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

[Lux, Jim]

On 5/18/22 8:34 AM, Joe Subich, W4TV wrote:
>
> 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 


The challenge with SNR data (as opposed to absolute levels) is that you 
don't know whether the N is propagating over the same path as the S, or 
different. A great propagation path doesn't help if you and the noise 
being generated in your area propagate by the same path.

But you might be able to normalize it somehow. I spent the better part 
of a year trying to come up with a good worldwide atmospheric noise 
model, trying to merge lightning data, ITU curves, etc. - There just 
aren't the public data sets readily available to figure it out. It 
doesn't help that space observations are above the ionosphere, which 
blocks a lot of the "interesting" frequencies for hams.


I've long maintained that the advantage of gain antennas (Yagis, 4 
squares, etc) is more the ability to place a null (or other wise reduce 
the strength) of interfering sources, whether natural or man-made.  
Pointing the fairly wide beam of a Yagi off the great circle heading to 
the desired other end reduces the desired signal, but reduces the 
undesired signal even more, because the gain vs azimuth curve has an 
increasingly steep slope as you move off the boresight.