From: brian@ucsd.edu (Brian Kantor)
Newsgroups: rec.radio.amateur.policy
Subject: Minutes of the ARRL Committee on Amateur Radio Digital Communications
Date: 29 Jul 1992 16:02:00 GMT
Organization: Society for the Preservation of Obsolete Radio Communication Methods
NNTP-Posting-Host: ucsd.edu


                         Minutes of the

     ARRL Committee on Amateur Radio Digital Communications

                          June 13, 1992


The ARRL Committee on Amateur Radio Digital Communications met at
8:30 CDT on June 13, 1992 at the DFW Marriott Hotel, Dallas, TX. 
Ed Juge, W5TOO, Chairman presided and Vic Poor, W5SMM acted as
recording secretary.  In addition the following members were
present:  Tom Comstock, N5TC, Craig McCartney, WA8DRZ, Paul
Newland, AD71, and Dale Sinner, W6IWO.  Bob Poirier, KODJ, was
unable to attend.

Comstock reviewed the role of digital communications in past
emergencies including the Mexico City earthquake and hurricane
Hugo.

Poor reviewed the current state of the art of current and soon to
be introduced digital modes and their impact on h.f. spectrum
utilization.

The Committee as a whole reviewed the responses from the Digital
Survey conducted by QST and RTTY Journal.

A lengthy discussion followed on all the issues raised in
connection with the operation of unattended amateur h.f. digital
stations.  The recording secretary was directed to summarize these
discussions and the unanimously approved recommendations to the
ARRL Board in a separate report which is attached as a part of
these minutes.

Ed Juge, Chairman

Vic Poor, Recording Secretary


    Report and Recommendation to the ARRL Board of Directors

                             by the

     ARRL Committee on Amateur Radio Digital Communications

                          June 13, 1992


The ARRL Digital Committee has been asked by the ARRL Board of
study the issues related to use of automatic unattended control of
amateur stations operating digital modes in the h.f. spectrum and
to recommend what action the Board should take toward establishing
permanent rules for such operation, if any.

The Committee has carefully studied as many of the facts and
opinions as were available within the Committee's resources.  Data
bearing on the question included:

     The results of the ARRL Digit Survey;

     Frequency usage and allocations in the U.S. and in other
     countries;

     The current state of the art for amateur h.f. digital modes;

     Potential abuse of unattended operation such as illegal third
     party traffic;

     The various competing interests for h.f. spectrum,
     particularly between existing digital modes; and

     Amateur operating practices and traditions.

The ARRL Digital Survey

The members of the Committee carefully studied the tallies of
answers to the questions in the survey and read every written
comment submitted by the respondents.  The survey data showed that
majority of respondents favored permanent authorization of
unattended semi-automatic operation but limiting semi-automatic
operation to sub-bands, and a substantial majority did not approve
of unattended fully-automatic operation.

A wide range of opinions and proposals were made in the comments
attached to the survey, all of which were discussed and weighed by
the Committee.  The important issues raised are discussed below.

Frequency Usage and Allocations in the U.S. and other Countries

It is no secret that available space is very limited in the h.f.
spectrum.  Nowhere is that more evident than in the very popular 20
and 40 meter bands.  The two oldest modes of operation, voice and
c.w., have the lion's share of the spectrum in those bands since 
they were in heavy use before there were any digital modes.  The
digital modes have simply "squeezed in the crocks" between already
established modes of operation.  Since the digital modes have
become established they have expanded gradually, a little at a
time, primarily into space occupied by c.w. operation.  Frequencies
near the edges of digital mode operation continue to be shared by
both digital and non-digital modes.

Outside of the U.S., depending on the ITU region and the rules
adopted by various administrations, digital operation for any given
mode may not align with practice in this country and it does not
seem possible to establish a sub-band plan that could be
universally acceptable.  It is simply inevitable that any band
segment in the h.f. spectrum is going to be shared among differing
modes of operation.  This is not a new condition on the h.f. bands
and has been accommodated for decades.

Available Spectrum Space in the H. F. Bands

Since all current h.f. band space is actively occupied by one or
another mode of operation and since no current class of user is
willing to give up space for another, the Committee is operating
under the assumption that whatever rules are proposed there will
not be a sudden significant change in the way the bands are
currently used (at least this Committee is not prepared to make any
such recommendation!).  The Committee believes that gradual changes
will continue to occur but that these changes will be due to
natural migration as a larger percentage of amateurs shift to
digital from other modes of operation and from one digital mode to
another.

The respondents to the survey strongly opposed the allocation of
sub-bands by rule.  The Committee also believes that any attempt to
specify by rule sub-bands for a class of digital operation would
soon grow obsolete as patterns of operation change, more digital
modes are introduced, and more users shift to digital modes. 
Instead, the Committee believes that the amateur community will
need to adjust itself to continued sharing of the spectrum by
various modes and that such sharing should be facilitated through
the publication by the ARRL of recommended sub-bands for the
various modes and that such recommendations should be revised from
time to time as operating patterns change.

The Committee, as a subsequent action, will propose a revised band
plan for consideration by the ARRL.

In any case, the h.f. spectrum is severely limited, especially for
digital mode operation, and modes of operation that improve
spectral efficiency must be strongly encouraged.  The Committee
will undertake a study proposing, in a subsequent action, voluntary
technical standards which can be promoted among amateurs and
vendors to significantly improve our current frequency usage.


The State of the Art for Amateur HF Digital Operation

While the current rules allow considerable latitude in what digital
modes the amateur community uses, the actual practice is somewhat
limited.  Current practice includes "RTTY", a non-error-protected
simplex mode, usually using the baudot code; "AMTOR", a partially
error-protected half-duplex mode using the baudot code; "packet",
an error-protected half-duplex mode using ascii code; and "PACTOR",
an error-protected half-duplex mode using ascii code.  In addition,
a new DSP-based system has been demonstrated but is not yet
generally available called "Clover" that is an error-protected full
-duplex highly spectrum efficient mode.

As currently used all of the above modes require approximately 500
to 1000 Hz. of bandwidth per channel except packet which requires
2000 Hz. per channel.  Effective use of that bandwidth is terms of
character throughput varies considerably as a function of the
protocol used and the channel conditions.  Partly because of the
requirement for 2000 Hz. of space per channel and partly because of
the nature of the AX.25 protocol, the performance figures for
packet are the poorest per unit of bandwidth of any of the
currently used modes.  RTTY and AMTOR are better, and PACTOR is
better still.  Clover promises to exceed the throughput per unit of
bandwidth of any of the above modes.

Tolerance to poor channel conditions also varies among the modes
with packet having the poorest performance, RTTY next, AMTOR and
PACTOR being very much better.

Digital techniques for h.f. operation are improving and newer
technologies such as PACTOR and Clover promise significant near-
term improvements in spectrum utilization, throughput, and
performance under difficult h.f. radio conditions.  The current
rules do not appear to have contemplated these new modes in the
h.f. portion of the spectrum and the Committee believes the rules
require a modest change to encourage these and other new more
effective digital modes and to promote operation in the narrowest
possible bandwidth.

Potential Abuse of Unattended Operation

A few respondents to the Survey expressed opposition to any form of
unattended operation because of possible illegal use of amateur
bands for unauthorized third-party traffic, commercial purposes, or
the support of illegal activities such as drug smuggling.

The Committee is not aware of any pattern of such abuse nor does
the Committee see any reason why illegal operation is not just as
likely to occur directly between two attended stations as any
other.  The Committee did not consider this factor in making its
recommendations.



Competing Interests for HF Spectrum Space

The most difficult issue the Committee has had to deal with is the
demand for spectrum space from the many different classes of users. 
Many of these users are sharing (somewhat unwillingly) the same
space and each would like the others to vacate to other locations.

The most critical frequency bands (at the moment!) are 20 and 40
meters.

On 20 meters the frequencies above 14,100 kHz. have been
traditionally used for DX voice and below 14,100 KHz. for c.w. and
data.  With the advent of packet, and the STA authorizing
unattended packet operation, packet operations began above 14,100
Hz. and has gradually occupied the region of 14,100 to 14,125 Hz. 
Due in large part to the fact that data is not allowed in this sub-
band in some countries, packet operation has also extended downward
into the band immediately below 14,100 attracting US operation in
this sub-band as well.  Non-US voice operators have taken exception
to the use of the 14,100-14,125 space and RTTY operators have taken
exception to the use of the space below 14,100.

On the 40 meters packet operation began in the 7080-7100 Hz. region
where traditionally RTTY and AMTOR operators had been active.  This
has forced the RTTY and AMTOR operations further down into the
dismay of c.w. operators.  This picture is further complicated by
the fact that outside of region 2 data operation must be confined
below 7050 kHz.

The situation on other bands, especially below 21 mHz., though not
as critical as on 20 and 40 meters, have similar conflicts.  The
informal 'sub-bands' used by the various modes are also somewhat
fluid as propagation conditions change and usage shifts from one
mode to another.

The Committee does not believe that any subdivision of the bands by
rule will best serve the amateur community in the long run.  It
also seems unlikely that any subdivision of the band by mode will
work on a world wide basis because of the differences in the rules
between regions and between individual administrations.  Any
subdivision of amateur bands by rule also imposes an unnecessary
potential enforcement burden on the FCC.

Amateur Operating Practices and Traditions

Except in a very few special situations it has long been the
tradition (and rule) that one amateur station must not willingly or
knowingly interfere with a contract already in progress regardless
of the mode of operation or the perceived importance of the
communications in progress.  It has also been a long standing
tradition that no station or group of stations 'own' a frequency. 
(Frequency 'ownership' has admittedly become a practice on certain
v.h.f. frequencies, but this practice has never been established on
the h.f. bands and the Committee strongly rejects the concept of
doing so now.)

On h.f. the use of sub-bands with various classes of operation
gravitating to specific locations is largely self regulating simply
by virtue of the fact that a station occupying a frequency is not
driven off the frequency by deliberate interference by a station
operating another mode.  (There are always isolated exceptions to
this but it is not condoned in the rules or by the vast majority of
amateur operators.)  As greater numbers of amateurs use a
particular mode that part of the band becomes recognized informally
as a mode-specific sub-band.  There is always a significant overlap
in the sub-bands between modes - packet sharing with RTTY, RTTY
sharing with AMTOR, AMTOR sharing with c.w., and so on.  The
greatest conflicts come where the overlapping modes have
significantly different bandwidth, i.e., AM vrs. ssb, packet vrs.
RTTY.

Types of Automatic Operation

Two types of automatic digital operation are under consideration
for use on the amateur h.f. bands.  One is fully-automatic 
operation where messages are passed between amateur stations
without any operator intervention and no operator may need be
present at either station.

The other is semi-automatic operation where messages are passed
between amateur stations with an operator initiating the contact
from one of the two stations.

Both fully- and semi-automatic operation is permissible today under
the rules provided there is a control operator present at both
stations.  (Stations authorized under the STA may operate
unattended.)

Digital operation with one station functioning in a semi-automatic
mode has long been a practice dating back to the '60s.

Fully-Automatic Unattended Operation

The proposal to authorize fully-automatic unattended operation
represents distinct departure from past practices.  A clear
majority of the respondents to the survey opposed any fully-
automatic operation on the amateur h.f. bands.

To authorize fully-automatic operation without restriction, as some
of the respondents to the survey advocate, would seriously
undermine the fiber of mutual cooperation that h.f. operation
requires.  The Committee rejects such operation as undesirable on
its face.

It was also proposed to authorize fully-automatic operation with
restrictions, either to the frequencies allowed, to a few
privileged stations, or both.  The committee saw no purpose in
limiting the frequency bands alone since the number of stations
that would attempt unattended operation would make the mode and
allocated frequency useless to everyone.  Limiting the number of
participating stations was also rejected by the committee because
there was no conceivable way to equitably allocate the privilege to
specific stations nor was the committee willing to set aside any
portion of the band to stations with special privileges.

Fully-automatic operation, by it's very nature is mode-specific and
must 'own' the frequency it operates on an cannot be effectively
shared by other modes of operation.

To authorize fully-automatic operation on the necessary mode-
specific sub-bands raises serious problems.  There are no likely
sub-bands that can be used on a world-wide basis or that will not
cause interference to other users under some circumstances.

The only mode of operation that is currently a prospect for fully-
automatic authorization is packet, based on the AX.25 protocol,
using 2 kHz. channel spacing.  This mode delivers the poorest
performance with respect to spectrum utilization or survivability
under adverse propagation conditions of any the digital modes
currently in use. j The Committee does not believe that, if a
protected mode-specific sub-band is to be authorized, that it
should be a mode that is as inefficient in its resource utilization
as current packet practice represents.  Such an authorization will
discourage the development and use of a more suitable mode.

Further, the Committee does not believe that these is any service
being provided by fully-automatic operation that is not also
available by other means without the associated problems of fully-
automatic operation.  Nor does the Committee know of any reason why
packet operation cannot also be operated in semi-automatic mode,
thereby eliminating the need for a rule-mandated sub-band.

Semi-Automatic Unattended Operation

There are many reasons, however, why some form of automatic digital
operation is desirable.  It permits amateurs to exchange
communications when there is a time difference between the
operating times available to the two amateurs, and it permits the
quick exchange of messages rather than taking air time with long
calls and keyboard-to-keyboard operation.  (This not a suggestion
by the Committee that keyboard-to-keyboard is undesirable but
simply that there are many cases where moving messages at machine
speeds is more spectrum efficient and makes more frequency time
available to direct keyboard operation.)

It is very evident that some form of automatic operation is highly
desirable when handling NTS and personal messages between amateurs
through intermediate stations.  This capability forms the very
heart of the amateur community's preparedness for emergency
service.  Respondents to the survey favored semi-automatic
unattended operation over those opposed by a two-to-one ratio.

The Committee does recognize that there is some potential for
interference using a semi-automatic unattended mode even as there
is such potential in purely manual modes.  However, so long as
there is a control operator present at one end of the link,
monitoring the progress of an exchange, such interference can be
held to a minimum.  The benefits of semi-automatic operation
outweigh the risk of inadvertent interference.

The Committee believes that in view of the long successful history
of semi-automatic operation that authorizing unattended semi-
automatic operation is in the best interests of the amateur
community.

                         RECOMMENDATIONS

I.   Unattended fully-automatic operation of amateur digital
     stations should not be authorized below 30 mHz.

II.  The FCC rules should be amended to allow unattended semi-
     automatic operation of digital stations on any frequency on
     which digital modes are authorized.  Unattended semi-automatic
     stations may not initiate a contact, either with another
     station or via an undirected broadcast.  An operator
     initiating a contact with an unattended station must first
     ascertain that no interference will be caused to existing
     communications, and must monitor the progress of
     communications.  If it becomes evident that the communications
     with an unattended semi-automatic station is interfering with
     other amateur communications then the link with the semi-
     automatic station must be discontinued.  An unattended semi-
     automatic station must be equipped with a time-out timer to
     insure that no signal is transmitted longer than five minutes
     in the event of the malfunction of control equipment or the
     loss of contact with the initiating station.  Suggested
     wording for such an amendment is included in the appendix.

III. The FCC rules should be amended to allow the use of modem-
     dependent codes for the purpose of efficient data compression
     and error control on h.f. radio channels.  The bandwidth of
     such signals should be restricted to 500 Hz, below 28 mHz, and
     2000 Hz. between 28.0 and 28.3 mHz  The appendix to this
     report suggests specific wording for the recommended rule
     change.  A station using a modem-dependent code must still
     comply with 96.119 Station Identification.

IV.  The League should publish a comprehensive tutorial-style
     operator's guide for h.f. digital operations clearly defining
     acceptable operating practices.  Such a manual would delineate
     currently used informal sub-bands for the various modes and
     styles of operation, and the good operating practices that are
     required for effective mutual cooperation and coexistence. 
     This Committee will make specific recommendations for the
     content of this guide.

V.   The League should publish technical standards or guidelines
     for the characteristics of signals generated by digital mode
     stations for the purpose of achieving the best possible use of
     the h.f. spectrum.  QST should be used as a forum to educate
     that amateur community on the benefits and means of achieving
     acceptable signal quality and should review the technical
     characteristics of digital mode products with respect to
     published standards.  This Committee will make specific
     recommendations for these technical standards.




                           APPENDIX A



The following is suggested wording for an addition to Part 97
authorizing unattended semi-automatic digital mode operation.

97.3 Definitions

     ( ) Unattended Digital Station - A station in the amateur
     service using an RTTY or data emission that is operated
     without a control operator present.

97.216 Unattended Digital Station

     (a)  Any amateur station licensed to a holder of a General,
     Advanced or Amateur Extra Class operation license may be an
     unattended digital station.

     (b)  An unattended digital station may operate on any
     frequency below 30 mHz. that is authorized for RTTY or data
     emission for the class of operator license held.

     (c)  An unattended digital station may only use those RTTY or
     data emissions authorized by 97.305 and 97.307.

     (d)  No unattended digital station may initiate a contact with
     another station or may broadcast any undirected signal.

     (e)  The transmitter of an unattended digital station must be
     equipped with a time-out timer that will insure that no signal
     is transmitted for longer than five minutes in the event of
     the malfunction of control equipment or loss of contact with
     the initiating station.

     (f)  Any amateur operator initiating contact with an
     unattended digital station must first ascertain that no
     interference will be caused to existing communications, must
     be present for the duration of the contact, and must
     discontinue the contact if it becomes evident that
     communications with the unattended digital station is
     interfering with other amateur communications.




                           APPENDIX B



To encourage improvements in digital mode communications and
especially to improved spectrum utilization on amateur h.f. bands
Part 97, 97.307 (f) (3) and 97.307 (f) (4), should read as follows:

     (3)  A RTTY or data emission using a specified code listed in
     97.309 (a) of this Part may be transmitted.  The symbol rate
     must not exceed 300 baud, and for frequency-shift keying, the
     frequency shift between mark and space must not exceed 300 Hz. 
     A RTTY or data emission using an unspecified digital code
     under the limitations listed in 97.309 (b) of the Part also
     may be transmitted.  If an unspecified digital code is
     transmitted the authorized bandwidth is 500 Hz.

     (4)  A RTTY or data emission using a specified code listed in
     97.309 (a) of this Part may be transmitted.  The symbol rate
     must not exceed 1200 baud, and for frequency-shift keying, the
     frequency shift between mark and space must not exceed 1 kHz. 
     A RTTY or date emission using an unspecified digital code
     under the limitations listed in 97.309 (b) of the Part also
     may be transmitted.  If an unspecified digital code is
     transmitted the authorized bandwidth is 2 kHz.
From: myers@hpfcso.FC.HP.COM (Bob Myers)
Date: Mon, 27 Jul 1992 22:54:30 GMT
Subject: Re: Truckers using 2m for business...
Organization: Hewlett-Packard, Fort Collins, CO, USA