ARRLWeb: ARRL Ad Hoc HF Digital Committee

ARRL Board of Directors
American Radio Relay League
225 Main Street
Newington, CT, 06111-1494

Please find attached the final committee report from the Ad Hoc HF Digital Committee that was formed at the request of the Board at the July 2002 meeting.

The committee met continuously via email from December 31, 2002 until it adjourned March 24, 2003. The committee has tried hard to represent the interests of the amateur community as large as well as those of digital operators.

Digital operation is one of the fastest growing areas in amateur radio today. It embraces all that the younger generation considers important, to include the computer, digital messaging of all kinds, and the Internet. I believe that we are just on the outer edge of these technologies and these developments may become the mainstay for the future of amateur radio. These are the modes of operation and interests that will bring the next generation of radio amateurs into the fold.

Change is difficult and our recommendations advocate change from past modes of operation but we are not the first to try and face these issues. I would like to quote from Lyle Johnson, KK7P, and the former president of TAPR (from TAPR's "HFSIG" list in 2002:

"In 1977 the FCC tried to eliminate modes and make the HF band segments based on bandwidth only. There was a HUGE hue and cry raised by the amateur community, and in the end all we got was approval to use ASCII. When we did packet in the early 80's, we initially just sent text so that packet could be deemed to be ASCII...

"In the mid-80's we (at that time I was on the ARRL Digital Committee) tried to get the rules changed to allow bandwidth-related modes on HF, or at least in some sub-bands. Once again, the "old guard" makes a lot of noise. 'That's where I run AMTOR. You're gonna interfere with my RTTY. Hey! I want to operate CW there...', 'CW is the most efficient mode of Amateur communications! Etc...'

"Hard to interpret? Well, let's say I have a way to send digital voice in a 3 kHz bandwidth. Do I do this in the phone bands (it is voice, after all) or in the non-phone segment (it is data, after all). This is the same mentality that causes people to think that warehousing valuable spectrum in little-used, 'closed' repeaters is somehow in the spirit of Amateur radio."

Perhaps the time has finally come. We need rules that are flexible enough to embrace innovation of all kinds and we believe these recommendations will take us a long way in that direction.

One final note: One member of the committee, Howard Teller, KH6TY, strongly disagrees with much of what the committee has done and recommends. He has advised the committee that he will submit his own report directly to the ARRL Board.

Report of the ARRL Ad Hoc HF Digital Committee

Prepared by Victor Poor, W5SMM, Committee Chairman

Committee Members:
Stan Horzepa, WA1LOU
Howard Teller, KH6TY
Steve Waterman, K4CJX
Melvyn Whitten, K0PFX
Peter Martinez, G3PLX (Resigned 2/28)
Tom Frenaye, K1KI, Board Liaison
Steve Ford, WB6IMY, Staff Liaison

March 24, 2003

The ARRL Ad Hoc HF Digital Committee was formed to advise the ARRL Board on issues that have arisen from the development of new HF digital data modes of operation. The committee is charged specifically with recommending how voice-bandwidth data modes should be introduced (Task 1), what changes if any are required to the FCC rules Section 97.219 with respect to interconnecting Internet with amateur radio digital operation (Task 2), and what changes if any are required to the FCC rules Section 97.221 with regard to automatic operation on HF (Task 3).

There are a number if issues to be faced as new digital signaling techniques and protocols are introduced into the HF amateur bands.

Region 1 is moving in the direction of specifying sub-bands by bandwidth only -- not by the signaling method or content of the signals. This committee has taken a similar outlook. As time goes on it will be become increasing difficult to distinguish between digital voice, SSTV and other imaging, FAX, text data, and other 'data'. Trying to draft rules that keep up with all of the possible uses and protocols amateurs use now or in the future is a futile undertaking. The committee believes that amateurs should be able to use whatever (publicly disclosed) protocols and modes they choose provided they operate within the appropriate sub-bands and otherwise adhere to FCC rules and good amateur engineering and operating practice. Natural clusters of common interests will form as they always have and will expand and contract as interests and application demands change.

Eliminating specific protocols or modes of emissions from the rules will provide more freedom for the amateur community to develop and experiment with new methods and techniques, digital or otherwise.

1. The 300 symbols per second limitation specified in 97.307(f)(3) and the 1200 symbols per second limitation specified in 97.307(f)(4) should be eliminated. Other rules specifying specific data modes, protocols, or character sets should be eliminated.

2. In place of 1 above, the rules should specify that below 28 MHz digital data signals must not exceed 3000 Hz bandwidth (measured at 26 db below mean power output.) (Note: This is a proposed regulatory upper limit for any digital data signal below 28 MHz. The bandwidths of 200, 500, and 2700 HZ mentioned below are nominal bandwidths applicable to voluntary subbands.)

3. Digital data signals should not occupy any more bandwidth than needed to efficiently transmit the data rate desired. This is already covered in the rules in 97.307(a) and (b) but is included here for emphasis. (Note: There was discussion of what constitutes efficient use of bandwidth but no simple rule could be articulated. There are numerous trade-offs between bandwidth, data rate, deliberate redundancy to improve robustness, and etc. The best that can be said is 'good amateur engineering practice'. By way of example using 2700 Hz to send data at 50 bits per second was not considered good practice but using less than 200 Hz was. The threshold was somewhere in between, at least on today's standards, but perhaps not tomorrow's!)

4. Below 28.0 MHz the digital data bands should be segmented by nominal bandwidths of 200, 500, and 2700 Hz where the bandwidth given is an upper limit only.

5. To the extent possible below 28.0 MHz the narrowest bandwidth segments would be at the lower limit of each band with increasing bandwidth with increasing frequency. (Note: See Attachment A. Some exceptions to this guideline need to be made to accommodate different frequency allocations in different regions.)

6. Digital data band segmentation should be voluntary and supported by the ARRL and the IARU in Region 2.

7. To the extent possible, given the differences in operating practices and available spectrum, digital data band segmentation should be harmonized between Regions 1, 2, and 3.

8. Any digital data protocol used must be publicly disclosed with sufficient detail that anyone skilled in the art could duplicate it. It is recommended that the ARRL staff develop the means of disclosure.

9. A digital data protocol that is not publicly disclosed should be allowed for brief periods of time provided that the transmitting station identifies itself clearly with CW or SSB where SSB is allowed. (Note: Stan Horzepa, WA1LOU, argues that the ID should also include an identifying name for the undisclosed protocol.)

In addition to the above, the committee has drawn a proposed voluntary band plan that would accommodate the voice-bandwidth digital modes in a way that would be harmonious with existing operations and where possible would harmonize with the latest proposed Region 1 band plan. This is attached as Appendix A.

Internet has impacted how we interact in many ways and has dramatically changed the way we look at communications. This committee believes that amateur radio should embrace Internet technology, and take every advantage of what it has to offer in order to extend and improve the value of our hobby. We see nothing in the current rules that inhibits our use of Internet.

Rules governing the interconnection between Internet and digital systems are effectively covered in Section 97.219 and provide the needed protection against extending Internet into amateur radio in a way that would harm the hobby through commercial exploitation. The section as currently drawn was driven by the needs of the AX.25 community a decade ago, but is equally applicable to interconnection with Internet today.

It is the unanimous recommendation of the committee that Section 97.219 remain unchanged.

The committee has addressed two modes of automatic operation with respect to the HF bands. One is fully-automatic or machine-to-machine operation where signals are transmitted without a control operator attending at either station. The other is semi-automatic or human-to-machine operation where transmitted signals are only initiated by an attending control operator at one of the two communicating stations. Section 97.221 provides for both modes of operation.

Fully-automatic operation on HF was initiated a decade ago to provide for the unattended forwarding of messages using AX.25. At the time Internet was not generally available to the average ham and message forwarding on HF between local networks of VHF AX.25 stations was seen by some as the only practical means of maintaining a national (or international) messaging network. The wide spread availability of Internet has changed this.

Because fully-automatic operation presents technical problems on HF that make bandwidth sharing with other modes and uses virtually impossible alternatives should be used if at all possible. Internet is now available worldwide and can provide that alternative. The forwarding of packet messages over Internet is a practice that is already being widely used by radio amateurs and should be encouraged to relieve congestion on the HF bands where HF radio links are not essential.

The committee recommends that fully-automatic, unattended machine-to-machine operation be phased out of the HF bands below 28 MHz and the spectrum that has been set aside below 28 MHz for fully-automatic operation (97.221(b)) be returned to general use.

Semi-automatic human-initiated links with automatic unattended stations should be preserved however. This has been common practice since the earliest days of RTTY operation where RTTY stations established auto-start networks for passing messages.

Any digital data operation where the data rates exceed typing speeds is going to be used in this way even if an operator happens to be present at the station being called. Only the operator initiating a link can ensure that the frequency is free. When operating at data rates above typing speeds it would be difficult to distinguish between links where an operator was only present at the initiating station and where one was present at both stations. Higher speed modes are to some degree always 'automatic' since they are machine-to-machine transmissions and certainly no less so at voice-bandwidth speeds!

There is another significant advantage in using semi-automatic operation. It allows a large number of users to pass messages using only a limited amount of bandwidth. Compare a high speed digital message server with a SSB voice network and you will find that many more users can handle far more queries and messages than if they were handled by voice or by establishing separate keyboard-to-keyboard contacts on separate digital frequencies. The fast get-on-and-get-off nature of semi-automatic operation is a great saver of bandwidth and air time allowing far more digital users to participate than would be possible if it were not allowed.

There is only one way to effective and courteous communications and it is no less true whether person-to-person or machine-to-machine -- LISTEN FIRST! This has to be the first rule for any mode of operation.

Today, there are literally thousands of digital operators using semi-automatic operation and attempting torestrict this practice would be unreasonable and would result in a serious revolt with current operators, and even more importantly, would restrict new enhanced digital operations in the future.

The rules currently restrict semi-automatic operation to digital modes of 500 Hz bandwidth or less (97.221(c)(2)) except in the fully-automatic sub-bands. With the phasing out of fully-automatic operation and the advent of voice-bandwidth data modes the 500 Hz bandwidth limitation should be eliminated.

The committee recommends that semi-automatic, human-to-machine operation continue to be permitted in the rules and that the current 500 Hz bandwidth limitation for automatically controlled stations be eliminated. The bandwidth of an automatically controlled station should be governed by the voluntary sub-band in which it is operating.

The Ad-Hoc Digital Committee wishes to express its appreciation for being invited to present its experience and input to the Board.

Attachment A to the Report of the ARRL Ad Hoc HF Digital Committee

March 24, 2003

This is a proposed band plan developed by the committee to incorporate future voice-bandwidth data operation. It also goes a step further and proposes that all sub-bands below 28 MHz within the amateur spectrum be defined by nominal bandwidth alone -- not by any specific mode of operation or content.

It is recommended that good operating practice call for digital operators in the 'C' (voice-bandwidth) segments to limit their operation to the low ends of the segments and work upwards when and if activity expands. Likewise, good operating practice would request digital operators in the 'A' (200 Hz bandwidth) segments limit their operation to the high end, working downward as activity expands.

In this plan, it is assumed that 300 baud FSK signaling is limited to 'C' segments due to its transmitted bandwidth. This is not to say that AX.25 could not be used in 'B' segments if a more efficient signaling mode was used that remained within 500 Hz bandwidth.

Current North American practice is for data modes to use 1800-1810, frequencies that are apparently denied in Region 1. There shouldn't be any conflict there.

The current 'wall' between narrow and wide modes in North America is 1843. The two data exclusive bands in the Region 1 proposal are a puzzle. Here is an opportunity to harmonize with North America and set 1838 to 1843 as an all mode 'B' segments, set 1843 to 1999 as an all mode 'C' segment, and set 1999 to 2000 for beacons.

This plan harmonizes as well as can be expected with proposed Region 1 plan on 80 meters and does not force any change in current practice in North America either.

This does not match Region 1 proposal very well, but it does mirror current practice in North America (other than extending the 2700 Hz segment down to 7100).

On this band and the Region 1 proposal and this proposal differ significantly. There is currently a lot of data activity on 30 meters especially in North America, and it continues to expand. 30 Meters is proving to be one of the most useful and effective bands for data. 500 Hz data modes as well as modes requiring more than 500 Hz (currently APRS packet, packet auto-forwarding, and, Pactor III) are being used. Confining all data to 10 KHz as proposed in the Region 1 plan will not work. There is simply no way the proposed Region 1 plan could or would find acceptance in North America. On this point Region 1 has to give a little -- either by accepting that more spectrum will be used for data in North America or by opening up more in Region 1.

The 'no voice' limitation to the 2700 Hz segment on 30 meters is included since voice is not allowed on 30 meters by current FCC rules.

Packet auto-forwarding should be moved to the lowest 6 kHz of the C segment if it continues to be allowed.

The biggest point of difference between this plan and the proposed Region 1 plan is the lower limit for the 'B' segment. There is well-established heavy use in North America (and elsewhere too for that matter) of the 14065 to 14070 segment for data. Region 1 should seriously consider setting the lower limit at 14065, also.

The proposed Region 1 plan also puts a wall at an upper limit of 14112 for 'all' and then opens up 14300 to 14350 to 'all' as well making an orderly expansion of the use of data difficult if not impossible. It would be much better to simply open 14101 to 14350 to 'all' and let data the data modes work up from the bottom gradually as usage increases.

Packet auto-forwarding should be moved to the lower 5 kHz of the 'C' segment in the 18 MHz band if it continues to be allowed.

Packet auto-forwarding should be moved to the lower 10 kHz of the 'C' segment in then 21 MHz band if it continues to be allowed.

Packet auto-forwarding should be moved to the lower 5 kHz of the 'C' segment in then 24 MHz band if it continues to be allowed.

Packet auto-forwarding should be moved to the lower 70 kHz of the 'C' segment in then 28 MHz band.