Monitor and detect RF signals over a longer period of time

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Duncan1234
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Joined: Wed Nov 28, 2018 2:00 pm

Monitor and detect RF signals over a longer period of time

Post by Duncan1234 » Wed Nov 28, 2018 2:07 pm

I am looking for an SDR (HackRF should work) and a software that can monitor a wide range of frequencies.
It will be used in a shielded space, to monitor if a device "leek" or sending unwanted signals.
The device should be able to monitor the shielded space for a longer period of time (several days) and the user should be able to get "reports" from the software. looking something like: Have RF been detected? when was it detected? how strong was the signal? and what frequency? (knowing the exact frequency is not super important) So that the user don't have to sit by the screen for several days and watch.

I hope you understand what i mean, does anybody know of a solution that can help me?

rtlsdrblog
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Re: Monitor and detect RF signals over a longer period of time

Post by rtlsdrblog » Thu Nov 29, 2018 11:07 am

If the bandwidth you want to monitor is 20 MHz, the HackRF will work. Any larger bandwidth and you'll need to jump and scan quickly, and that could result in fast pulse signals being not detected.

In terms of software, I would simply use the HackRF equivalent of rtl_power to log frequency strength data, and then generate a waterfall graph at the end of the day, or every few hours. Then you could visually look for signals that where transmitted, and easily determine how long they were transmitting for.

Username
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Re: Monitor and detect RF signals over a longer period of time

Post by Username » Thu Nov 29, 2018 7:11 pm

Please note it take A LOT of CPU, Grafik Power!

Duncan1234
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Re: Monitor and detect RF signals over a longer period of time

Post by Duncan1234 » Wed Dec 05, 2018 3:57 pm

Thanks for the answers.
But, if i don't care about the specific frequency, would that be more easy?
For example: i have this really simple sweeper that has 4 diodes that starts to blink when it detects a signal, and the stronger the signal the more it blinks. i bet you all know the tool.
A similar tool could work, but it must have the ability stand alone for a long period of time and only record the timestamps and straights of the signals detected.

Username
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Re: Monitor and detect RF signals over a longer period of time

Post by Username » Wed Dec 05, 2018 4:02 pm

SDR# and a Laptop?!
You need to tune that device. I dont know where you life but here a lot of strong sigales in the Air!

Duncan1234
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Re: Monitor and detect RF signals over a longer period of time

Post by Duncan1234 » Wed Dec 05, 2018 8:15 pm

yes, but i will be using a shielded space. a farady cage. so no interference.

dz93
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Re: Monitor and detect RF signals over a longer period of time

Post by dz93 » Thu Dec 06, 2018 6:26 pm

Duncan,
Unless you're able to dig through github to find a software already built to do what you're talking about, you may either need to build it yourself or figure out something different. My suggestion to start out with is maybe run a spectrum analyzer that will output the waterfall to an image file. This way you can look back over the bandwidth monitored to see any changes over time. Then from that determine what frequency the signal was on, how strong, etc. Do you have any experience with GNU Radio Companion? You may be able to build what you want using GRC. As others have mentioned, though, with a hackRF you will only get 20MSPS max. LimeSDR can do around 50MSPS. Any higher than that and you'll want to look at an Ettus product.

rtlsdrblog
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Re: Monitor and detect RF signals over a longer period of time

Post by rtlsdrblog » Thu Dec 06, 2018 11:20 pm

Duncan1234 wrote:
Wed Dec 05, 2018 3:57 pm
Thanks for the answers.
But, if i don't care about the specific frequency, would that be more easy?
For example: i have this really simple sweeper that has 4 diodes that starts to blink when it detects a signal, and the stronger the signal the more it blinks. i bet you all know the tool.
A similar tool could work, but it must have the ability stand alone for a long period of time and only record the timestamps and straights of the signals detected.
The SDR still has to tune through the spectrum to get the signal strength data, it can't receive the entire bandwidth at once. Those wideband analog power meters do what you want, but IMO it's pretty useless if you don't know the frequency of the powerful signal.

snn47
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Re: Monitor and detect RF signals over a longer period of time

Post by snn47 » Sat Dec 08, 2018 7:15 am

Unless we have an idea of what type of signals you want to detect/monitor it is hard to advise.

Which senitivity do you need? For all detector-sensor, SDR or Spectrum analyzer, the achieveable bandwith is limited.

Which dynamic range do you need between weakest and strongest signal is radiated by the device you want to observe .

How is the duration of the signals and what is their occurance?

Are the signals distributed in such a way over a frequency range (spread spectrum) that a rceiver has to remain a certain time on a frequency before it can detect it?

What frequency (range) are you looking for?

Therefore what type of pickup sensor/antenna do you want to use for detecting you only spoke of receiving? Is it broadband enough, if not you may detect nothing, even though signals are present, at the frequency (range) you are interested in.

Even the best shielded space have limits to the isolatation they can achieve. Comercial jackies (boxes/rooms) degrade everytime you open them. Even a small piece of paper in between the contacts reduces the shieling considerably. Once you have a feedthrough for cables, power or data cable, some outside radiation will leak into the shielded space, if you have an active device(s) you have additional sources. The required shielding depends on how weak the signals you want to detect are, but you can establish this without the device under test beeing active.

There is a reason why comercial setups for detecting leakage radiation and out of band emissions are not cheap to perform.

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