[600MRG] Quartile Method of Characterizing 630m Propagation Paths: Part I

[James Hollander]

I'm trying out a method of using the WSPR database of SNR data to learn more about the 630m propagation in different directions on the same path and different paths.  

Information is shown about specific paths between some 630m stations from last night  2/11/15.  

If you have comments or critique, or would like me to do calculations for a path you care about that might not be shown in a later part of this post, e-mail me direct at mrsocion at aol.com.  Will do what I can.

73,  Jim H   W5EST 

QUARTILE METHOD FOR VARIABILITY V AND dB TILT T
   Characterize propagation paths on theassumption that a propagation path itself has some variability.  By contrast, TX power, RX performance andtx/rx antennas are constant dB contributors to SNRand generally lack variability.  (The methodwould not apply to a decoding run when physically-rotatable and/orelectronically rotatable antennas are dynamically adjusted and/or the transmit powerchanges or transmit mode changes.)
 
   A reciprocalpath not only means equal path losses both ways, but also would be expected to haveequal path variability V and equal statistical skew or what I call “dB tilt” T both ways.   
 
Regardless of whether a path is reciprocal, the Variability and dBTilt formulas and values that I will describe have very appealing features. 
    --First, they cancel out all constant contributions to SNR and presumablyleave only statistics of the propagation path. 
    --Second, they only involve sums and differences of dB SNRs and attempt noaverages or fancy math like correlation. 
    --Third, they are flexible enough to contribute comparisons not only ofVariability and dB Tilt in different directions between a given pair of stations,but also such comparisons of different paths between different station pairs. 
    --Fourth, they permit comparisons of Variability and dB Tilt in different timeintervals (middle of night, wee hours of night) between a given pair ofstations. 
    --Fifth, they provide information that depends on collections of individual decodes, so the information is resilient tominor disturbances and differences in particular time instances when given pathconditions exist.  
   --Sixth, they arelargely independent of the number of decodes in each direction on a given path,or numbers of decodes obtained on different paths. (The decodes preferably number at least a couple dozen or more.)

In real-life operation of WSPR, thenumber of decodes and SNRs can differ greatly depending on WSPR transmit percentageTxPct and the strength of signal, which in turn depends on TX, RX, and antennasat each end.  Moreover, WSPR doesn't both transmit and receive in the same time slot. The Variabilityand Tilt statistics offer resilience and considerable independence from those path-unrelated factors.   
 
The next post shows the Variabilityand dB Tilt formulas and how to use them.