TopBand: absorption and the s-word

[Carl K9LA]

Everyone,

The CCIR document that NM7M referred to is CCIR Report 252-2.  It is 
titled “CCIR Interim Method for Estimating Sky-Wave Field Strength and 
Transmission Loss at Frequencies Between the Approximate Limits of 2 and 
30 MHz.”  Whew!  That’s a mouthful.

What it does is present the method that IONCAP uses for estimating the 
median signal strength and the day-to-day variability (excess system 
loss) of the median value.  This excess system loss is presented in two 
tables: one for paths less than 2500km and one for paths greater than 
2500km.  Each table is sub-divided by season, geomagnetic latitude, and 
time of day (also included in this report are the tables for the 
day-to-day variation of the MUF about the median value - which is used to 
calculate the probability, called availability, that energy can get from 
Point A to Point B - which has nothing to do with signal strength as NM7M 
noted).

The absorption calculation (estimation is a better word) on page 92 of 
this report shows absorption to be directly proportional to SSN, and 
inversely proportional to frequency squared, elevation angle, and solar 
zenith angle.  Perhaps this is where the confusion lies - there is more 
absorption at the peak of a solar cycle, and the MUFs are higher at the 
peak of a solar cycle.  But as NM7M pointed out they do not necessarily 
track each other - they are two different processes at different rates - 
one in the D region and one in the F region.

And I’m glad to see that IV3PRK took the time to take a look at recent 
stratwarm data (regardless of the outcome).  I would hope that others, 
especially those who have contrary views, would test their observations 
with objective data.  I have the utmost respect for the observations of 
W8UVZ and KL7Y, but observations by themselves can be misleading if not 
challenged with objective data.

Carl K9LA

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