Rising noise floor at tuned frequency?

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technodruid
Posts: 1
Joined: Thu Dec 12, 2019 2:38 am

Rising noise floor at tuned frequency?

Post by technodruid » Thu Dec 12, 2019 2:42 am

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.
Attachments
1.jpg
the noise floor rises up to the tuned frequency, then falls down symmetrically.
1.jpg (364.93 KiB) Viewed 2496 times

tim_rtd
Posts: 155
Joined: Fri Jun 30, 2017 11:34 am

Re: Rising noise floor at tuned frequency?

Post by tim_rtd » Thu Dec 12, 2019 2:10 pm

Try clicking that Correct IQ button.

rtlsdrblog
Site Admin
Posts: 2770
Joined: Mon Nov 19, 2012 11:54 pm

Re: Rising noise floor at tuned frequency?

Post by rtlsdrblog » Fri Dec 13, 2019 6:16 am

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.

qrp
Posts: 50
Joined: Wed May 22, 2019 11:16 pm

Re: Rising noise floor at tuned frequency?

Post by qrp » Fri Dec 13, 2019 2:28 pm

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)

tim_rtd
Posts: 155
Joined: Fri Jun 30, 2017 11:34 am

Re: Rising noise floor at tuned frequency?

Post by tim_rtd » Sat Dec 14, 2019 2:48 pm

Yes, but I typed correct, not swap.

rtlsdrblog
Site Admin
Posts: 2770
Joined: Mon Nov 19, 2012 11:54 pm

Re: Rising noise floor at tuned frequency?

Post by rtlsdrblog » Sun Dec 15, 2019 8:02 am

Correct IQ won't do anything for the hump present with E4000 dongles, what he needs is the offset tuning button.

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