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

[Chuck Dietz]

I am certain that, in a contest with over 1,000 contacts, one db would make
a noticeable difference. I seem to remember some tests like that, but I
agree it would be difficult to make valid comparisons.

Chuck W5PR

On Wed, May 18, 2022 at 10:07 AM Kim Elmore <cw_de_n5op at sbcglobal.net>
wrote:

> 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.
>
> On 5/17/2022 2:09 PM, Jim Brown wrote:
> > On 5/17/2022 11:54 AM, Wes wrote:
> >> The cost is about 40% less ($2.30/ft at Tessco) and the loss is only
> >> 1.7 dB @28MHz and proportionally less at 20 meters.  In fact on 20
> >> meters, you would be hard pressed to tell the difference.
> >
> > As a contester, I've experienced multiple situations when 1-2 dB band
> > the difference between a QSO and a CQ in my face.
> >
> > 73, Jim K9YC
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