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Rising noise floor at tuned frequency?

Posted: Thu Dec 12, 2019 2:42 am
by technodruid
Hi,

Just unboxed my Noolec NESDR SMArt XTR yesterday, so I am very new to this.

I have a weird "rising" noise floor at any tuned frequency. Is this normal? It appears to be present at all frequencies, all antennas included with the ham it up kit, including a wire antenna with the 9:1 balun.

Re: Rising noise floor at tuned frequency?

Posted: Thu Dec 12, 2019 2:10 pm
by tim_rtd
Try clicking that Correct IQ button.

Re: Rising noise floor at tuned frequency?

Posted: Fri Dec 13, 2019 6:16 am
by rtlsdrblog
The XTR is an E4000 based dongle. Those aren't the best and the R820T2 is usually considered as better, but it does have the advantage of the higher frequency range.

That middle spike is something that is expected with E4000 dongles. To get rid of it you can choose "Offset Tuning" in the RTL-SDR settings.

Re: Rising noise floor at tuned frequency?

Posted: Fri Dec 13, 2019 2:28 pm
by qrp
tim_rtd wrote:
Thu Dec 12, 2019 2:10 pm
Try clicking that Correct IQ button.
swap I/Q cannot help with noise floor, it just mirrors frequencies around DC (LO frequency)

Re: Rising noise floor at tuned frequency?

Posted: Sat Dec 14, 2019 2:48 pm
by tim_rtd
Yes, but I typed correct, not swap.

Re: Rising noise floor at tuned frequency?

Posted: Sun Dec 15, 2019 8:02 am
by rtlsdrblog
Correct IQ won't do anything for the hump present with E4000 dongles, what he needs is the offset tuning button.