Dear "Rik van Riel", There is currently no finite bandwidth limit on HF data/text emission in USA ham bands, except for the sub-band and band edges.
FCC data/text HF rules are still mainly based on content of the digital emission, not bandwidth. FCC rules allow hams to transmit a 149kHz bandwidth data/text signal on the 20 meter band. It may not be popular to do so, but it is legal :) The amateur radio regulations of many other countries of the world do not have bandwidth limits on signals. Bandwidth regulation has been recently adopted by some countries. New SDR radios have the potential to transmit and receive wider bandwidths. Perhaps we will see more development in this area of technology in the future. There are other HF services using 24kHz and 48kHz bandwidth fast data modems. Some of these modems are capable of sending a page of text in the time it would take you to call CQ on one of the slow digital modes. Perhaps there are good applications for 48kHz modems in HF ham radio. For example, large portions of the 24MHz, 21MHz, and 28MHz ham bands are almost completely empty of amateur radio signals for years. It would be easy to fit a 24kHz or 48kHz bandwidth signal in these bands. Rik, you recently wrote that "FCC part §97.307 places" [bandwidth] "limitation on any data mode transmitted in the HF bands" Please check your copy of the FCC rules more closely, because you overlooked what the rule actually says: "(f) The following standards and limitations apply to transmissions on the frequencies specified in §97.305(c) of this Part." §97.305(c) is a chart of amateur radio bands and sub-bands. Each sub-band has a "note", and the notes are listed in part §97.307. The Note # (2) only applies a soft bandwidth limit to non-phone emissions within the "Phone,image" sub-bands. Note # (2) does not apply to the CW/data/RTTY sub-bands. Several years ago, there was a proposal to FCC to provide regulation by bandwidth rather than content. However, it failed to be adopted. Thus, USA hams still don't have a bandwidth limit for HF data/text :) Best Wishes, Bonnie Crystal KQ6XA > Rik van Riel <r...@...> wrote: > Furthermore, from part 97.307 places this limitation on any > data mode transmitted in the HF bands: > > (2)No non-phone emission shall exceed the bandwidth of a > communications quality phone emission of the same > modulation type. The total bandwidth of an independent > sideband emission (having B as the first symbol), or a > multiplexed image and phone emission, shall not exceed > that of a communications quality A3E emission.