[TowerTalk] Fw: Feeding single band HF yagis 500+ ft from the shack

[john at kk9a.com]

I do not know of any such study but I agree with K9YC that every bit
matters.  Certainly at some point having an extra 1dB of gain or 1dB less
loss becomes very expensive so everyone has to weigh how important it is to
them.  I'm sure that K3LR minimizes every fraction of a decibel of loss at
his station.

John KK9A - W4AAA 


Kim Elmore N5OP

I don't mistrust contesters that tell me they're certain of this, but... 
I'm wondering how they *know* that the difference is 1-2 dB on the 
*receiving* end? If they can increase the smoke by 1-2 dB and all of a 
sudden make the QSO, how do they *know* that's what did it? HF 
propagation is funny stuff. I do a LOT of statistics in my job as a 
research meteorologist/scientist, even though I'm not a formally trained 
statistician, and this is always my first question when presented with 
statements like this. Show me the data and how it was analyzed.

I'm pretty sure that there is no such data set in existence and I don't 
know of a good way to collect one. However, I suspect that the innate 
variability of ionospherically propagated HF signal strength is far 
larger than 1-2 dB and that any p-values we'd find at the 1-2 dB 
thresholds would be pretty large and so deemed statistically 
insignificant. I suspect there are too many degrees of freedom to ever 
pin this down.

I have no intention of starting a fight or creating discord. I *deeply* 
respect Jim's judgement and experience. Even so, I'd love to craft an 
experiment that would allow us to statistically determine the dB 
threshold that truly makes a difference on each band. While I'm 
spitballing, I might as well include different geomagnetic conditions as 
well.

That said, there's also a good argument for not wasting a dB if you can 
affordably avoid it.

73,

Kim N5OP.