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General Radio Discussion / Re: Propagation question
« on: December 25, 2016, 1526 UTC »
Although there are others here much more capable of answering the question, I'll take a crack at it. When Wolverine came on last night around 0200 UTC, the foF2(Maximum Usable Frequency) as reported by the Wallops Island ionosonde was hovering just below 3 Mhz. The hmf2 layer was bouncing around quite a bit, but was in the 300-350 km range (height). There is a formula on this link https://www.hfunderground.com/propagation/ that gives the Skip Zone for these foF2 and hmf2 figures as in the neighborhood of 900 miles. That means Wolverine's signal was skipping over listeners in a 900 mile radius from the xmtr location. It only means that the signal was going further out, so your location in Denver was outside the skip zone while for the rest of us, the signal was greatly attenuated. When Wolvie switched over to 4020 Khz, the figures for f0F2 and hmf2 from Wallops Island plugged into the formula yield a skip zone of roughly 350 miles. Therefore, the east coast and midwest received a much better signal because the signal was no longer bouncing over us. But the signal probably had to do a 2nd bounce to reach your location in Denver. Remember, it is the location of the xmtr and the MUF at that location that defines the Skip Zone. Not the location of the listener. When the band "goes long", it means the transmitted signal is returning to earth at a greater distance from the transmitter. I am using the Wallops Island ionosonde because it seems to be the closest one to my location here in Western Massachusetts. If I used another ionosonde from another location such as Alpena, Michigan or Boulder, Colorado....then the figures change for foF2 and hmf2 and the formula for the Skip Zone change accordingly. Not knowing the location of a given transmitter and therefore choosing the best ionosonde location makes the Skip Zone results a matter of speculation...I hope this makes some sense!
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S3 with UNID drama
