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TOPIC: Images of the Rx signal appears when NB1 is turned on

Images of the Rx signal appears when NB1 is turned on 11 Sep 2019 09:57 #1

  • VU3ESV
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I am facing a strange problem with NB1 in the latest version (1.3 RC1 and RC2) EESDR. Recently I tried to get rid of the strong noise signals appearing in the 20M band using the NB1. Earlier I was using the Timewave ANC-4 with a noise antenna, since the Tx power of Sunsdr is low (depending on the mode of choice) the ANC 4 refused to change to Tx mode. To my surprise the NB1 was able to get rid of the noise signals.

During the All Asian DX Contest, I have observed this strange behavior in the EESDR with the NB1 enabled. When a strong station is present in the band, I could copy the same station in 3 different frequencies, This issue initially noticed when I tried to work with the RJ4P @ 14.250. Signals strength was about S6 and I could not make a qso after many attempts, then I heard the same station @ 14.270Mhz with S9 level and had a qso. Then I tuned to 14.250 and 14.290 to check whether I am getting the same station on those frequencies or not. To my surprise , the same station is audible on both frequencies with S6-S7 level. I checked other strong stations in the band and experienced the same issue, I could copy them in 3 different frequencies with a 20 Khz difference.
When I disabled NB1, the issue mentioned above disappeared and the strong noise sources are back in the spectrum. Looks like the DSP for NB1 is creating images of the strong signals. In my case the string noise signals are appearing at every 20Khz interval in 20M band and the NB1 is able to block the same, but the images of the strong station appears at every 20 Khz interval, I am not sure whether this has any relation. I have reported this issue as a bug to EE, and expecting that some solution will be provided in the next releases.

I will try to attach some video recordings /screen shots of the issue.



Has anyone in this group faced similar problems with NB1? , I have seen comments like the NB1 is introducing the noise when it is switched on in the earlier version of EESDR.
Last Edit: 11 Sep 2019 10:00 by VU3ESV. Reason: adde another attchment
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