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http://gullfoss2.fcc.gov/prod/ecfs/retrieve.cgi?native_or_pdf=pdf&id_document=6516213125
Before the
Federal Communications Commission
Washington, D.C. 20554
In the Matter of )
Amendment of Part 97 of the Commissions Rules ) WT Docket No. 04-140
Governing the Amateur Radio Services )
TO: The Commission
Comments of Donald B. Chester
THIS COMMENTER
1. These are comments of Donald B. Chester, a licensed amateur operator
since 1959 and
Amateur Extra Class licensee since 1963, with amateur call sign K4KYV. This
commenter is
presently active on the 160, 80, 40 and 10 metre amateur bands with primary
interest in operating
voice and CW modes using mostly homebuilt equipment.
INTRODUCTION
2. I agree with the concept of the ARRL proposal regarding re-farming the
HF bands, that
the phone segments of the 80/75m and 40m amateur bands should be expanded.
In recent years I
have increasingly noticed a dearth of activity, except during certain
contest periods, throughout
the CW/RTTY/data segment of the 3.5-4.0 mHz band, even under optimum
wintertime
conditions on weekends during hours of darkness, when this band is most
heavily occupied.
During these same time periods the voice segment is often congested to the
point that it is of
limited use for reliable communication. The proposed changes for the 80/75m
band would grant
General class licensees only 50 kilohertz of additional voice spectrum,
while Advanced and Extra
class licensees would be granted a mere 25 additional kilohertz. For this
reason I feel that the
proposed changes do not go nearly far enough. The discussion that follows
will be limited to the
3.5-4.0 mHz band, where the allocation of emission modes is most clearly
disproportionate.
AVAILABLE COMMUNICATION CHANNELS UNDER PRESENT RULES
3. The present rules allow for voice and other wideband emissions in the
segment between
3.75 and 4.0 mHz, while CW is allowed throughout the entire 3.5-4.0 mHz
allocation. RTTY and
data modes are allowed only in the segment reserved for narrowband modes. In
actual practice,
CW is rarely used in the 3.75-4.0 mHz voice segment; therefore, CW operation
outside the
CW/RTTY/data segment will not be considered in the following discussion.
4. CW, RTTY and data emissions are capable of operating at very narrow
bandwidths,
sometimes less than 100 Hz, but due to equipment limitations and current
amateur practice, let us
assume a communications channel using these modes to have a nominal
bandwidth of 500 Hz.
This is a generous allowance, considering the frequency stability and
selectivity available to
amateurs today using modern equipment; therefore 500 Hz spacing would allow
narrowband
modes more than sufficient margin to operate without mutual interference.
5. Voice and image transmissions that normally operate in the 3.75-4.0 mHz
segment may
occupy different bandwidths depending on the particular modes of emission
used. Single
sideband voice and slow-scan television may occupy less than three
kilohertz, while double
sideband voice and narrowband FM modes may occupy seven kilohertz or more.
For the sake of
discussion, let us assume nominal bandwidths of 3.0 kHz for SSB and SSTV,
and 6.0 kHz for
DSB and NBFM, which represent the minimum practical bandwidths that would
allow for good
intelligibility using these modes following present day amateur practice
using equipment
currently available.
6. During periods of heavy band occupancy, approximately three voice
contacts will
typically be heard using double-sideband voice, while the rest will be using
SSB voice and slowscan
TV. Under the present rules, with a total of 250 kilohertz of spectrum where
voice
transmission is permitted, this calculates to eighty-three 3.0 kHz voice
channels with no
overlapping of signals. If three channels are occupied with double sideband
or NBFM
communication at 6.0 kHz bandwidth each, that would leave 77 channels
available for
SSB/SSTV, or a total of 80 voice channels free of interference with no
overlapping of signals. In
actual practice, a considerable amount of signal overlap during congested
conditions is to be
expected. Interference is a fact of life in amateur radio communications and
most amateurs
operate with this expectation in mind. Therefore, in reality, the 250 kHz
voice segment can
accommodate considerably more than 80 voice stations transmitting
simultaneously using all the
various legal modes. However, for the sake of this discussion, let us
consider the total number of
channels that would be available with no signal overlap and use the more
conservative figure of
80 stations.
7. The present rules provide 250 kilohertz of spectrum allocated exclusively
for CW, RTTY
and data modes. If the nominal channel bandwidth is assumed to be 500 Hertz,
this would allow
500 transmitters to operate simultaneously with no signal overlap or mutual
interference. Earlier
in the history of amateur radio, CW stations often required more than 500 Hz
bandwidth due to
frequency instability of transmitters and receivers and inadequate receiver
selectivity. However,
with the present generation of equipment available to amateur operators,
nearly perfect frequency
stability can be expected, and optimum selectivity is available with most
receivers. Using
modern equipment, amateurs can comfortably operate CW/RTTY/data with less
bandwidth than
500 Hz, and successful communication is possible with substantial signal
overlap as expected
with routine amateur communication, just as in the case of voice
transmission. Nevertheless,
using the more conservative figure of 500 kilohertz per signal and no
overlap, we can safely
estimate that under the present rules, 500 communication channels are
available for CW and other
narrow-band modes.
8. Comparing mode allocations under the present rules, we see that 500
interference-free
communication channels are available for CW/RTTY/data while only 80
interference-free
channels are available for voice, despite the fact that voice appears to be
more widely used on
3.5-4.0 mHz than CW/RTTY/data. On a typical winter evening (except during
certain contest
periods that occur a few weekends a year), fewer than a dozen CW and data
stations may be
heard throughout the 3.5-3.75 segment while the voice bands remain heavily
congested to the
point than many signals are unintelligible even with highly selective
receivers. Therefore, the
conclusion is inescapable that a disproportionate amount of spectrum is
presently allocated to the
CW/RTTY/data modes of emission within the 3.5-4.0 mHz amateur band.
AVAILABLE COMMUNICATION CHANNELS UNDER PROPOSED RULES
9. Under the changes originally proposed in the ARRL petition and proposed
by the
Commission in the current proceeding, relief from the disproportionate
allocations of
CW/RTTY/data emissions and voice emissions in the 3.5-4.0 mHz amateur band
would be
minimal at best. The proposed changes would reallocate a total of only 25
kHz from
CW/RTTY/data to voice. This would leave narrowband modes a total of 225
kilohertz of
spectrum and the wideband modes 275. With the same bandwidth figures as used
in the
discussion above, under the proposed changes, four-hundred-fifty 500-Hz
communication
channels would be available for CW/etc., while ninety-two 3.0 kHz channels
would be available
for voice. If we still assume that three of the voice contacts would be
using double-sideband or
narrowband FM, a total of 86 voice channels would be available with no
signal overlap.
CONCLUSION
10. In order to create a more equitable division of spectrum between users
of narrow-band
modes such as CW, RTTY and data, and wide-band modes such as image and
voice, I hereby
propose that the voice allocation be extended at least down to 3600 kHz.
This would leave 100
kHz of spectrum reserved for narrow-band modes while 400 kHz would be
available for
wideband modes. Using the same figures as in the above discussions,
two-hundred 500 Hertz
CW/RTTY/data channels and 133 three-kilohertz voice channels would be
available. Since the
additional interference-free spectrum might encourage more amateur stations
to use double sideband or NBFM voice, let us now assume five simultaneous
contacts using nominal 6.0 kHz
bandwidths. This would leave 123 channels at 3.0 kHz, allowing for a total
of 128 voice stations
to operate simultaneously without interference. Again, since some degree of
interference is
expected in amateur radio communications, these figures for the total number
of stations that
could transmit simultaneously are undoubtedly much more conservative than
what would be
expected in actual practice.
11. Please note that this discussion has been limited to the specific issue
of narrowband
versus wideband allocations within the 3.5-4.0 mHz band. I feel that the
situation on other
amateur bands, and how mode subbands may be be further subdivided by licence
class, are
separate issues beyond the scope intended for these comments.
Respectfully submitted,
Donald B. Chester
2116 Old Dover Road
Woodlawn, TN 37191
_________________________________________________________________
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