Ok, per your request, here's Joe Taylor's first reply (thank you, Joe! :-).
My second question --and Joe's reply-- follows, below the first reply. 73, Mike www.w0btu.com On Mon, May 15, 2017 at 7:58 AM, Joe Taylor <[email protected]> wrote: > On 5/14/2017 11:36 PM, Mike Waters wrote: > >> Ok, what is the truth here? Is JT9 better than JT65 on 160m, or is it >> inferior?? >> > As you should expect, the correct answer is "it depends". Depends on conditions of propagation, QRM, etc. On an ideal AWGN (additive white gaussian noise) channel JT9 has a 2 dB advantage over JT65. But the JT65 code has more redundancy than that in JT9, and the 2 dB advantage tends to disappear on a fading channel. JT65 is more robust than JT9 in the presence of QRM (and possibly QRN?). Overlapping JT65 signals are readily decoded. Not so much for JT9. Savvy operators using JT9 often respond to a CQ or tail-end "up" or "down" by 20 Hz or so, thereby avoiding calling on top of another caller. I don't subscribe to [email protected] or [email protected], but you may re-post this message there if you choose. -- 73, Joe, K1JT On Sat, May 13, 2017 at 5:50 PM, Brian D G3VGZ <[email protected] <mailto:[email protected]>> wrote: ... I find the better ability for JT65 to decode co-channel signals with its two pass decoding makes up for any 2dB improvement in decoding JT9. I also find a single static crash can take out JT9 decodes, more so than JT65.* * That certainly got my attention! Has anyone else experienced this? *And if so, what filter were you using: the wide SSB filter or a narrower CW filter?? *I'm inclined to think that JT9 is superior to JT65 on 160m. /But I have an open mind. [snip] ===================================== *Okay, here is another question, and Joe's reply:* ===================================== On Tue, May 16, 2017 at 9:46 AM, Joe Taylor <[email protected]> wrote: Hi Mike, ... I would like to know if this is true regardless of what the bandwidth > and shape factor is in the receiver itself. The state of the art in SDR can > create an almost perfect filter with zero ringing /no matter what the > bandwidth is. > > I realize that the SSB filter is great for browsing the JT* signals, but > what about narrowing the signal after establishing a JT9 contact, when > there are no overlapping signals? > An SSB receiver is a linear device: typically a series of amplifiers, filters, frequency mixers, etc. As long as things remain linear, it doesn't matter in what order these things are done. There is NO advantage to using a narrow filter ahead of WSJT-X, because the program already uses digital filters tailored exactly to the needs of the protocol. Final detection and measurement bandwidths for the JT65 and JT9 tones are equal to the baud rates, 2.692 and 1.736 Hz respectively. -- 73, Joe, K1JT _________________ Topband Reflector Archives - http://www.contesting.com/_topband
