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

[Joe Subich, W4TV]

On 2022-05-18 10:51 AM, Kim Elmore wrote:

> 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.

I expect there is sufficient data available from the WSPR folks
(WSPRnet) for WSPR or from the RBN for CW.  While the signal
strength data is SNR and not purely dBm, in both cases you will
find a very well defined minimum SNR such that a 1 dB decrease
in signal level (or 1 dB increase in noise) will make the difference
between copy/response and "CQ in the face."  2 dB will *certainly*
make a significant difference.

The FT4/FT8 data from PSKReporter also includes signal (SNR) strength.

73,

    ... Joe, W4TV


On 2022-05-18 10:51 AM, Kim Elmore 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