Hi.
I always knew, that strong stations close to + or - 50 kHz from central is shown on the both sides of the waterfall/spectrum. I performed a test with a CW tone generator.
Generator freq is 21.200. When tuning to ~ 21.250 peak jumps to opposite side of the waterfall/spectrum and continue movement at least until? 25.262. The same behavior when tuning to opposite direction. So, when I tune my radio to 21.200 (for example), region (-50 ... -40) on the spectrum/waterfall shows me a sum of signals from 21.150 ... 21.160 (correct range) and from 21.250 ... 21.260 (incorrect range). Same for +40 ... +50 region.
I recorded a video -
On other bands the same (I checked 40m, 20m, 15m, 10m). Also, it's not related with the GUI app - I tested with R1CBU firmware.
The reason might be a not enough filtering signal before ADC, or something else.
My question is? how much devices has the same behavior?
If it very common - I'll exclude boundary regions (10 or 12 kHz) and scale remains data to full width on R1CBU FW. This way waterfall/spectrum with zoom level 1 will cover ~80 kHz, instead of 100kHz, but without annoying wrong signals.
73, Georgy // R2RFE
