[600MRG] WSPR Modes

[Larry Molitor]

While K1JT may be trying to push new modes, I think he might respond to a large number of requests to allow WSPR-15 in the interim. Of course if everybody just sits here and complains without doing anything, we won't see any more WSPR-15 efforts from the development team.
Since, as a practical matter, WSPR-15 usually only gives about 3 dB additional decode sensitivity, there doesn't seem to me to be any justification for a "mid-speed" variation.
If you think about it for a bit, you can see that WSPR-15 has no real future on a populated band like 475 kHz. The long period causes more trouble than it's worth except for possibly a few guys experimenting at the edge of the band where they won't screw up everybody else. Of course it's a lot different on 188, 137, and lower frequencies.
Now here is where I'm going to really show my ignorance. K1JT has mentioned MSK and OQPSK as possible future beacon modes. My old brain sorta remembered these modulation schemes required linear amplifiers so why would Joe be looking at them? Since my personal reference library is dated before personal computers and DSP became prolific it didn't help. Some on-line research showed MSK to be "Minimum Shift Keying" and OQPSK to be "Offset QPSK". MSK clearly should work with a non-linear amp but I still can't get my head around how OQPSK does.
WSJT-X has, in the VHF modes, MSK144. According to the users manual, this is a high speed mode which has about a 2 kHz bandwidth, short periods, and implemented with an OQPSK modulation scheme. It seems to have become very popular with the 6 meter crowd.
If Joe and his team think they can get something like this modified to work well on LF/MF using class C/D/E amplifiers and very narrow band antennas, then I have to believe it. But I don't think it could be available for us to use anytime soon. And I don't expect any "conversational" modes at all (ever).
If somebody can point me towards an on-line reference that more clearly explains OQPSK I would appreciate it. At this point it's only of "academic" interest. I don't expect either new modes or amateur authorization to happen before I'm too sick or too dead to care.
73,
Larry - W7IUV / WH2XGP 


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