# Tag Info

## Hot answers tagged signal-identification

9

I'm guessing many those signals are just noise. A fixed tone carries no information, so there would be no reason for a satellite (or anything else) to transmit it intentionally. The noise could be from an oscillator in some nearby electronics, or even from within the receiver itself. The noise may not even be at the frequency it appears in the waterfall: ...

7

There is a range of possibilities, depending on what kind of signal you want to find. I'll start from easy and move up to hard. I'm assuming that you are using an FFT to get your spectra. RFI. An earlier poster referenced some papers on finding RFI. I don't know precisely how that is defined, but lets assume that it is unintentional RF from things like ...

7

It's probably an ionosonde — sending out HF radio signals not to communicate but to measure the reflections and thereby determine the current characteristics of the ionosphere. The signal is probably not actually a series of brief transmissions, but a continuous chirp transmission with continuously increasing frequency. Two reasons: As far as I know, this ...

6

If you zoom in on these signals, there are labels describing what the stations are. Example, many of the signals around 20kHz are military: If you mouse over the labels, it will expand them. You can zoom with the mouse wheel or with the controls in the "Waterfall view" section.

6

Yes, you'll have to look at it. I can't go into detail about every possible modulation, because there's just too many. But typically, a look at the spectral representation gives you an idea of whether you're dealing with a straightforward single-carrier signal a spread-spectrum signal or a multicarrier signal. One place to see some examples is the Signal ...

5

These are data transmissions using OFDM. They are government or military point to point data links. I would expect that the data would be encrypted.

5

The fact that they align properly to the FT8 15-second period, and have 8 tones (the same as FT8) is a sign that these may be distorted FT8 signals, caused by AF harmonics in the transmitter or the receiver. The one on the right, being about 100Hz wide, is a second harmonic, and the one on the left, being about 150Hz wide, may be a third harmonic. But ...

5

If I read the instrumentation correctly, this is but 20 kHz; that's pretty wide for what I'd expect for Ham operation on HF. It's not "very wide" per se. (I'd define "wide" based on the ratio of bandwidth to center frequency, and that's but 0.2% here.) This looks a bit like an OFDM signal, especially with the hints of side lobes. 20 kHz OFDM in HF sounds a ...

4

After catching it again today, at 19:30 BST on 5.90mhz I looked it up on shortwaveschedule. It seems to be the lead-in call for Radio Romania International. Mystery solved. The introductory music & beacon can also be heard on this old recorded broadcast from 2011.

4

If nobody is able to recognize what kind of signal you're dealing with by looking at your waterfall screen shots, then perhaps your best chance of identifying the signal would be to use old-fashioned RDF (radio direction-finding) techniques. If you can, consider borrowing a portable battery-powered receiver that can do 40m, and ideally also SSB, like a ...

3

Well, this is a well-studied field (Radio Frequency Interference detection and mitigation). There are tons of literature about it. The noise you receive is theoretically Additive White Gaussian Noise (AWGN). That means that its Probability Density Function (PDF) is Gaussian, and the pdf of its samples' power is exponential. By setting a false alarm ...

3

Both marked signals follow an 8 tone MFSK pattern. The one on the left is about 125 hertz wide while the one on the right is about 100 hertz wide. The signal on the left appears to follow the waterfall that would be expected from an Olivia 8/125 (8 tones with 125 hertz bandwidth) signal although this is not a common Olivia mode. Olivia is a free typing, ...

3

display_qt is a GNU Radio example program. It does not display any actually existing electromagnetic signal but internally generates a 1500 Hz sinusoid. The code creates a sine source and a noise source, // Source will be sine wave in noise src0 = analog::sig_source_f::make(rate, analog::GR_SIN_WAVE, 1500, 1); src1 = analog::noise_source_f::make(analog::...

3

Could very well be someone who is bored and opens the repeater without actually transmitting anything useful. Happens on a lot of repeaters. You only need one person to do this to bother all users of the relay...

3

From the wide spectrum screenshot it's evident your receiver is seriously overloaded. Note: the signal around 445.982 which appears to be identical other than being "flipped", and a little stronger. This comes from IQ imbalance in the receiver. additional copies of the signal all over the place. These are caused by intermodulation and harmonic ...

3

Transmission between antennas is "two port in to two port out". But: in between there is a transmission path with reflections. Some frequencies are attenuated and some other frequencies are even stronger than average. That is called Rayleigh path (sorry, not complete for the moment). The transfer is frequency-dependent AND antenna position ...

3

There's multiple way that multiple signals can be sent at the same time on the same frequency. One is to have multiple antennas, where even though the antennas themselves can be omnidirectional, they can be used to "beam form" by carefully offsetting the signal. And likewise the receiver can do this trick. Also see this article on MIMO. Wifi can ...

3

You have to provide the -i option to invert the signal in order to decode it properly. The lowpass filter is not really required as this is a quite strong signal (but does not harm either). $./rs41ptu -i --crc -vx wav/20140717_402MHz.wav sample_rate: 48000 bits : 8 channels : 1 samples/bit: 10.00 [ 5047] (K1930308) Do 2014-07-17 12:32:13.999 lat: ... 3 If you approximate the yellow trace as a rectangular function: $$\text{rect}(ax)$$ then the Fourier transform of this is: $${1 \over |a|} \cdot \text{sinc}\left(\xi \over a\right )$$ Of course, a lightning impulse isn't exactly a rectangular pulse, but I suspect that does not substantially change the character of the frequency response: infinite, with ... 2 LED and CFL lights are a known nuisance to hams. It could possibly be one or some equally non-EMC conscious electronics. http://www.ukqrm.org.uk/lighting.php 2 One possibility is Digital Radio Mondale (DRM), but given that it's only five seconds long each time - exactly - I'm not sure. It does consume the same 10kHz bandwidth, and has some pattern similarities. Here's one resource for visual signal identification: http://www.rtl-sdr.com/signal-identification-guide/ Digital modes are given a pretty thorough ... 2 If you can record a waterfall plot of the signal (the easiest way is via a cheap sub$20 RTL-SDR dongles, as @user3431540 mentions), you might have some luck identifying the signal visually via the brilliant Signal Identification Wiki. Here for example is a waterfall plot for APRS: In fact, some software may even allow you to create waterfall plots from ...

2

If you're purely interested in 2.4GHz Wi-Fi signals then I can recommend the free Ekahau Wifi Heatmapper for Windows. http://www.ekahau.com/wifidesign/ekahau-heatmapper Of course this doesn't pick up any non-802.11 signals but may still be of great help. Heatmapper doesn't support GPS in the free version but if you have a floor plan then you just walk ...

2

Is there a gadget that can identify the different RF signals in a noisy environment? Not in general. One radio's signal is another radio's noise, especially in the case of high-bandwidth digital signals. The problem is essentially the same as wanting one radio to receive every type of signal in the environment. Which is theoretically possible (as long as ...

2

Been probing around in your signal. The longer "blips" definitely start with a tone (... with a region where phase is a linear function of time), but then it looks rather random. So, likely, a PSK system with some constant tone preamble? My quick & dirty analysis tool here is Miek's inspectrum You'll need to convert your wav back to 32bit ...

2

I also didn't notice that box before, but it has the date as well, 2017-01-08 in it(YMD), a Sunday. The center is 10.130, and at S7 that's fairly strong. Also I think the actual signal is 26khz wide with the 3khz side lobes. I don't think its DX. At 9am the sun is well up, the ionosphere E layer has merged back into D. There would be no grey line ...

2

Welcome the land of QRM also known as man made noise. I realize this came from the headphone jack, so it recorded as stereo. its really a mono signal, both channels have the same wave form. because you used a lossy compression it would be may make it harder to try and decode it. (not that I'm that good mind you) It kind of sounds like a problem we had here ...

2

A Wi-Fi transmitter, like a lightbulb, throws out photons in a lot of directions. Only some of them will be captured by the receiver. Most will go elsewhere, eventually being absorbed by walls, atmospheric water vapor, and so on to be converted to heat. The Friis transmission equation explains this in more rigorous terms. Even if the two antennas are ...

1

"A" appears to be T10, a mode available on the JTDX app. I believe "B" is simply an artifact from one of the over-driven FT8 signals on the band. No doubt I'll be corrected if I'm wrong :) 73 Dave - KB3MOW

1

I copied a test transmission from H.A.A.R.P. on this frequency in the 1990s. It was on 6.99 MHz @ 0430 - 0435 UTC. I have a card from them 3/8/97 confirming my reception. Perhaps that's what it is.

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