One of the responsibilities of the Technical Coordinator in the Ohio Section is to submit something for the Section Journal. The Section Journal covers Amateur Radio related things happening in and around the ARRL Ohio Section. It is published by the Section Manager Tom – WB8LCD and articles are submitted by cabinet members.
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Now without further ado…
Read the full edition at:
THE TECHNICAL COORDINATOR
Jeff Kopcak – TC
Finally, a step in the right direction allowing ham radio to modernize – being able to use and develop new data communication methods and have greater flexibility encouraging experimentation. Last month, an announcement from the ARRL recapped a ruling made by the FCC to amend the Amateur Radio Service rules. Commissioners voted unanimously to remove the symbol rate (baud rate) restriction replacing it with a 2.8 kHz bandwidth limit on the HF bands.
Émile Baudot was an engineer and inventor of the first means of digital communication called the Baudot code in 1870. Instead of using dots and dashes as used in Morse Code, he invented a system of bits to represent each character when transmitting messages over a telegraph line. The “baud” unit was named after him. Baud is the number of symbols transmitted per second across a medium. Baudot’s system allowed for multiple transmissions over a single line.
In modern electronics and computing, baud is often associated with serial communication. Most of us remember or have used serial ports. Stating a serial port operates at “9600 baud” means that serial port can transfer up to 9600 bits per second.
Telephone modems, such as those used to access BBS’ and early Internet, had baud rates that matched bit rates. As technology developed and faster communications were demanded, modems used multiple signaling events. The V.32 ITU-T standard allowed for data transfers at 9.6 kbit/s or 4.8 kbit/s at 2,400 baud. This means there were 4 or 2 signaling events respectively occurring at 2,400 baud to achieve the transfer rate.
In their decision, the FCC stated “baud rate limits were adopted in 1980, when the Commission amended the rules to specify ASCII as a permissible digital code. The Commission adopted the limits so that ASCII signals would occupy no more spectrum than traditional radioteleprinter signals associated with the use of Baudot code (FCC Amends Amateur Radio Rules for Greater Flexibility).”
Hams are (for the time being) limited to 300 bauds on the 2200m-12m bands. 1200 bauds on 10m. 19.6 kilobauds on VHF (6 & 2m) not exceeding 20 kHz. 56 kilobauds not exceeding 100 kHz on 220 and 440. A symbol rate is not specified for 33cm and above (97.305).
The ARRL’s petition asked the commission to delete all references to a symbol rate and establish a bandwidth limit of 2.8 kHz for data emissions below 29.700 MHz (2200 and 630-meter excluded). FCC commented that amateur radio can still play a vital role in emergency communications, but is hindered by current baud rate limitations. This ruling removes the old standard of ‘how much data can be sent per second’ replacing it with ‘how much data can be packed into 2.8 kHz of RF spectrum’ on the HF bands.
2.8 kHz occupies the same bandwidth as common side-band (voice) signals seen on HF bands. Even though sections permit wider transmissions (AM, FM in portions of 10m), the limit is imposed uniformly across all HF bands. 2.8 kHz was decided upon because placing the limit below 2.8 would preclude some modes that are already legal.
Radios that do not have a specific “digital” mode setting use SSB when transmitting digital signals from a computer or other device. Radios capable of SSB can be used when newer data modes are made available if offered in a traditional sound card configuration and the radio doesn’t have a hard roll off at 2.7 kHz that cannot be adjusted. Newer ICOM radios (like the 7300) and Software Defined Radios can transmit full bandwidth. Offerings may decide to use standalone hardware or a modem with the assistance of a computing device to transmit and receive signals.
The ruling did not change anything else. Only symbol rates below 29.7 MHz are affected. 6m and up are unaffected and remain at the published symbol rates in Part 97. The commission proposes removing baud rate restrictions in favor of bandwidth limits on MF, VHF, and UHF too. Band plans and sub-bands remain the same. Digital portions remain digital portions, voice remains voice. Band plans are not something the FCC rules on either. Band plans are typically established by gentleman’s agreement among hams. 2.8 kHz is a maximum. A single PSK or FT8 signal is not going to start utilizing all 2.8 kHz – though some operators act like it. Stations must still set audio levels correctly to reduce digital splatter from their station.
The ARRL previously stated they are in favor of bandwidth limits on other bands but wanted to review limits that might be imposed. I believe it gets tricky with modes of varying bandwidths. For example, many would probably say most popular on the 2m band is FM, including repeaters. There are 2m SSB sub-bands too. 6m is similar with the low-end being DX windows and the upper end being largely FM and repeaters. Could there be multiple limitations implemented per band? DX windows get a 2.8 kHz limit while FM portions are limited to 15 or 20 kHz? Maybe. One problem with this theory, existing permitted legal bandwidths (e.g.: 100 kHz) would be excluded. These and other considerations are likely being reviewed by the ARRL.
An immediate effect of the bandwidth ruling permits later PACTOR modes. In nearly every hurricane or disaster where hams are involved with emergency communications, the FCC would grant a waiver allowing greater than 300 baud transmissions. This temporarily allowed PACTOR III & IV transmissions, which are faster and more reliable than other modes. No more symbol rate waivers will be needed. I’m noticing more Winlink RMS stations in the U.S. listing 2750 Hz VARA HF. There was some question whether 2750 is legal under existing rules in the U.S. and these new listings could be in anticipation of the upcoming changeover.
PACTOR-III has a “data rate of up to 3600 bits per second and a symbol rate of 100 bauds” while PACTOR-IV is “capable of a data rate of 5800 bits per second … [at] a symbol rate of 1800 bauds (Amateur Baud Rate NPRM).” PACTOR-III would be permitted. PACTOR-IV, which does not occupy anymore bandwidth than PACTOR-III, is prohibited and not spectrally efficient.
The new rules go into effect 30 days after publication in the Federal Register. The document was published on December 7, 2023 with amended Part 97 rules. The new Part 97 HF bandwidth rules go into effect January 8, 2024!
Thanks for reading and 73… de Jeff – K8JTK