ad7i (12/06/82)
ad7i msg 26: A report that i submitted to the FCC on a HF RTTY
error correcting protocol follows.
-------
Thirty Victoria Place
Red Bank, N.J. 07701
201-949-3731 (W)
201-741-1151 (H)
November 23, 1982
Mr. Richard H. Everett
Chief, Licensing Division
Federal Communications Commission
Gettysburg, P.A. 17325
Dear Mr. Everett:
Enclosed is the report required by the S.T.A. outlined in your letter
of May 3, 1982. If I can provide any additional information, please do not
hesitate to contact me.
Sincerely,
Paul Newland
Copy (with att.) to
Vic Clark, W4KFC
Phil Karn, KA9Q
Bill Meyn, K4PA
Dave Sumner, K1ZZ
Curtis Williams, W5DTR
netnews
November 23, 1982
REPORT TO THE FEDERAL COMMUNICATIONS COMMISSION ON EXPERIMENTS
CONDUCTED BY PAUL NEWLAND AT AMATEUR RADIO STATION AD7I
USING THE ERROR CORRECTING PROTOCOL DESCRIBED BY CCIR
RECOMMENDATION 476-2
ABSTRACT
This report outlines the use of the teleprinter code described by CCIR
Recommendation 476-2, also know as AMTOR, by amateur radio station AD7I.
Use of this code during the period provided by Special Temporary
Authorization (S.T.A.), file 7130, was hampered by external influences. No
"scientific" data were collected but outstanding performance provided by the
CCIR 476-2 coding was observed by the operator on numerous occasions. The
report concludes with a recommendation that use of CCIR 476-2 coding by
U.S.A. radio amateurs be allowed as soon as possible.
DISCUSSION
This report describes use of the error correcting protocol described by
CCIR Recommendation 476-2 at my amateur radio station, AD7I, during the
period of May 1982 to November 1982. During much of the experimental
period, the High Frequency (HF) station was inoperative because of radio
problems. Additionally, I was required by business commitments to make
several unexpected and lengthy trips during the fall. Consequently, time
did not permit scientific data, per se, to be collected for presentation.
However, I have formed strong opinions about the usefulness of this mode of
communications based on my use.
In May of this year I completed construction of a microprocessor system
to convert the CCIR 476-2 signals to international telex teleprinter code.
The firmware to accomplish this code conversion was provided by Mr. Peter
Martinez, G3PLX; I designed the controller to be software compatible with
Mr. Martinez's firmware. An additional microprocessor system was designed
and built by me using a different manufacturer's microprocessor. I
programmed this second microprocessor to convert CCIR 476-2 Mode B to
international telex teleprinter code. I also purchased a new HF-SSB radio
to perform experiments with CCIR 476-2 coding. All other equipment was
previously on hand.
After completing the controllers, U.S. Coast Guard and Canadian Coast
Guard weather broadcasts were monitored to observe the print quality of
Forward Error Correction (FEC) mode B communications during normal HF
propagation conditions. In my opinion, without scientific data to back my
- 2 -
claim, I feel that the FEC mode of operation for broadcast use is superior
to that of conventional stop-start unprotected teleprinter transmissions
(RTTY). A major advantage of CCIR 476-2 coding in FEC mode is that detected
errors are converted to space characters by the code converter. Hence,
errors are easily and quickly spotted by the operator so fills can be made
from context.
On June 1, 1982, I advised the Commission's field office that on or
after June 11, 1982, station AD7I would begin transmissions using CCIR 476-
2. On June 13, 1982, contact was established with station TI3DJT using the
Automatic ReQuest for repeat (ARQ) mode A. From June 13 to 29, 1982, 39
contacts were made with radio amateurs around the world using CCIR 476-2
coding. Most of the contacts were made with ARQ mode A; only several
contacts were made using FEC mode B. All contacts took place on or near
14.075 MHz. Stations with which communications took place were: TI3DJT,
PA0RYS, HB9AUK, HB9AK, K4PA, G3PLX, A4XFW, G3RYS, KB6BT, KC7KK, and TI2CC.
On June 30, 1982, the station's radio was returned to the manufacturer for
repair under warranty. The synthesizer provided unreliable operation after
the radio had been on for several hours.
On September 28, 1982, the radio was returned in good working order.
>From September 28, 1982, to November 14, 1982, another 31 contacts were
made. In my opinion, again without scientific data to back my claim,
performance using CCIR 476-2 ARQ coding is VASTLY superior to conventional
RTTY coding. CCIR 476-2 displays an amazing robustness during conditions of
propagation that render SSB and CW modes of communications virtually
useless. I apologize for not having scientific data to back my claims; I am
sure that the data would substantiate my opinions. CCIR 476-2 consistently
provided communications during short and long duration frequency selective
fading, during SSB and CW co-channel and adjacent channel interference, and
during conventional Radio Teleprinter (RTTY) interference. The only
interference to which CCIR 476-2 is not immune, as one might expect, is
another co-channel CCIR 476-2 station. Such stations did not present much
of a problem during the test period. However, it is important to note that
there were few stations available to cause inadvertent or deliberate
interference.
IMPLEMENTATION
CCIR 476-2 proves to be a simple addition to an amateur radio HF RTTY
station. Figure 1 shows how the system components were configured at
station AD7I. The cost of the CCIR 476-2 code converter was about $40.00
due to a well-stocked junk box. If all components for the controller were
purchased new and the firmware was free, the cost for a code converter
should still be well under $85.00. This is a small amount of money compared
to other system components. Vast sums should not be required to implement a
CCIR 476-2 code converter.
- 3 -
CONCLUSION
The performance provided by CCIR 476-2 coding is superior to
conventional coding, and the incremental cost to add that capability to an
amateur radio RTTY station is low. I therefore recommend that the Federal
Communications Commission allow, as soon as possible, the use of CCIR 476-2
coding by radio amateurs who now have RTTY privileges.
Respectfully submitted,
Paul Newland, licensee of
Amateur Radio Station, ad7i