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Software / Re: directKiwi project
« on: June 04, 2018, 0555 UTC »
Hi Linkz,
I noted the addition of microkiwi_waterfall.py to Christoph's kiwiclient.git which indeed takes a snapshot of a specified host kiwi. With default arguments it shows the calculation result over the whole 30 Mhz range but can be narrowed to a high zoomlevel. Locally I use it for manually selecting a suitable antenna for a chunk of the spectrum. This "global" SNR gives a pretty good indication for SNR at a certain kiwi like Marco shows at http://sibamanna.duckdns.org/sdr_map.html.
Another indication of SNR could be the dB value of signal mean over standard deviation just for the passband. The idea of suggesting a measure of SNR is an attempt to avoid kiwis with high RSSI readings due high local QRN or QRM end up on top of the list.
As you mentioned for voice signals within the passband of the selected mode it remains to be seen if there is any benefit of having such an SNR measure. Probably best way to find out is to plot this together with RSSI in a real time graph.
To go a step further I guess for digital signals measured BER would be a better qualifier. For speech SNR is not well defined since the power spectral density of a voice signal is highly variable with time and almost as random as the noise itself. There are routines trying to separate speech from noise first such as using VAD (voice activity detection) or syllabic rate detection and then estimate SNR. However this is probably overkill for the present project.
Anyway thank you for coming back to my suggestions and a filter for to exclude the worst remotes will already be a good addition.
Best regards, Ben.
I noted the addition of microkiwi_waterfall.py to Christoph's kiwiclient.git which indeed takes a snapshot of a specified host kiwi. With default arguments it shows the calculation result over the whole 30 Mhz range but can be narrowed to a high zoomlevel. Locally I use it for manually selecting a suitable antenna for a chunk of the spectrum. This "global" SNR gives a pretty good indication for SNR at a certain kiwi like Marco shows at http://sibamanna.duckdns.org/sdr_map.html.
Another indication of SNR could be the dB value of signal mean over standard deviation just for the passband. The idea of suggesting a measure of SNR is an attempt to avoid kiwis with high RSSI readings due high local QRN or QRM end up on top of the list.
As you mentioned for voice signals within the passband of the selected mode it remains to be seen if there is any benefit of having such an SNR measure. Probably best way to find out is to plot this together with RSSI in a real time graph.
To go a step further I guess for digital signals measured BER would be a better qualifier. For speech SNR is not well defined since the power spectral density of a voice signal is highly variable with time and almost as random as the noise itself. There are routines trying to separate speech from noise first such as using VAD (voice activity detection) or syllabic rate detection and then estimate SNR. However this is probably overkill for the present project.
Anyway thank you for coming back to my suggestions and a filter for to exclude the worst remotes will already be a good addition.
Best regards, Ben.