[600MRG] WSPR Flavors

[Larry Molitor]

All of these questions could be answered by reading and understanding ALL the documentation available for the WSPR mode.
WSPR-X is a bastard with many flaws and should not be used for anything except the WSPR-15 mode. 
All versions of WSPR and WSJT-X up to the latest ver 1.7 have exactly the same encoder/decoder and have exactly the same decode sensitivity. Over the various versions, the algorithm which approximates the "dB" number reported as S/N in a 2500 Hz bandwidth has changed. That "dB" number should not be used for comparison purposes except in certain very specific tightly controlled circumstances. In other words it should not be used the way most people are using it (as an absolute precision measurement system).
WSJT-X ver 1.7 has the new AN/JT decoder and can be a bit more sensitive. Mostly the difference shows up in dynamic range and the ability to decode multiple signals on almost the same frequency.
Varying the duty cycle does not in any way changed the decode sensitivity. However running more than 20-30% selfishly hogs time and spectrum so the inconsiderate station can "win" the spots contest.
"WSPR" usually refers to the WSPR-2 mode which has a 2 minute period. WSPR-15 has a 15 minute period and for various reasons is useless on HF and of limited use on 475 kHz but is very useful on the LF bands.
Also note that setting your radio to a narrow bandwidth does NOT help the software decode. It will screw up the measurement system that calculates the "dB" number making it even more useless than usual. The software uses internal filter bandwidths on the order of 1 Hz. However, if you have a crappy radio with poor dynamic range, you can help the radio with a narrow IF bandwidth in certain situations, but that has nothing at all to do with the software. The software works as designed with a RX bandwidth of 2.5 to 6 or more kHz.
Don't believe the above? Then you should read the docs and/or ask K1JT!
73,
Larry - W7IUV / WH2XGP

      From: Frank Lotito <k3dz at live.com>
 To: 600 / 630 Meter Group <600mrg at w7ekb.com> 
 Sent: Thursday, January 26, 2017 8:04 AM
 Subject: [600MRG] WSPR Flavors
   
I have been asking this question for a while regarding the different "flavors" of WSPR.  I'm confused - For as many people that I have asked, I get almost no unified answer.  I definitely get a fair amount of hesitancy, such as "er...., I think so...., maybe...."  Hopefully within the ranks of this column's readers one or more can answer this question from a standpoint of academic authority.


My question - On the receiving end, in order to maximize the ability to decode a WSPR signal, does the receiving station have to use the same "flavor" WSPR as the sending station?  By flavor I mean:  (1) The same transmit / receive duration in  the 10 minute cycle?  (2) The same revision, e.g., WSPR-X vs another version such as an early issue of WSPR that is a number of years old? (3) And on occasion, I have seen / heard stations referring to things such as WSPR-1, WSPR-1.2, WSPR-15, or whatever.  What are these and their impact on successfully decoding a signal if the receiving station is not using that same version (flavor) as the transmitting station?


I am not challenging the importance of items such limitations in the receiving or transmitting station's equipment, frequency drift, time synchronization, etc., the type and strength of adjacent and co-channel interference be it natural noise or a man-made emission, or, in the case of VHF / UHF / SHF reception, the more esoteric items.


73 Frank Lotito  K3DZ / WH2XHA
_______________________________________________
600MRG mailing list
600MRG at w7ekb.com
http://w7ekb.com/mailman/listinfo/600mrg_w7ekb.com