[Skimmertalk] Duplicate Spots

[Jeff Blaine]

Bob,

In the context of multiple antennas & skimmers, I'm curious about this 
data analysis use with skimmers.

Maybe it's been discussed before, but the RBN reports of the same 
station from the same skimmer vary quite a lot over time in my 
observation.  I've noticed this in many contests where I may have two 
screens of the RBN website feed up - one looking at my signal and 
another looking at another guy who I'm interested in comparing too, to 
see how we look at a single given skimmer site.  In this case, these 
reports can vary by 10+ db very easily, especially on the lower bands.

Why I'm thinking about that flows from your comment on the data analysis 
and it reminds me that I have seen some guys talking on the reflectors 
about using RBN reports for fine tuning antennas where they are 
considering changes that are in the few-dB range and using RBN as the 
measurement method.  I don't understand how that can be done with 
precision given the variability the atmosphere provides in cases 
excluding ground wave prop.  It seems like the noise in the data would 
swamp the relative compare value for this objective.

Skimmer reports SNR so both the noise floor skimmer sees as well as the 
signal(s) of interest needs to be stable over time so that Skimmer is 
able to provide a repeatable report (at least within a short measurement 
window).  Otherwise it seems like a guy would need to have two very 
different antennas (for example one skimmer tied to his TX vertical and 
another one tied to a low-noise directional RX) so that the SNR 
difference would be significant enough to overcome the prop.

Maybe there is a statistical method that addresses this? Or maybe I'm 
missing a key point here that is otherwise obvious?

73/jeff/ac0c
alpha-charlie-zero-charlie
www.ac0c.com

On 1/27/2025 1:21 PM, Bob Wilson, N6TV wrote:
> If you have two skimmer instances monitoring the same frequencies, 
> they should never post under the same Skimmer callsign, otherwise the 
> reports will be quite useless for data analysis, because the signal 
> reports will be bouncing all over the place and you can't tell which 
> report to use. Eliminating dupes alone doesn't solve this problem, 
> because the same station could be reporting with two different signal 
> strengths every few minutes, depending on which skimmer heard it first.
>
> If the two SDRs or two Skimmers are monitoring the same band segments, 
> use 3V8SS-1 for one and 3V8SS-2 for the other. You need to run two 
> independent copies of Aggregator to make this work right, since the 
> posted callsign is determined by the first SkimSrv.ini, not by Aggregator.
>
> For more details explaining how to do this, please review this post by 
> Aggregator author W3OA:
>
> https://groups.io/g/RBN-OPS/message/4938
>
> 73,
> Bob, N6TV
>
>
> On Sun, Jan 26, 2025 at 6:12 AM Ashraf Chaabane <ash.kf5eyy at gmail.com> 
> wrote:
>
>     Hi All,
>
>     I use two receivers with separate receiving antennas. Both are
>     skimming
>     to Aggregator. How can I ensure Aggregator doesn't send the same spot
>     twice if it happens that they come from both receivers?
>
>     73 Ash 3V8SS
>
>
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