Mancow, can you explain the purpose of the Hysteresis setting and how it relates to the SNR setting? The website for this plugin shows apparently an older version, and there's no Hysteresis setting in his example.
BTW I am am also using SDR# with AirSpy, and the best I can get for the entire 225 to 400 band is around 12 to 15 seconds.
The SNR level (top red line) is the minimum signal level, above the noise floor, that will trigger a 'hit' and stop the scan/search. I usually set mine for 17-20dB (above the noise floor) in SDR#. Too much lower and you will get false hits on unwanted spurs in the noise floor.
The Hysteresis (lower red line) is the level in dB below the above SNR level that the scanner will remain on the 'hit' frequency after stopping. The Hysteresis is there to allow for a degree of signal fade during monitoring, such as when a station is mobile or when subject to mutipath fading etc. I usually set this to about 10dB below the SNR level when monitoring really weak signals. If you set the Hysteresis level too low, the scanner will never re-start after the signal disappears, as the spurs in the noise floor will keep triggering it.
Other points:
*
Don't use the 'Auto gain' setting in the SDR receiver hardware. Manually setting the gain for the band you are operating on always produces the best S/n, lowest alias's and best weak signal performance. Find a weak signal and manually adjust your gain to produce the best S/n. For example, on the SDRPlay, I manually set the gain to 40. On an RTL dongle, I set both the IF and Mixer gain to 4 or 5 and crank the LNA/RF gain to max or 15 (from memory).
* Match the frequency step with the service you are monitoring i.e 12.5Khz, 25Khz, 50Khz etc.
* Reduce to a minimum your noise floor, by using a good external antenna, away from noise sources in your shack.
* Many of the receivers, including SDRPlay will suffer from FM broadcast signal alias's on the 220-400Mhz band when using a broadband external antenna. Use an FM trap if required.
Once setup correctly and optimized, you will be blown away by how quickly you can scan a huge slap of spectrum.
