wrote:
I found this web page while looking for a nifty audio filter I found
last year.
At the very least it gives food for thought.

http://www.radiointel.com/phil/phils_radio_tuning_tricks.pdf

Terry

Eh, the author confuses DSB and AM. I wouldn't put much faith in
his/her analysis.

) writes:
wrote:
I found this web page while looking for a nifty audio filter I found
last year.
At the very least it gives food for thought.

http://www.radiointel.com/phil/phils_radio_tuning_tricks.pdf

Terry

Eh, the author confuses DSB and AM. I wouldn't put much faith in
his/her analysis.

Huh? IN what way?

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.

Some of the problem with AM reception discussion is that it was defined in
a certain set of terms, for decades and then even for beginners up
till recent times (and maybe even today). So they'd define AM as
a signal that is amplitude modulated, and that sets things up for
the vision that the carrier amplitude goes up and down. Then when
SSB became commonplace, instead of going back from the beginning
and redefining it all, a separate set of definitions gets tacked on.

This leaves people thinking they AM and SSB are two different things,
when they are basically the same.

Then when discussion of "low distortion AM detectors" comes along, it
isn't even clear what people are talking about. Because one is not
using a certain type of detector for AM (ie 2 sidebands with a carrier),
and a different type for SSB. The talk of "Amplitude Modulation" invokes
a vision of a detector that is following the voltage variations of the
signal. But that's not the case at all.

The carrier mixes with the sideband in the "envelope detector" and that
beating is what brings the modulation back down to "baseband". It's just
not a good mixer.

Listen to an SSB signal without a carrier or BFO. That's the sound of the
envelope varying according to the modulating signal, and there's no way
to make sense of it without a carrier. No differing loads on the dioded
detector, no precision half wave detector (with the diode in a feedback
loop), no forward biasing of the diode, can ever make up for the lack of
carrier.

The carrier of an AM signal is needed to beat with the sidebands and
get it back to audio. If the carrier fades in comparison with the
sidebands, you start hearing things like that SSB with an "envelope
detector", because the carrier is no longer strong enough to mix the
sidebands down to audio, and the "envelope detector" is actually
following the envelope of the signal.

The basic concept of demodulation is no different whether the signal
is AM (with carrier), DSB (with no carrier) or SSB (with no carrier). They
all need the carrier, or a locally synthesized equivalent, to beat the
sideband(s) down to audio.

If things were spoken of that way from the beginning, then there'd be less
of a leap to the "synchronous detector". No only would a universal set
of concepts be applied to all modes, but the point of a synchronous
modulator would become clear.

A single diode is a lousy mixer. On the other hand, since the carrier
of an AM signal comes in with the sidebands, there's no reason for
having a second and isolated input for that carrier.

But, long ago, people would mess with "exalted carrier reception", which
would be the first step up from those "envelope detectors". They'd turn
on the Q-multiplier, which had a narrow peak but a wide skirt, and that
would boost the incoming carrier in reference to the sidebands, so
there was a stronger carrier feeding into the "mixer".

It seems that only when SSB came along, and there were design reasons
to go to better mixers for the demodulation, that two input mixers started
being used, commonly called "product detectors". There were design reasons
for going to those, but the basic concept of a locally generated carrier
did not require anything more than the single diode "envelope detector".
Indeed, the concept had been there back in the days of regen receivers,
and every superhet that could be used for CW had a BFO that would feed
into the "envelope detector", to give to provide a beat with the incoming
signal. I should point out that when the synchronous detector was described
in CQ magazine in the late fifties, the actual mixers were single diodes.

But once you had product detectors, that opened things up. The notion of
boosting the incoming carrier for better mixing action became more clear.
I've said before, there was an article in QST about an advanced receiver
in the fifties, and it had two parallel IF chains. One wide for voice,
the other narrow for CW. But, it also allowed the output of the narrow
chain to feed the product detector, and there was the "quasi-synchronous
detector" before anyone came up with the name.

For AM (with carrier), you had two choices. You could strip off
the extra sideband and carrier, then the incoming signal was the
same as an SSB signal, and then demodulate it as an SSB signal. This
saw a lot of useage in the sixties, when SSB only ham rigs hit
the market, and yet AM was still common. People needed a means of
demodulating the AM signals, and that worked. While I think it
got discussed in the fifties as a better means of AM demodulation,
nobody in the sixties was talking that way. It was just a means of
demodulating AM signals when there was no means of doing so. (Not
only did the SSB-only receivers have narrow IF filters, but often
there was no way of turning off the BFO, and the product detectors
were a type of mixer that required having that second signal
at the second input; without it, you'd get little or no output
even with an AM signal that brought it's own carrier.)

But if you didn't want to do that, you had to deal with getting
the "locally generated carrier" in the right place. Not just
so it wouldn't beat against the incoming carrier (when it
was strong enough) but if it wasn't placed in the right place,
the sidebands would not be translated back to audio in the same
places. (So if you sent a 1KHz tone, and the "locally generated
carrier" was not right in the middle between those sidebands, one
sideband would translate down so that 1KHz tone was 1010Hz while
the other would translated down to 990Hz, which would obviously
clash with each other.)

That's what the "synchronous" bit is about. It's about putting
the same sort of BFO that you'd use with SSB (which would feed
the same sort of product detector used for SSB), with the addition
of circuitry to synchronize the BFO with the carrier of the incoming
AM Signal.

If the discussion had started with the AM detector as a mixer, then
there'd be little magic about "synchronous detectors". The whole
process is simply about getting the "carrier" strong in reference
to the sidebands, so good mixing happens in the detector. The
"synchronous" bit is only a secondary thing, a need because
you want the locally generated carrier in the right place.

There have always been various means of getting better mixing
action at the demodulator. But the important thing has always
been about doing that.

Michael

Michael Black wrote:
) writes:
wrote:
I found this web page while looking for a nifty audio filter I found
last year.
At the very least it gives food for thought.

http://www.radiointel.com/phil/phils_radio_tuning_tricks.pdf

Terry

Eh, the author confuses DSB and AM. I wouldn't put much faith in
his/her analysis.

Huh? IN what way?

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.

DSB never has a carrier. There is no such thing as DSB and DSB without
a carrier, just DSB.

Think of a mixer. If the signal are zero mean, you get DSB. If there is
a DC offset on the modulating signal, you get AM.


Some of the problem with AM reception discussion is that it was defined in
a certain set of terms, for decades and then even for beginners up
till recent times (and maybe even today). So they'd define AM as
a signal that is amplitude modulated, and that sets things up for
the vision that the carrier amplitude goes up and down. Then when
SSB became commonplace, instead of going back from the beginning
and redefining it all, a separate set of definitions gets tacked on.

This leaves people thinking they AM and SSB are two different things,
when they are basically the same.

No, AM and SSB are different.


Then when discussion of "low distortion AM detectors" comes along, it
isn't even clear what people are talking about. Because one is not
using a certain type of detector for AM (ie 2 sidebands with a carrier),
and a different type for SSB. The talk of "Amplitude Modulation" invokes
a vision of a detector that is following the voltage variations of the
signal. But that's not the case at all.

The carrier mixes with the sideband in the "envelope detector" and that
beating is what brings the modulation back down to "baseband". It's just
not a good mixer.

Listen to an SSB signal without a carrier or BFO. That's the sound of the
envelope varying according to the modulating signal, and there's no way
to make sense of it without a carrier. No differing loads on the dioded
detector, no precision half wave detector (with the diode in a feedback
loop), no forward biasing of the diode, can ever make up for the lack of
carrier.

And when did I comment about SSB?


The carrier of an AM signal is needed to beat with the sidebands and
get it back to audio. If the carrier fades in comparison with the
sidebands, you start hearing things like that SSB with an "envelope
detector", because the carrier is no longer strong enough to mix the
sidebands down to audio, and the "envelope detector" is actually
following the envelope of the signal.

The basic concept of demodulation is no different whether the signal
is AM (with carrier), DSB (with no carrier) or SSB (with no carrier). They
all need the carrier, or a locally synthesized equivalent, to beat the
sideband(s) down to audio.

If things were spoken of that way from the beginning, then there'd be less
of a leap to the "synchronous detector". No only would a universal set
of concepts be applied to all modes, but the point of a synchronous
modulator would become clear.

A single diode is a lousy mixer. On the other hand, since the carrier
of an AM signal comes in with the sidebands, there's no reason for
having a second and isolated input for that carrier.

But, long ago, people would mess with "exalted carrier reception", which
would be the first step up from those "envelope detectors". They'd turn
on the Q-multiplier, which had a narrow peak but a wide skirt, and that
would boost the incoming carrier in reference to the sidebands, so
there was a stronger carrier feeding into the "mixer".

It seems that only when SSB came along, and there were design reasons
to go to better mixers for the demodulation, that two input mixers started
being used, commonly called "product detectors". There were design reasons
for going to those, but the basic concept of a locally generated carrier
did not require anything more than the single diode "envelope detector".
Indeed, the concept had been there back in the days of regen receivers,
and every superhet that could be used for CW had a BFO that would feed
into the "envelope detector", to give to provide a beat with the incoming
signal. I should point out that when the synchronous detector was described
in CQ magazine in the late fifties, the actual mixers were single diodes.

But once you had product detectors, that opened things up. The notion of
boosting the incoming carrier for better mixing action became more clear.
I've said before, there was an article in QST about an advanced receiver
in the fifties, and it had two parallel IF chains. One wide for voice,
the other narrow for CW. But, it also allowed the output of the narrow
chain to feed the product detector, and there was the "quasi-synchronous
detector" before anyone came up with the name.

For AM (with carrier), you had two choices. You could strip off
the extra sideband and carrier, then the incoming signal was the
same as an SSB signal, and then demodulate it as an SSB signal. This
saw a lot of useage in the sixties, when SSB only ham rigs hit
the market, and yet AM was still common. People needed a means of
demodulating the AM signals, and that worked. While I think it
got discussed in the fifties as a better means of AM demodulation,
nobody in the sixties was talking that way. It was just a means of
demodulating AM signals when there was no means of doing so. (Not
only did the SSB-only receivers have narrow IF filters, but often
there was no way of turning off the BFO, and the product detectors
were a type of mixer that required having that second signal
at the second input; without it, you'd get little or no output
even with an AM signal that brought it's own carrier.)

But if you didn't want to do that, you had to deal with getting
the "locally generated carrier" in the right place. Not just
so it wouldn't beat against the incoming carrier (when it
was strong enough) but if it wasn't placed in the right place,
the sidebands would not be translated back to audio in the same
places. (So if you sent a 1KHz tone, and the "locally generated
carrier" was not right in the middle between those sidebands, one
sideband would translate down so that 1KHz tone was 1010Hz while
the other would translated down to 990Hz, which would obviously
clash with each other.)

That's what the "synchronous" bit is about. It's about putting
the same sort of BFO that you'd use with SSB (which would feed
the same sort of product detector used for SSB), with the addition
of circuitry to synchronize the BFO with the carrier of the incoming
AM Signal.

If the discussion had started with the AM detector as a mixer, then
there'd be little magic about "synchronous detectors". The whole
process is simply about getting the "carrier" strong in reference
to the sidebands, so good mixing happens in the detector. The
"synchronous" bit is only a secondary thing, a need because
you want the locally generated carrier in the right place.

There have always been various means of getting better mixing
action at the demodulator. But the important thing has always
been about doing that.

Michael

Christ all mighty, what is with the verbal diarrhea? You are trying to
analyze modulation by looking at demodulation. This is wrong thinking.
You analyze modulation by looking at modulators.

AM:
One mixer. Feed it a carrier and signal. The carrier is zero mean. The
signal has a DC bias sufficient that the signal always remains
positive. Congrats, you gave birth to AM.
DSB:
One mixer: Feed it zero mean carrier and signal. Out pops DSB.
SSB:
Slightly more complicated since it involves Hilbert transformers and
quadrature mixers. I can do an explanation, but it might take a
paragraph.

My original comment still stands. The author of the paper confused AM
and DSB.

Michael Black wrote:

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.
snip
Michael

Back in 1972 when I took my FFC 2nd and 1st class exams DSB was defined
as the sidebands with a supressed carrier. A signal with both sidebands
and the
carrier was simply AM with a BW disgnator. .Now that diffintion may
have slipped
over the years, but from my perspective AM means both sidebands, with a
carier
DSB means both sidebands without the carrier, and ISB means two
different
sidebands with no carrier. I only have received the later, ISB, a very
few times
mainly on ancient STL links.

It might be useful to check out what the ITU says these days about
"AM", both sidebands with carrier", and for this conversation, "DSB"
being both sidebands without the carrier.

Terry

wrote:
Michael Black wrote:

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.
snip
Michael

Back in 1972 when I took my FFC 2nd and 1st class exams DSB was defined
as the sidebands with a supressed carrier. A signal with both sidebands
and the
carrier was simply AM with a BW disgnator. .Now that diffintion may
have slipped
over the years, but from my perspective AM means both sidebands, with a
carier
DSB means both sidebands without the carrier, and ISB means two
different
sidebands with no carrier. I only have received the later, ISB, a very
few times
mainly on ancient STL links.

It might be useful to check out what the ITU says these days about
"AM", both sidebands with carrier", and for this conversation, "DSB"
being both sidebands without the carrier.

Terry

That high authority, Wikipedia, at http://en.wikipedia.org/wiki/DSB
says, "in telecommunications, double-sideband transmission - see also
double-sideband suppressed-carrier transmission (DSB-SC) and
double-sideband reduced carrier transmission (DSB-RC)".

That is supported by ATIS Telecom Glossary 2000 (ANSI approved) at
http://www.atis.org/tg2k/ : "DSB: Abbreviation for double sideband. See
double-sideband transmission." --- "double-sideband (DSB)
transmission: AM transmission in which both sidebands and the carrier
are transmitted." and "DSB-SC: Abbreviation for double-sideband
suppressed carrier. See double-sideband suppressed-carrier
transmission." --- "double-sideband suppressed-carrier (DSB-SC)
transmission: Transmission in which (a) frequencies produced by
amplitude modulation are symmetrically spaced above and below the
carrier frequency and (b) the carrier level is reduced to the lowest
practical level, ideally completely suppressed. Note: DSB-SC
transmission is a special case of double-sideband reduced carrier
transmission."

Accordingly, DSB=AM unmodified and AM is the essential first step for
its modified variants SSB, ISB, DSB-SC/DSB-RC.

Tom

Tom wrote:
wrote:
Michael Black wrote:

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.
snip
Michael

Back in 1972 when I took my FFC 2nd and 1st class exams DSB was defined
as the sidebands with a supressed carrier. A signal with both sidebands
and the
carrier was simply AM with a BW disgnator. .Now that diffintion may
have slipped
over the years, but from my perspective AM means both sidebands, with a
carier
DSB means both sidebands without the carrier, and ISB means two
different
sidebands with no carrier. I only have received the later, ISB, a very
few times
mainly on ancient STL links.

It might be useful to check out what the ITU says these days about
"AM", both sidebands with carrier", and for this conversation, "DSB"
being both sidebands without the carrier.

Terry

That high authority, Wikipedia, at http://en.wikipedia.org/wiki/DSB
says, "in telecommunications, double-sideband transmission - see also
double-sideband suppressed-carrier transmission (DSB-SC) and
double-sideband reduced carrier transmission (DSB-RC)".

That is supported by ATIS Telecom Glossary 2000 (ANSI approved) at
http://www.atis.org/tg2k/ : "DSB: Abbreviation for double sideband. See
double-sideband transmission." --- "double-sideband (DSB)
transmission: AM transmission in which both sidebands and the carrier
are transmitted." and "DSB-SC: Abbreviation for double-sideband
suppressed carrier. See double-sideband suppressed-carrier
transmission." --- "double-sideband suppressed-carrier (DSB-SC)
transmission: Transmission in which (a) frequencies produced by
amplitude modulation are symmetrically spaced above and below the
carrier frequency and (b) the carrier level is reduced to the lowest
practical level, ideally completely suppressed. Note: DSB-SC
transmission is a special case of double-sideband reduced carrier
transmission."

Accordingly, DSB=AM unmodified and AM is the essential first step for
its modified variants SSB, ISB, DSB-SC/DSB-RC.

Tom

I guess that diffintions aren't static, er fixed.
Thanks for the clarification.

Terry

In article . com,
wrote:

Tom wrote:
wrote:
Michael Black wrote:

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about
the components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no
carrier", but technically one should specifically define that
there is no carrier.
Snip

Back in 1972 when I took my FFC 2nd and 1st class exams DSB was
defined as the sidebands with a supressed carrier. A signal with
both sidebands and the carrier was simply AM with a BW disgnator.
.Now that diffintion may have slipped over the years, but from my
perspective AM means both sidebands, with a carier DSB means both
sidebands without the carrier, and ISB means two different
sidebands with no carrier. I only have received the later, ISB, a
very few times mainly on ancient STL links.

It might be useful to check out what the ITU says these days
about "AM", both sidebands with carrier", and for this
conversation, "DSB" being both sidebands without the carrier.


That high authority, Wikipedia, at http://en.wikipedia.org/wiki/DSB
says, "in telecommunications, double-sideband transmission - see
also double-sideband suppressed-carrier transmission (DSB-SC) and
double-sideband reduced carrier transmission (DSB-RC)".

That is supported by ATIS Telecom Glossary 2000 (ANSI approved) at
http://www.atis.org/tg2k/ : "DSB: Abbreviation for double sideband.
See double-sideband transmission." --- "double-sideband (DSB)
transmission: AM transmission in which both sidebands and the
carrier are transmitted." and "DSB-SC: Abbreviation for
double-sideband suppressed carrier. See double-sideband
suppressed-carrier transmission." --- "double-sideband
suppressed-carrier (DSB-SC) transmission: Transmission in which (a)
frequencies produced by amplitude modulation are symmetrically
spaced above and below the carrier frequency and (b) the carrier
level is reduced to the lowest practical level, ideally completely
suppressed. Note: DSB-SC transmission is a special case of
double-sideband reduced carrier transmission."

Accordingly, DSB=AM unmodified and AM is the essential first step
for its modified variants SSB, ISB, DSB-SC/DSB-RC.


I guess that diffintions aren't static, er fixed. Thanks for the
clarification.

Looks to me that acronym DSB does not define the carrier condition.
That's why the dash and more letters.

--
Telamon
Ventura, California

On Sun, 03 Dec 2006 01:10:52 GMT, Telamon
wrote:


clarification.

Looks to me that acronym DSB does not define the carrier condition.
That's why the dash and more letters.
FCC EMISSION DESIGNATORS
Detailed List
Last Rev. 1998


WARC-79, the World Administrative Radio Conference that rewrote many
of the world's radio regulations, adopted a new system of emission
classification. The traditional A (Amplitude), F (Frequency), and P
(Pulse) was intuitive, but limited and clumsy when dealing with new
modes.

The world's radio bodies, including the FCC, gradually phased in the
new system until today it completely replaces the old one.

The formula for the new designations, loosely from ITU radio
regulations 264 through 273, and Appendix 6, Part A, is:

[BBBB]MNI[DM],

where

[] means optional when writing emission specs.


[BBBB] = Necessary Bandwidth (shown in FCC records, but is often
omitted elsewhere)

Uses a letter and three numbers. The letter goes where the decimal
point should be placed, and denotes a magnitude:

H Hz
K kHz
M MHz
G GHz

Some common bandwidths a

400 Hz 400H
2.4 kHz 2K40
12.5 kHz 12K5
6 MHz 6M00



M = Modulation Type

N None
A AM (Amplitude Modulation), double sideband, full carrier
H AM, single sideband, full carrier
R AM, single sideband, reduced or controlled carrier
J AM, single sideband, suppressed carrier
B AM, independent sidebands
C AM, vestigial sideband (commonly analog TV)

F Angle-modulated, straight FM
G Angle-modulated, phase modulation (common; sounds like FM)

D Carrier is amplitude and angle modulated

P Pulse, no modulation
K Pulse, amplitude modulation (PAM, PSM)
L Pulse, width modulation (PWM)
M Pulse, phase or position modulation (PPM)
Q Pulse, carrier also angle-modulated during pulse
W Pulse, two or more modes used

X All cases not covered above


N = Nature of modulating signal

0 None
1 Digital, on-off or quantized, no modulation
2 Digital, with modulation
3 Single analog channel
7 Two or more digital channels
8 Two or more analog channels
9 Composite, one or more digital channel, one or more analog

X All cases not covered above


I = Information type

N None
A Aural telegraphy, for people (Morse code)
B Telegraphy for machine copy (RTTY, fast Morse)
C Analog fax
D Data, telemetry, telecommand
E Telephony, voice, sound broadcasting
F Video, television
W Combinations of the above

X All cases not covered above


[DM] = additional details, not used by FCC, optional elsewhere

D = Detail


RTTY/modems:

A Two condition code, differing numbers or durations (Morse)
B Two condition code, same number and duration, no error check
C Two condition code, same num & dur, error check
D Four condition code, 1 or more bits per condition
E Multi condition code, 1 or more bits per condition
F Multi condition code, conditions may combine

Audio:

G Broadcast quality (mono)
H Broadcast quality (stereo/multichannel)
J Commercial quality
K Commercial quality, analog freq inversion or band scrambling
L Commercial quality, FM pilot tone (i.e. Lincomprex)

Video:

M Monochrome
N Color


W Combination

X All cases not covered above



M = Multiplex type

N None
C Code division
F Frequency division
T Time division
W Combination of above

X All other types



-----------------------------------------------------------------------


Converting Between Old & New Systems


-----------------------------------------------------------------------


USE OLD NEW

Pure carrier A0,F0 N0N
Morse telegraphy (by ear) A1 A1A
Modulated CW Morse A2 A2A
AM voice A3 A3E
SSB, suppressed carrier A3J J3E
SSB, reduced carrier A3R R3E
SSB, full carrier A3H H3E
Television A5 C3F

RTTY (F.S.K.) F1 F1B
RTTY (A.F.S.K.) F2 F2B
FM voice (Narrowband) F3 F3E, 20K0F3E


Packet Data/Teleprinters
with Audio Sub-Carrier 20F2 20K0F2B

Data with Audio Sub-carrier 3F2 3K00F2D
6F2 6K00F2D
20F2 20K0F2D

Analog Voice 20F3 20K0F3E

Digital Voice 20F3Y 20K0F1E

Digital Facsimile without
Audio Sub-Carrier 20F4 20K0F1C

Digital Facsimile with
Audio Sub-Carrier 20F4 20K0F2C

Analog Facsimile 20F4 20K0F3C

Composite of Digital &
Analog Information 3F9 3K00F9W
6F9 6K00F9W
20F9 20K0F9W

Packet Data/Teleprinters
without Audio Sub-Carrier 20F9Y 20K0F1B

Digital Data 20F9Y 20K0F1D



LAND MOBILE EMISSIONS MICROWAVE EMISSIONS
old new old new old new
A0 N0N P0 P0N F9 F8W (If bw is less than
A1 A1A P9 P0N 50 convert to F2D)
A3 A3E A2J J2B F9Y F7W (If bw is less than
A3J J3E A3H H3E 50 convert to F2D)
A7J J8W A9J J9W F3 F3E
A9 A9W P1 P1D A9Y A7W
A9Y A1D F2Y F2D A5 A3F
F0 N0N A0H H0N A9 A8W
F1 F1B A7 A8D A5C C3F
F2 F2D F7 F8D F2 F2D
F3 F3E F5 F3F
F3Y F1E
F4 F3C
F9 F9W
F9Y F1D
A2H H2D
A2 A2D


----------------------------------------------------------------------

And here is the relevant section of FCC rules:

----------------------------------------------------------------------




From General Docket No. 80-739

Section 2.201 Emission, modulation, and transmission characteristics.


The following system of designating emission, modulation, and
transmission characteristics shall be employed.

(a) Emissions are designated according to their classification and
their necessary bandwidth.

(b) A minimum of three symbols are used to describe the basic
characteristics of radio waves. Emissions are classified and
symbolized according to the following characteristics:

(1) First symbol - type of modulation of the main carrier;

(2) Second Symbol - nature of signal(s) modulating the main
carrier;

(3) Third symbol - type of information to be transmitted.

NOTE: A fourth and fifth symbol are provided for additional
information and are shown in Appendix 6, Part A of the ITU Radio
Regulations. Use of the fourth and fifth symbol is optional.
Therefore, the symbols may be used as described in Appendix 6,
but are not required by the Commission.

(c) First Symbol - types of modulation of the main carrier:

(1) Emission of an unmodulated carrier N

(2) Emission in which the main carrier is amplitude-
modulated (including cases where sub-carriers are angle
modulated):
- Double-sideband A
- Single-sideband, full carrier H
- Single-sideband, reduced or variable level carrier R
- Single-sideband, suppressed carrier J
- Independent sidebands B
- Vestigial sideband C

(3) Emission in which the main carrier is angle-modulated:
- Frequency modulation F
- Phase modulation G

NOTE: Whenever frequency modulation "F" is indicated,
Phase modulation "G" is also acceptable.

(4) Emission in which the main carrier is amplitude and
angle-modulated either simultaneously or in a pre-
established sequence D

(5) Emission of pulses:*
- Sequence of unmodulated pulses P
- A sequence of pulses:
- Modulated in amplitude K
- Modulated in width/duration L
- Modulated in position/phase M
- In which the carrier is angle-modulated during the
period of the pulse Q
- Which is a combination of the foregoing or is
produced by other means V

(6) Cases not covered above, in which an emission consists
of the main carrier modulated, either simultaneously or
in a pre-established sequence, a combination of two or
more of the following modes: amplitude, angle, pulse W

(7) Cases not otherwise covered X

*Emissions where the main carrier is directly modulated by a
signal which has been coded into quantizied form (e.g.,
pulse code modulation) should be designated under (2) or
(3).

(d) Second Symbol- nature of signal(s) modulating the main
carrier:

(1) No modulating signal 0

(2) A single channel containing quantized or digital
information without the use of a modulating sub-
carrier, excluding time-division multiplex 1

(3) A single channel containing quantized or digital
information with the use of a modulating sub-carrier,
excluding time-division multiplex 2

(4) A single channel containing analogue information 3

(5) Two or more channels containing quantized or digital
information 7

(6) Two or more channels containing analogue information 8

(7) Composite system with one or more channels containing
quantized or digital information, to-gether with one or
more channels containing analogue information 9

(8) Cases not otherwise covered X

(e) Third Symbol - type of information to be transmitted:

(1) No information transmitted N

(2) Telegraphy - for aural reception A

(3) Telegraphy - for automatic reception B

(4) Facsimile C

(5) Data transmission, telemetry, telecommand D

(6) Telephony (including sound broadcasting) E

(7) Television (video) F

(8) Combination of the above W

(9) Cases not otherwise covered X

(f) Type B emission: As an exception to the above principles,
damped waves are symbolized in the Commission's rules and
regulations as type B emission. The use of type B emissions
is forbidden.

(g) Whenever the full designation of an emission is necessary,
the symbol for that emission, as given above, shall be
preceded by the necessary bandwidth of the emission as
indicated in Section 2.202 (b) (1).


Section 2.202 Bandwidths.

(b) Necessary bandwidths.

(1) The necessary bandwidth shall be expressed by three
numerals and one letter. The letter occupies the
position of the decimal point and represents the unit
of bandwidth. The first character shall be neither
zero nor K, M or G.

-

-end-

) writes:
Michael Black wrote:

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.
snip
Michael

Back in 1972 when I took my FFC 2nd and 1st class exams DSB was defined
as the sidebands with a supressed carrier. A signal with both sidebands
and the
carrier was simply AM with a BW disgnator. .Now that diffintion may
have slipped
over the years, but from my perspective AM means both sidebands, with a
carier
DSB means both sidebands without the carrier, and ISB means two
different
sidebands with no carrier. I only have received the later, ISB, a very
few times
mainly on ancient STL links.

It might be useful to check out what the ITU says these days about
"AM", both sidebands with carrier", and for this conversation, "DSB"
being both sidebands without the carrier.

Terry

Are you arguing semantics, or understanding?

The post I replied to was almost outraged by that PDF's useage of "DSB".
I couldn't figure out whether he was just fussing over words (and thus
why was he so outraged?), or really does believe that DSB is not AM.

Because people have become sloppy about the words, some of all
these conversations about "better AM detectors" is limited. Because
people are searching for something that really isn't all that different
from what's already available. That PDF talks in terms of how
synchronous detectors get too much hype, yet the author turns around
and uses everything a "synchronous detector" has except the actual
synchronization. But the synchronization isn't actually what provides
the potentially improved reception, it's just a means of compensating
for some side effects.

I never got around to replying, but a few months ago someone started
a thread here where he stated something like "So I gather the carrier
is more likely to fade when selective fading is happening". I haven't
a clue whether the carrier is more likely to fade than the sidebands, but
once the carrier fades in relationship to the sidebands you're going to
start having reception problems, and once the carrier completely fades
you won't be able to recover the modulation. The carrier is the key
part to demodulation. But a more universal understanding of "amplitude
modulation" would show right away that you can't demodulate a DSB
signal unless a carrier is sent along, or generated locally at the receiver
end, and selective fading can mean that a DSBc signal sent from the
transmitter may be a DSBsc (Double SIdeband suppressed carrier) by the
time it reaches the receiver.

So in this sort of talk, you'd better start being specific about what
you are talking about. Since DSB (with or without a carrier) and
SSB (with or without a carrier) are "AM", then you really need to
stop using "AM" to only mean DSBc.

Hence DSB in the PDF is more descriptive than AM. Is he confused?
I don't think so. In his opening paragraph he says "Note: DSB (Double
Sideband full-carrier) and SSB (single sideband suppressed carrier) are
both amplitude modulation". He defines the term as he is about to
use them, so there is no confusion. He needs to use the DSB rather
than a more generic "AM" because he is very much thinking in terms
of two sidebands (even if he turns around and removes one). The
fact that there are two sidebands rather than one may be more significant
than whether or not there is a carrier.

Since he defined his terms to begin with, any subsequent useage of
"DSB" is taken care of. But, again, even if that was not the case,
his useage is fine, because whether or not a carrier is sent is
irrelevant to his discussion. It's easy to get a locally generated
"carrier", and if it's just one sideband it's done all the time, with
a bit of mistuning. But with two sidebands, it's far harder. Hence
you can either determine where the locally generated carrier needs to
be from the the redundant sidebands, or strip off one sideband so it
becomes SSB and placing the carrier becomes much easier.

Maybe he should have gone with DSBc to show that he is talking about
a DSB signal with carrier, but that is hardly a confusion of AM and DSB.

As for common useage of so many of these terms, nobody had to specify
how many sidebands and whether a carrier went with it until they
started to use a subset of that stuff. Look in early articles about
SSB and it was pretty common for them to be most specific, ie SSBsc (SSB
suppressed carrier). It's only later that it simply became SSB. Nobody
really thought of sending DSB without a carrier until SSB came along,
and there too it was not uncommon to see it referred to as DSBsc.

Michael

Michael Black wrote:
) writes:
Michael Black wrote:

I glanced at it and maybe missed something, but DSB is AM. And
he certainly says it at the outset, and when he's talking about the
components he's talking about 2 sidebands and a carrier.

Now, "DSB" often has fallen into the meaning of "DSB with no carrier",
but technically one should specifically define that there is no carrier.
snip
Michael

Back in 1972 when I took my FFC 2nd and 1st class exams DSB was defined
as the sidebands with a supressed carrier. A signal with both sidebands
and the
carrier was simply AM with a BW disgnator. .Now that diffintion may
have slipped
over the years, but from my perspective AM means both sidebands, with a
carier
DSB means both sidebands without the carrier, and ISB means two
different
sidebands with no carrier. I only have received the later, ISB, a very
few times
mainly on ancient STL links.

It might be useful to check out what the ITU says these days about
"AM", both sidebands with carrier", and for this conversation, "DSB"
being both sidebands without the carrier.

Terry

Are you arguing semantics, or understanding?

It is not sematics, but generally agreed upon definitions.

The post I replied to was almost outraged by that PDF's useage of "DSB".
I couldn't figure out whether he was just fussing over words (and thus
why was he so outraged?), or really does believe that DSB is not AM.

Because people have become sloppy about the words, some of all
these conversations about "better AM detectors" is limited. Because
people are searching for something that really isn't all that different
from what's already available. That PDF talks in terms of how
synchronous detectors get too much hype, yet the author turns around
and uses everything a "synchronous detector" has except the actual
synchronization. But the synchronization isn't actually what provides
the potentially improved reception, it's just a means of compensating
for some side effects.

I never got around to replying, but a few months ago someone started
a thread here where he stated something like "So I gather the carrier
is more likely to fade when selective fading is happening". I haven't
a clue whether the carrier is more likely to fade than the sidebands, but
once the carrier fades in relationship to the sidebands you're going to
start having reception problems, and once the carrier completely fades
you won't be able to recover the modulation. The carrier is the key
part to demodulation. But a more universal understanding of "amplitude
modulation" would show right away that you can't demodulate a DSB
signal unless a carrier is sent along, or generated locally at the receiver
end, and selective fading can mean that a DSBc signal sent from the
transmitter may be a DSBsc (Double SIdeband suppressed carrier) by the
time it reaches the receiver.

So in this sort of talk, you'd better start being specific about what
you are talking about. Since DSB (with or without a carrier) and
SSB (with or without a carrier) are "AM", then you really need to
stop using "AM" to only mean DSBc.

Hence DSB in the PDF is more descriptive than AM. Is he confused?
I don't think so. In his opening paragraph he says "Note: DSB (Double
Sideband full-carrier) and SSB (single sideband suppressed carrier) are
both amplitude modulation". He defines the term as he is about to
use them, so there is no confusion. He needs to use the DSB rather
than a more generic "AM" because he is very much thinking in terms
of two sidebands (even if he turns around and removes one). The
fact that there are two sidebands rather than one may be more significant
than whether or not there is a carrier.

Since he defined his terms to begin with, any subsequent useage of
"DSB" is taken care of. But, again, even if that was not the case,
his useage is fine, because whether or not a carrier is sent is
irrelevant to his discussion. It's easy to get a locally generated
"carrier", and if it's just one sideband it's done all the time, with
a bit of mistuning. But with two sidebands, it's far harder. Hence
you can either determine where the locally generated carrier needs to
be from the the redundant sidebands, or strip off one sideband so it
becomes SSB and placing the carrier becomes much easier.

Maybe he should have gone with DSBc to show that he is talking about
a DSB signal with carrier, but that is hardly a confusion of AM and DSB.

As for common useage of so many of these terms, nobody had to specify
how many sidebands and whether a carrier went with it until they
started to use a subset of that stuff. Look in early articles about
SSB and it was pretty common for them to be most specific, ie SSBsc (SSB
suppressed carrier). It's only later that it simply became SSB. Nobody
really thought of sending DSB without a carrier until SSB came along,
and there too it was not uncommon to see it referred to as DSBsc.

I just don't buy the argument that nobody thought about DSB. DSB is
naturally generated from a mixer if the audio signal is zero mean.
[Again, it is best to talk about modulation schemes by discussion
modulators.] Remember, AM exists because the demod is cheaper, not
because it is any easier to generate that say DSB. AM and DSB use the
same hardware.

Michael

To get to the meat of the problem, the only utility in any of these
demod schemes is if you can narrow band the signal. That is, just
because you can build a demodulator that can use both sidebands without
need of the carrier, it doesn't mean the quality of the signal will be
any better. Wider bandwidth signals are more prone to atmospheric
effects, i.e. fading. Thus if you are going to do synchronous
detection, you need to receive one side band, period.