On 8/1/2013 12:33 PM, David Gilbert wrote:
If I remember correctly, Dean Straw said that the ARRL crunched the
numbers back in the mid-90's using a computer that took a few days,
but I'm not sure it really matters. We're talking optimum
takeoff/arrival angles here, and I'm not sure that angle is a strong
function of F-layer densities. It would be pretty easy to check ...
just run a few paths in VOACAP for the same hour of the day using two
different SSNs and compare the TANGLE results for various
frequencies.
Although layer height varies, these layers are relatively thick. The
effective height of a layer at a given height varies with density which
is why we talk about refraction instead of reflections.
So antenna optimum antenna height does change withe the effective height
of the layer(s)
73
Roger (K8RI)
73, Dave AB7E
On 7/31/2013 8:42 PM, Roger wrote:
But is average really average. The sunspot cycles highs and lows
we have recently experienced are quite different than previous
cycles and so far this is reportedly, the lowest in a hundred
years. From what cycle are the averages taken, or is the
information updated to reflect current cycles?
I don't remember 40 ever being consistently as good for DX
throughout the nights as it was for 4 or 5 recent years.
73
Roger (K8RI)
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