On 6/26/06, Steve Baron - KB3MM <SteveBaron@starlinx.com> wrote:
> How does the FCC define CW?
>
Having nothing better to do, I went to the FCC website to read up on
Part 97 and what they say about CW. The relevant sections are 97.3
which refer back to 2.201 and 2.202. Some excerpts are at the end.
Classical amateur CW might be 100HA1A, specifying 100 Hz bandwidth,
or simply A1A. The ARRL FCC Rule Book has some useful material, too.
It seems that the FCC is interested in the signal that shows up on the
air and not how it is generated. Fair enough. Everything we have
been talking about in this forum is A1A, I believe. Some generation
methods (like tones into a poor SSB rig) are worse than others. FCC
requires signal purity to observe good engineering practices, or words
to that effect, and that may rule out the KWM-1 technique nowadays.
The DSP method (e.g., Orion = TenTec content!) can be as perfect as
you're willing to pay for.
As the Rule Book (8th ed.) explains, it would be possible to narrow
the "100 Hz" DSB spectrum of an A1A signal by eliminating one sideband
(50 Hz) and suppressing the carrier. (However you make it, CW does
have a carrier and sidebands just like a voice signal.*) I wonder if
anyone has ever done it, and whether a half-width carrier-less CW (or
psk31?) signal would be decodeable after HF propagation. You'd need
really tight frequency and passband control.
73, Martin AA6E
*A carrier? What about between characters? Yes, mathematically the
carrier is still there -- even after you turn your rig off. Of
course, there are also very low freq sidebands that conveniently
cancel out the voltage... So your rig had better be very very linear
or it won't be safe to shut off the power! Don't lose sleep over it.
;-)
================================
97.3(c)
(1) CW. International Morse code telegraphy emissions having
designators with A, C, H, J or R as the first symbol; 1 as the second
symbol; A or B as the third symbol; and emissions J2A and J2B.
2.201
(c) 1st symbol
(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
...
--Vestigial sideband.............................................. C
...
(d) Second Symbol--nature of signal(s) modulating the main carrier:
...
(2) A single channel containing quantized or digital information 1
without the use of a modulating sub-carrier, excluding time-
division muliplex..................................................
(3) A single channel containing quantized or digital information 2
with the use of a modulating sub-carrier, excluding time-division
multiplex..........................................................
...
(e) Third Symbol--type of information to be transmitted:\2\
---------------------------------------------------------------------------
\2\ In this context the word ``information'' does not include
information of a constant, unvarying nature such as is provided by
standard frequency emissions, continuous wave and pulse radars, etc.
...
(2) Telegraphy--for aural reception................................ A
(3) Telegraphy--for automatic reception............................ B
(Also see 2.202 for the bandwidth designators which precede the
emission type designation.)
==========================================
--
martin.ewing@gmail.com
http://blog.aa6e.net
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