Re: Affecting the use of digital modes... #qrm

Matthew Chambers NR0Q

Personally I think they should have moved upwards rather than downwards as the x.070 to x.074 slice is still sometimes occupied by older narrowband digital modes such as PSK31 and it's variants and narrower versions of Olivia, along with MFSK. Why couldn't FT8 occupy x.074 to say x.078 with an overlap with FT4 from x.076 to x.078 and FT4 only up to x.080 for example. I recall that JT65 and JT9 had an overlap area with JT65 occupying the lower half and JT9 the upper half of the spectrum which worked well. A contiguous block of spectrum would make more sense for FT8/FT4 due to the nature of how those modes operate where we decode the whole swatch of spectrum at once. And with newer SDR technology, we could have a digital-USB bandpass that is 4-6 kHz wide vs the 2.8 kHz of most traditional radios, allowing us to see the whole FT8/FT4 suband at once. I'm not sure if the direction they were moving would allow for that contiguous block. As the number of digital modes is only going to continue to increase, finding ways for modes to share spectrum is going to need to become a higher priority.

Matthew Chambers, CBT, NR0Q
M Chambers Communications Engineering LLC
PO BOX 855, Moberly, MO 65270
Mobile (660)415-5620

On Mon, Jun 1, 2020 at 6:21 AM Tomas, NW7US <nw7us.heliophile@...> wrote:
Please see my two articles regarding an urgent issue involving all digital modes on HF, including FT8 / FT4.
Part 1:
More parts to follow...
Be sure to read the comments left on each post, as there are great points made in this discussion.

73 de Tomas, NW7US dit dit
Space weather and radio propagation editor for CQ Amateur Radio Magazine, and The Spectrum Monitor magazine. 
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