[NLRS] More 222 & Up contest .....

[Glen Overby]

I haven't tried FT4 or FT8 on microwave bands, but I have used JT4. JT4
uses 4 tones and the sub-modes (A-G) change the tone spacing. I don't
recall the spacings in hz, but I don't think I ever got a successful copy
on 10ghz with JT4A or B; I've usually used F, whose tones are clearly
separated on the waterfall display. Drift can be, I think, a full tone's
separation (that is, if the tone separation is 100hz, you can drift 100hz
during the transmission and it will copy). I worked Barry on my 5ghz system
that uses a MicroLO (crystal) and we were able to chase each other across
the band by tuning by hand (fun once, wouldn't want to do it all day). My
2304 and 3456 systems have external amplifiers and aren't as affected by
heating during transmissions. JT4 transmissions are 58 seconds, so that
might not be the mode you're looking for.

I think the use of FT4/8 on microwave bands comes down to the stability of
the oscillator. Transverters with external amplifiers will be more stable
than ones with internal intermittent heat sources. It's worth a try.

I haven't looked at the wsjt-x code, but the JT4 code in the earlier wsjt
program was written in fortran 90, and like all good fortran programs it is
self-documenting (by that I mean there are essentially no comments in the
code).

Glen


On Wed, Jul 22, 2020 at 1:24 PM Jon Platt via NLRS <nlrs at mailman.qth.net>
wrote:

> How many people used digital modes during last years 222 & Up contest?  I
> assume it was FT8 (for terrestrial)?
> After reading the QEX article on FT4/FT8, although FT4 surrenders ~ 3 dB
> to FT8 in terms of sensitivity I wonder if its greater frequency spread
> between tones would provide higher reliability in decoding, especially the
> higher in bands you go where frequency spread increases.  Anyone have any
> experience with this to share?
> 73, JonW0ZQ
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