's part
of the problem, and come back to the group with a whole lot better attitude.
Frankly people like you worry me with all that unfriendy hostility.

In other words, you don't have a valid response, and can only come up
with "go call a moose".

You
sound like an immature young stud who just need to mellow out.

*You* are the one posting "go call a moose" responses, kid.

Oh BTFW Floyd, I'll post how and when I like and I'll leave any text
attached that I think may be appropriate and when it becomes your newsgroup
and you are made God, I might listen! Till then FO!!

You don't have a clue about Usenet either, do you. Take a look
at *any* of the thousands of Usenet guides on formatting articles.
Take a look at RFC-1855. Do a google search on "netiquette".

Nobody made me god, and that has nothing to do with your arrogant
ignorance of what works and what doesn't, on Usenet or on ham radio.


"Floyd Davidson" wrote in message
...


While you are at it... Learn not to top post and learn to trim
unnecessary quoted text. Bandwidth is important in places other
than a ham rig too.


--
Floyd L. Davidson http://web.newsguy.com/floyd_davidson
Ukpeagvik (Barrow, Alaska)

As to SSB AM, (called "AM Equivalent" by the military) some radios will do this, but others won't.

The military surplus GRC-106 for instance does this, and the final is a linear amplifier with associated efficiency issues. To the listener, it sounds like AM, but they can tell that a sideband is missing if they tune around.

The Johnson Viking for instance does not do it, and the final is a class-C stage modulated by a class AB2 push-pull stage.

So some gear just can't do it. I don't prefer linear amplifiers as final stages for AM, but it's an opinion.

There is nothing wrong with either mode. SSB AM can be used in the AM nets along with DSB AM.

FO! ??

Flash Override -the FO key function on some military field phones.



... Till then FO!!

In article , Floyd Davidson
writes:

"Studio quality AM" is not a valid term. AM Broadcast has never
been up to "Studio Quality" standards, which would be _at_
_least_ 20 to 20K Hz.

Hey, even FM Broadcast is only up to 15 KC. At least that's been the limit
since they added the stereo subcarrier. I agree that recording equipment
should be good at least up to 20 K.


There is no difference at all between the audio response
necessary for SSB and AM. AM, because it has both sidebands,
will necessarily take up twice the RF spectrum for the same
audio response, but in fact 2.4KHz (400Hz to 2800Hz) is actually
*preferable* to higher fidelity audio response when the purpose
is voice communications. (Ma Bell did a bazillion studies on
this decades ago, so it is not exactly new information.)

During my years at Bell Labsm, working in speech coding, our preferred standard
range was 300 - 3300 Hz. At 3300 you have a fighting chance of telling an "F"
from an "S" and a "T" from a "D" sound. At 4000 you have very little trouble.
At 2800 you have all those military types spelling it out with phonetics and
lots of "say again".

The low, bass end doesn't really affect BW much (not at all in AM with
carrier), but too much bass wastes power and voltage swings in the modulator,
and overlaods and distorts in the receiver's audio circuits and speaker, and
also batters your ears. That's why a lot of radios have tone switch
positionsthat cut out some of the bass response. 73, Mike K.




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