Hi Ben, You mentioned that you have two antennas. What kind antennas you have? Do they have any radiation patterns different from each other? What’s distance between the antennas? In any case you can affect to the noise level by combining two antennas that are at different locations. That beam forming generates nulls to the radiation pattern and those may attenuate less wanted signals at least in most directions. Result is improved S/N and so detection probability is higher. Another is issue is that there is less correlation of noise than signals in antennas in different locations or using different polarizations. In the best case the noise powers are added, but signal amplitudes are added and S/N improvement is 3 dB in ideal case. Well, signals from different directions may behave differently. As Chris noted one of the local noise sources may be even “nulled out”, sometimes with a considerable improvement in S/N.
73, Reino OH3mA From: Christopher Wawak via wsjt-devel [mailto:wsjt-devel@lists.sourceforge.net] Sent: Tuesday, December 5, 2023 1:15 PM To: WSJT software development <wsjt-devel@lists.sourceforge.net> Cc: Christopher Wawak <ch...@wawak.org> Subject: Re: [wsjt-devel] WSPR and Diversity Receive On Tue, Dec 5, 2023 at 3:35 AM Ben Gelb via wsjt-devel <wsjt-devel@lists.sourceforge.net <mailto:wsjt-devel@lists.sourceforge.net> > wrote: Have I actually improved the SNR substantially? Or is it possible I am just affecting the SNR calculation (I think it is roughly measuring the average noise level in the 2.5kHz window, and comparing to peaks) in a way that doesn't necessarily imply increased probability of decode? Hi Ben! I live in a suburban area with lots of RFI, and use a multiple receive antenna phasing system which effectively eliminates much of the local noise my antennas pick up. In my experience, only local signals are affected and anything further than the antennas' near field seems to remain the same. Based on this experience, is it possible that you're affecting near field noise which might increase or decrease the snr depending on whether the noise is being cancelled? I am not an expert, just trying to do some radio in a noisy environment! Hihi. KC2IEB Chris
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