Questions tagged [software-defined-radio]

Radio devices that use digital signal processing in place of analog electronic components to manipulate RF signals.

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Would it be possible for a software-defined FM receiver to demodulate two signals on the same frequency?

When two FM signals are transmitted on the same (or about the same) center frequency, either you hear only one or you hear that noise I'm sure most of you have heard. Would it be possible for a ...
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1 answer
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Sine wave 'frequency' in recorded signals

I'm trying to replicate a signal from a remote using another wireless transmitter (a cc1101 to be exact). I got somewhere, but I am stuck, and have a fundamental question At the top is the signal I'm ...
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2 votes
0 answers
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What could cause an IQ diagram to shapeshift randomly?

I'm trying to interface a DVB-S2 transmitter to a DVB-S2 demodulator - for now with a direct cable+attenuator link. Both are set up exactly with the same parameters (same carrier frequency [2150MHz], ...
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0 votes
2 answers
115 views

Does the specific frequency of a CW tone make a difference to output from a practical SDR?

I'm using a Nuand BladeRF 2.0 micro, which is based on the AD9361. I'm just trying to get a handle for how it behaves at the moment, so I was testing generation of some CW tones using GNU Radio and ...
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1 answer
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How to use SDR equipment and Gnuraio record `time domain` data?

From answer, A comment has pointed out that one could think of the saved data as in the time domain under some circumstances because it is literally series of 32-bit values written as fast as ...
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3 votes
2 answers
477 views

SDR Transceiver over LAN

The feed line is a limiting factor when designing a home HAM system. The further the antenna is placed from the transceiver, the greater the cost and attenuation. Is there a way to solve this with ...
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0 votes
1 answer
34 views

How to use RF Input B ports in GNU radio?

I have an Ettus B210, which has 4 ports: RF Input A: RX/TX and RX2, and RF Input B: RX2 and RX/TX. In GNU Radio using the USRP block I can use both ports of RF Input A. But I don't succeed to use the ...
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1 answer
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Is it possible to use LimeSDR/HackRF with DireWolf?

I was wondering if one could use DireWolf with the LimeSDR/LimeSDR Mini/HackRF. The bandwidth would be much more acceptable than even the highest rate sound cards, which rarely reach even 192 khz. Can ...
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0 answers
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Real time half duplex with two hackrf one on gnuradio

I would like to know the possibilities to make a clear real time half duplex communication between two hackrf one, being both running on gnuradio. I would like to use on both ways: By a sync call on ...
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0 votes
1 answer
120 views

Identifying the signal picked up at 363mhz with sdr++. It is from Burmese military's communication. I want to know what it is and how to decode it

As shown in the picture, I want to identify the signal and how can I decode it, please. Here is the link to audio.wav file: https://u.pcloud.link/publink/show?code=XZRoY5VZggSdx8NPqKp3hAOaphcsKVVCqrik
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0 votes
1 answer
99 views

Why does my transmitter spam the SDR waterfall with this strange pattern?

I was recently playing with a combination of SDR and a Baofeng using two separate antennas and I noticed something strange when I transmit using the Baofeng: I heard that it's normal to observe ...
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2 votes
1 answer
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Why would a VNA not make a good Spectrum Analyzer? Or an SDR a good VNA?

Happy to be corrected where I'm wrong in any of this but in broad strokes my understanding is: Spectrum Analyzer measures input signal strength while sweeping across frequencies, measuring RF ...
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0 votes
1 answer
78 views

Is Gnuradio `file sink` data time domain data or frequency domain data?

When I enable file sink,I could save and read data of Gnuradio as below: Questions as below: 1.Is the file sink data time ...
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1 vote
1 answer
121 views

detecting transmissions around the house

A few years ago I bought an SDR and installed it on my home security system. While I was playing around with it I discovered a program or something that allowed me to see the transmissions from three ...
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-2 votes
1 answer
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How to know whether aliasing occurs when observe unknown signal?

Per my good but downvote question,I am hard to set sample rate even to a standard cosine wave. When I observe unkwon signal,how to judge whether aliasing occurs?
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-3 votes
1 answer
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GNU Radio does not work expectedly when the frequency is 2x the sample rate

Simple flow in GNU Radio 3.8.2.0 (Python 3.9.2). If samp rate is 32k, when Frequency moves to 64k the recovered ...
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1 answer
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Help synchronize on unknown frequency sequence

I am having trouble to synchronize on a frequency hopping pattern between an emitter Tx and a receiver Rx. More precisely, the ...
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0 votes
2 answers
29 views

Is number of items in`file sink` integer multiple of `sample rate`?

I use flow graph for file sink as below: When I stop running this flow graph, there are 110000 float numbers in file ...
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-1 votes
1 answer
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What's the usage of `Multiply Const 1` and `Multiply Const 0`?

Based on Gnuradio, Multiplies the input stream by a scalar or vector constant (element-wise if vector). output = input * constant In above web page, I found ...
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0 votes
1 answer
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what's the usage and benefit of segments in Gnuraio `file meta sink`?

In Gnuradio website, Max Seg. size is Length of a single segment before the header is repeated (in items) At first,I think ...
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1 vote
1 answer
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Are there major advantages to using DVB-S2 vs CCSDS (or vice-versa)?

In Cubesats, DVB-S2 and CCSDS are both equally present as communications standards. Are there really any pros and cons, that is - a "best choice for a given application", or are they just ...
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0 votes
1 answer
64 views

How to set external clock of `--device-settings` in soapy_power?

External pps equipment connected with USRP. In soapy_power,I set --device-settings 'clock_source=external' but failed. ...
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0 answers
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Why can't I get the radio/waterfall to show in SDRAngel - GQRX works fine

I was wondering why the digital decoder in SDRAngel wasn't working, but now I see that even broadcast FM isn't showing a bump in the spectrum: I can play broadcast fm radio stations (the ones playing ...
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2 votes
0 answers
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Why the Receiver Sensitivity theoretical value doesn't match its experimental value when using USRP B200mini in GNU Radio?

I'm using a USRP B200mini SDR card for my GNU Radio energy detector project. I wanted to measure its Receiver Sensitivity ($RS$) experimentally and compare the experimental value to the theoretical ...
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1 vote
3 answers
116 views

What can be used to protect an SDR receiver against bursts?

I am using a USRP B205 to detect electromagnetic pulses. Sometimes the signal power bursts to 100 dB, average power is around 10 dB. What can be used to protect the SDR receiver against bursts?
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-1 votes
1 answer
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What's the negative float of rtl_power output means?

I got below float numbers after soapy_power -f 80M:100M -B 1000 --output a --format rtl_power: ...
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1 vote
1 answer
108 views

AM radio cross-talk / hearing strong station everywhere

I've built the M0AYF active loop antenna for my RTL-SDR, using BC847C for the amplifier transistors. There are a couple very strong AM stations here, usually playing music. What I'm noticing is that ...
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2 votes
2 answers
110 views

What's the difference between LPF and BPF in context of bandwidth setting?

I'm used to simple RX/TX bandwidth configurations, on my VHF FM rig it's either narrow, normal, or wide. It seems to be much more complex on my new HF SDR rig, and the instructions don't say anything ...
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3 votes
4 answers
833 views

Why am I hearing FM radio show content on 1.355 MHz? (Using CubicSDR and SDR kit)

I am just beginning to learn about SDR. I purchased a "NooElec NESDR Mini 2 SDR & DVB-T USB Stick (RTL2832 + R820T2) with Antenna and Remote Control" I plugged it into my Mac, downloaded ...
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7 votes
6 answers
7k views

Why is 20m band waterfall showing signals every 50 kHz?

I'm very new to shortwave listening and just got to grips with my RTL SDR HF dongle. Last night while on the 20m band, there were signals exactly every 50kHz, starting exactly at 14.000MHz, then at 14....
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1 vote
1 answer
99 views

USRP-B210 GPSDO will not lock

Hi I own a b210 and I have a gpsdo that's installed but i do not have the antenna yet. Can I use it as a 10mhz reference and pps until I obtain the antenna?
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2 votes
3 answers
122 views

What cause the shape of frequency spectrum convex or concave?

I use gnuradio and fosphor to view the spectrum from USRP B210, default gain set to 34, output looks like concave as below: ...
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0 votes
1 answer
67 views

Does signal frequency affect the band width of SDR hardware?

I am new to SDR,already owned USRP B210 and start to learn Gnuradio. I have follow question: B210 has max bind width 56Mhz.When I use max sample rate to received signal,does the signal frequency(...
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1 vote
2 answers
59 views

What's the `Minimum signal duration` and `Minimum detectable signal duraion` of Ettus B210?

When read keysight 9913A manual, Minimum signal duration with 100% probability of intercept (POI) at full amplitude accuracy 12 µs Minimum detectable signal 22 ns What's the ...
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0 votes
1 answer
56 views

How a reply system works on a aircraft transponder? [closed]

I'm trying to build a transponder ramp test for mode c and s of aircrafts for my degree. I have a problem, I didn't understand reply system of transponde, how can I doba reply of a signal to test one?
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0 votes
2 answers
411 views

Antenna suggestions for SDRPlay RSP1A

Looking for suggestions for a portable antenna for use with a SDRPlay RSP1A. I notice that most other SDRs come with a few antennas, but not the RSP1A. I have a 2m/70cm HT, so I own a Nagoya NA-771R ...
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0 votes
2 answers
109 views

human voice / music radio signal without RF moduation

This question is about digital voice modes that are used with AM / SSB / FM radios. Dstar , FreeDV , etc. assumptions: pulse width modulation amplifiers can take a digital signal as input. a software ...
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9 votes
5 answers
801 views

What limits a PIN diode or varicap from being used in a "Software Defined [Radio] Filter"?

A PIN diode varies its capacitance based on a DC bias, and a Varicap exhibits this effect even more clearly. What limits the use of "solid state variable capacitors" like these for ...
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0 votes
1 answer
239 views

Modify a CB radio to connect to a wireless network? [closed]

Is it possible to modify a CB radio to connect to a wireless network, and potentially send any data sent from the radio as a buffer to an outside source like an API? If so, what would be the best way ...
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0 votes
1 answer
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How to get the "real" number of samples coming in an sdr

so I am fairly new to this SDR and dsp thing, I am working on a project that calculates the ppm and adjusts the offset, now I kinda got the idea of how to calculate the ppm after going through the ...
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5 votes
1 answer
278 views

Failing to detect Hydrogen line with 105cm dish

I've seen many examples of roughly 1 metre sized dishes being used w H+ sawbird and an SDR to detect and analyze Hydrogen line signal, and have been trying myself but can't seem to get anything beyond ...
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0 votes
2 answers
69 views

Not able to understand some operations in rtlsdr library in python

Here is the part of the program I am having problems with: samples = sdr.read_samples(16*1024) power, _ = mlab.psd(samples, NFFT=1024, Fs=sdr.sample_rate /1e6) ...
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2 votes
1 answer
98 views

Why does QPSK signal in GNU Radio shift away from my center frequency at higher frequencies?

I am transmitting a QPSK signal via GRC and when I look at it on the spectrum analyzer, the signal is shifted away from my center frequency. This shift increases the higher the center frequency (i.e. ...
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0 votes
1 answer
458 views

Writing "Wav" file in GNU Radio 3.9.0

I need to burn an audio file received from a computer sound card. But in the new version of the gnu radio, I found that the "Wav File Sink" and "Wav File Source" blocks were gone. ...
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2 votes
1 answer
844 views

Implementing a BPSK and 4-FSK transmitters in GnuRadio (GRC) with USRP?

Currently trying to transmit a BPSK and a 4-FSK(MFSK) signal via GRC using USRP, I have two attempts at it but don't seem to be going anywhere. Still fairly new to GRC. For the BPSK, how will this ...
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7 votes
7 answers
784 views

How does IQ modulation work (intuitively)?

I'm trying to get my head around IQ modulation. What I understand so far is that each of the I and Q branches of the mixer produce two sidebands with the same frequency components, but in the Q branch,...
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3 votes
4 answers
1k views

How is the Hackrf able to achieve 20MHz of bandwidth with an ADC that only allows 22Msps?

The way I understand it, is that to avoid aliasing on an ADC, you have to be in the first Nyquist zone (so half the sampling speed). What doesn't make sense to me is how the Hackrf is able to bypass ...
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2 votes
3 answers
201 views

Constructing a ground level antenna array to monitor radio frequencies using SDR

New to this community and also a newish Ham. Hello everyone. This question could easily have been posted under 'Astronomy', but I thought I would start here since Hams tend to be quite knowledgeable ...
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6 votes
4 answers
745 views

Can SDR receivers be detected remotely?

It's my understanding that active superhet receivers can be detected by looking for the emissions from the local oscillator, particularly because the LO's frequency is usually set at some fixed offset ...
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2 votes
2 answers
138 views

Is it at all possible to make a ham alert radio?

Would it be possible to make an alert radio... for shortwave? Out of something like Arduino, or RPi. Sort of like the NOAA Weather Radios. I got to thinking one day. Say you wanted to send a message ...
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