[Lowfer] Looking for 73 kHz band modes to try...

[JD]

>>> Opera is not legal to tx in the US, FCC thinks it is a spread-spectrum 
>>> mode.

Actually, Cliff, that's what its own, er, inventor called it, way back when. 
Perhaps they took his word for it.  It's not really SS, of course.  It uses 
no energy-spreading techniques; it's merely frequency agile.

But it's still not legal below 50 MHz in the US amateur service for a much 
more fundamental reason...the same reason WSPR and PSK31 and others *do not* 
meet the published Part 97 requirements on HF, either!

In 160m and all relevant segments of the HF bands through 12 meters where 
RTTY and data are permitted by Sec. 97.305, Note 3 of 97.307(f) also 
applies:  "Only a RTTY or data emission using a specified digital code 
listed in §97.309(a) of this part may be transmitted. The symbol rate must 
not exceed 300 bauds, or for frequency-shift keying, the frequency shift 
between mark and space must not exceed 1 kHz."  (At 10m, it's Note 4 
instead, which is exactly the same except for a 1200 baud symbol rate.)

Well, obviously the baud limits and the maximum frequency shift are not the 
problem.  But if you follow on to 97.309(a), you find that there are only 
three coding methods specified for RTTY and data emissions...5-level Baudot, 
AMTOR, and ASCII.  That's all!

Unspecified codes _are_ permitted by Notes 5 and 6, but those notes apply 
only within bands above 50 MHz.  Thus, OPERA and the other aforementioned 
modes are legal up there, with a few restrictions.  And, Part 5 licensees 
are not under the requirements of 97.309(a) at all, so there's presently no 
problem using any of these modes in the US at LF and VLF.

(QRSS employs International Morse, the coding method explicitly defined for 
CW in 97.3(c)(1) and permitted virtually everywhere in the ham bands by 
97.307(a).  Hellschreiber is an image mode, on which few specs are stated in 
the Rules other than bandwidth limits, so no problem there either.)

But assuming we do someday get 2200 and/or 630 meters in the amateur 
service, one of two things will need to happen before it's legitimate to use 
popular digital modes in those bands:  (1) there will need to be yet another 
new slow mode that does, in fact, utilize one of the currently specified 
codes; or else, (2) developers of this sort of software will need to get 
together and agree on a nice, efficient varicode they can all get behind, 
publish it, and then petition the FCC to include it in the specified codes 
of 97.309(a).  I have no doubt most of us here would gladly support such a 
petition.  Then some variant of each of these worthwhile digimodes would be 
legitimate for American ham use in all bands.

73
John