Unexplained noise on several bands

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KC4LZN
Posts: 32
Joined: Fri Oct 09, 2020 2:23 pm

Unexplained noise on several bands

Postby KC4LZN » Tue Feb 07, 2023 10:58 am

Sometimes when shifting modes and/or bands, I'm seeing this noise. There is no rhyme or reason to it and seems to affect 30 meters the worst. I have not seen it above 15 meters. When noted, I simply turn Thetis off and then back on, problem goes away.

Is this a corrupt database and need to rebuild or is there a hardware concern? I don't power cycle the hardware but have in the past. It has cleared without power cycling the hardware.

Pictures attached of before with noise and then after, this particular shot on FT8 30 meters. They were taken at different times hence the difference in the amount of traffic noted on the spectrum.

Screenshot_20230206-045228_4.png
Screenshot_20230206-045228_4.png (869.72 KiB) Viewed 1033 times


Screenshot_20230206-081808_2.png
Screenshot_20230206-081808_2.png (632.51 KiB) Viewed 1033 times


73 John
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w-u-2-o
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Joined: Fri Mar 10, 2017 1:47 pm

Re: Unexplained noise on several bands

Postby w-u-2-o » Tue Feb 07, 2023 1:58 pm

KC4LZN wrote:Sometimes when shifting modes and/or bands, I'm seeing this noise. There is no rhyme or reason to it and seems to affect 30 meters the worst. I have not seen it above 15 meters. When noted, I simply turn Thetis off and then back on, problem goes away.

You are showing your WSJT-X spectral display. Does the noise also appear in the Thetis spectral display? If not, then focus should shift to the VAC setup.
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KC4LZN
Posts: 32
Joined: Fri Oct 09, 2020 2:23 pm

Re: Unexplained noise on several bands

Postby KC4LZN » Tue Feb 07, 2023 2:07 pm

w-u-2-o wrote:You are showing your WSJT-X spectral display. Does the noise also appear in the Thetis spectral display? If not, then focus should shift to the VAC setup.


Scott,

I believe it does.

If and when it occurs again, I'll get a snap of the Thetis spectrum.

73
John
w9mdb
Posts: 446
Joined: Sun Apr 09, 2017 5:53 pm

Re: Unexplained noise on several bands

Postby w9mdb » Tue Feb 07, 2023 2:37 pm

It's at 50Hz intervals so I suspect some 50Hz power supply noise -- couldn't be too far away...you'd have to hunt it down with
https://electronics.stackexchange.com/q ... oises-from

You can do some inside-the-house hunting with an AM radio.
https://www.youtube.com/watch?v=lXPJvSU8MwI
https://www.youtube.com/watch?v=NibgLgYiQtU

LED lights are known to cause such problems.
https://www.youtube.com/watch?v=zUgCM6cCUj0

ARRL links...
https://www.arrl.org/radio-frequency-interference-rfi

Mike W9MDB
Mike W9MDB
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w9ac
Posts: 290
Joined: Sun Apr 09, 2017 4:01 pm

Re: Unexplained noise on several bands

Postby w9ac » Tue Feb 07, 2023 2:56 pm

See the post below from 2017. I once had a similar issue when using an early version of Thetis. It could be completely unrelated, but I think it's worth investigating Ethernet port grounding and quality of Ethernet cabling, especially if you're using a multiport Ethernet switch:

https://community.apache-labs.com/viewtopic.php?f=22&t=2401&p=2669&hilit=w9ac+ethernet#p2669

Paul, W9AC

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