Questions tagged [dsp]

Questions about digital signal processing, whether of RF, audio, or digital signals. For RF, consider [software-defined-radio].

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3
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2answers
185 views

Why does beamforming bring more power to the received desired signal?

Consider a normal array model with $N$ element. The output of the array is given by, $$\mathbf{y}=\mathbf{w}^H\mathbf{x}=\mathbf{w}^H\mathbf{as}$$ where $\mathbf{a}=[a_1,...,a_N]^T=\in\mathbb{C}^{N\...
2
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3answers
740 views

What exactly is the IF output on radios?

My Kenwood TH-D74 and ICom 7300 both have the ability to output IF instead AF. Is this IQ signal at 12ksps, meaning 12kHz of bandwidth, or something else? What are some projects that can be done with ...
4
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2answers
347 views

Problem with sample rate

So I am working on a project that involves me to check real time difference between samples.I am fairly new to this so after a bit of researching I wrote a simple python script for it, here is the ...
0
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1answer
54 views

GNU Radio transmission for a set amount of time

I am trying to transmit a signal in gnu radio and after a set amount of time have the transmission cut off. For simple example, I have a sine wave that I want to transmit for 30 seconds then after ...
2
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1answer
78 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. ...
2
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1answer
437 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 ...
3
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1answer
85 views

Modeling a regenerative receiver

What is the signal processing model of a simple regenerative or super-regenerative receiver? Is it just a linear 2-pole IIR filter with gain? How does a single regen control knob control both ...
2
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1answer
75 views

Transmit filter for Amplitude-shift keying

I want to transmit an ASK signal with GNU Radio and HackRF, the parameters are: Frequency: 27.12 MHz (ISM) Sample rate: 2MSPS Symbol rate: 2000 bps Samples per symbol: 1000 The flowgraph currently ...
4
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4answers
137 views

Understanding how quadrature heterodyning captures information from negative frequencies

The way I understand how SDR works, there is a receiver input, generally connected to an antenna pulling in signals from the ether. That input is connected to two mixers (linear multipliers), being ...
0
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2answers
51 views

Detecting receiver intermodulation distortion?

On some (most?) receivers, if the RF gain is turned up too high, intermodulation distortion increases due to increasing non-linearities (maybe even clipping, etc.) Is it possible, just by examining ...
2
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2answers
536 views

What is the current state of the art in CW filters?

In the 1970s I made a CW “filter” based on a phase locked loop that detected a specific audio frequency, and this drove an NE555 oscillator: the result seemed at first like a “zero bandwidth” CW ...
6
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4answers
528 views

How can quadrature mixing adjust the phase of all frequencies by the same amount? Can it be done in the digital domain?

This came up in some feedback I got when I tried to answer What is IQ in the context of SDRs? and revealed some of my own misunderstanding. Initially, I gave an answer something like (paraphrasing): ...
1
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1answer
964 views

How to send DMR SMS using MMDVM modem or hackrf?

I have a baofeng DMR radio with SMS feature, and since there is not much DMR radio owners in my area I want to do something myself. The easiest thing I can do I thought is to send myself some SMS as ...
2
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0answers
85 views

Which digital modes are formally specified sufficiently to be implemented?

Which currently popular digital/SDR modes do not require a pre-compiled library or pre-written source code? (e.g. has actually been used for QSOs as implemented from specification or sufficiently ...
9
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1answer
547 views

Calculating the signal-to-noise ratio for CW (Morse Code) signals?

How is the signal-to-noise ratio for received CW and QRSS CW (and/or other ultra narrow-band DSP digital modes) typically computed? e.g. What noise bandwidth should be used to measure the spectrum ...
0
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1answer
53 views

Shifting frequency outside of the band

In theory when i need to shift some frequency i just multiply that signal by some sin or cos wave with the right frequency and than apply LPF or HPF. But when there is a wideband complex signal with ...
3
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1answer
100 views

Turning raw APT data into an image

I apologize if this question is a little out of scope for the amateur radio stack exchange but I feel like it fit better here than over in any other forum. I have successfully parsed raw PCM data out ...
6
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2answers
82 views

Can an ultra-wideband system transfer data at high speed without precise clock synchronization?

Recently, ultra-wideband technology has been in the news again. From the Wikipedia article: UWB transmissions transmit information by generating radio energy at specific time intervals and ...
3
votes
1answer
543 views

What is Spectral Subtraction for noise reduction?

I previously asked a general question about noise reduction, but none of the answers mentioned this specific method or algorithm. (the noise reduction button on some radios and DSP software seems to ...
5
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1answer
147 views

What does a receiver's noise reduction function do?

Some receivers contain a noise reduction button or function. What does this noise reduction do? Is there more than one type of noise reduction? How does the circuit or software know what part of ...
4
votes
1answer
67 views

Relative computational requirement for various digital modes?

What might be the relative computational performance requirements for the various popular digital modes? (FT, JT, WS, PSK31, etc.) I seem to recall FSK modulation/demodulation being done with 1 or so ...
2
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1answer
132 views

How narrow-band can a DVB-S2 signal be?

Using software defined radios I can generate and demodulate a DVB-S2 signal live. I'm wondering if I can use this to send single pictures over the air using as narrow BW as possible. Using QPSK and a ...
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2answers
393 views

Using Satnogs' *.ogg files in GNU Radio flowgraphs

I want to use the *.ogg files available in Satnogs' database to test demodulation software for several satellites (using gnuradio). Can I use the ogg file source (available in gr-satnogs module) and ...
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2answers
72 views

Is the Nyquist rate independent of the power of the analog signal being digitized?

In analog-to-digital conversion, how independent is the Nyquist rate from the power of the signal?
0
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1answer
69 views

Will the quantization noise be increased if the step level is increased?

Will the quantization noise be increased if the step level is increased? I was wondering about the relationship between the step size of the quantizer and quantization noise,
1
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1answer
276 views

AX25 + Reed Solomon : Bit stuffing errors

I'm currently working with a satellite that has AX.25 + Reed Solomon code (truncated RS(255,223)) in GNU Radio. Since there is no frame synchronization pattern, the 0x7e flags are used for frame ...
5
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3answers
275 views

Detecting signals using statistics

I have sampled a section of spectrum every few Hz. I have mean, standard deviation, and range data for every frequency sampled (and I can gather more statistics if necessary). I've sampled for ...