Dbowey wrote:
Several thousand unused AM rigs for six meters, and many MHz of
unused VHF spectrum.


Government agencies are hurting for spectrum. Now that the ARRL is under
Homeland Security you need to be thinking about the big frequency grab they are
getting ready to pull. It's far easier to take spectrum from the amateur radio
service than it is to force government agencies to make better use of what they
already have. You are first going to see the ARRL roll over for their new
boss, and give up some of 2 Meters. There are already people there who think
of 2M as "channelized."

Government agencies are hurting bigtime for UHF spectrum, and to a lesser
extent for VHF spectrum. But there is a huge amount of stuff in the HF
bands which is allocated for commercial and government use, which is no
longer used at all. Likewise the VHF-LO business band is mostly dead, and
right now you can get nationwide licenses for VHF-LO channels for a few
hundred bucks at auction.

I'd be happy to trade a chunk of 2M for an equivalent chunk of the VHF-LO
business band. What is going on is not that there is an increasing demand
for channels, but that the demand has changed. 800 MHz is crowded as hell
and everybody wants a chunk. 12 MHz is dead and nobody wants any.

The ARRL should be petitioning to grab some frequencies of our own.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

opcom wrote:
Hmm.. I suppose I could amplitude-modulate my Link 250-UFS 6M FM rig.

There is a LOT of AM aircraft radio gear out there which is currently
not legal for use because of the new narrowband channel allocations for
aircraft use. Those radios are basically available for the asking at your
local avionics shop.

And those radios are no problem to convert over to 2M AM. 6M wouldn't be
so easy.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

"opcom" wrote in message
...
Not studio quality.
Studio quality AM is +/- 5KHz.


Please quote the FCC regulations limiting AM BCB to 5 kHz.

Peter

On Mon, 14 Jul 2003 16:22:27 -0400, " Uncle Peter"
wrote:


"opcom" wrote in message
...
Not studio quality.
Studio quality AM is +/- 5KHz.


Please quote the FCC regulations limiting AM BCB to 5 kHz.

Not. Sharp rolloff at approximately 10KHz.

Uncle Peter wrote:
"opcom" wrote in message
...
Not studio quality.
Studio quality AM is +/- 5KHz.

Please quote the FCC regulations limiting AM BCB to 5 kHz.

Sadly, with all the NRSC crap in place, it's close to that. Didn't used to
be a decade ago. It's going to get worse with the new regulations that are
coming with IBOC too. AM quality is just going to hell and it's the result
of the listeners, the FCC, the station owners, and the radio manufacturers
all not giving a damn.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

I made no reference to FCC regulations concerning what is or is not studio quality.


Uncle Peter wrote:

"opcom" wrote in message
...
Not studio quality.
Studio quality AM is +/- 5KHz.

Please quote the FCC regulations limiting AM BCB to 5 kHz.

Peter

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


Please quote the FCC regulations limiting AM BCB to 5 kHz.

I haven't seen a BCB Station license in decades, but every other
commercial station license I've seen had the bandwidth indicated
on the license.

Is that also true with AM Broadcasting, and if true, what
bandwidth is allowed?

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

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.

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

Why so wide?

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.)

"WB3FUP (Mike Hall)" wrote:

And voice communications requires studio quality
audio WHY

Heh heh, do we need to rub it in? (Yes, and in one word
the answer is: ego.)

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

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