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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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4
votes
2answers
108 views

Can a Digital Down Converter, at the same time, generate I,Q streams & Downconvert?

A Digital Down Converter (DDC) is usually used to convert Real Digital Signals at a high frequency to baseband (centered around 0Hz). DDC does this so by producing negative and positive frequencies. ...
4
votes
2answers
297 views

Sampling a 50 MHz Max Frequency 50 MHz BW Signal with a 50 MSps ADC

I paste below a superhetorodyne based Software Defined Radio Architecture for an Rx channel below. Suppose the IF signal has a max frequency of 50 MHz and 50 MHz IF BW. In that case, is it possible ...
8
votes
2answers
704 views

IQ imbalance after quadrature mixing

What is IQ imbalance in the output of complex or quadrature downconverter/demodulator/mixer? What are the causes and effects of IQ imbalance? (A spike in the spectrum display of RF noise?) Are there ...
4
votes
2answers
188 views

SSB filtering in the frequency domain?

I'm not sure whether it's more appropriate to ask this question here, or in the dsp.stackexchange. But I'll try here first. There seems to be a lot of information available on the filtering and ...
6
votes
1answer
342 views

What is “Billion Code” for garage door openers from around 1996?

I've been trying to "hack" my garage door using an SDR (LimeSDR) for a high school physics project, and I have run into a snag. When I look at the signal and demodulate it using ASK in Ultimate Radio ...
5
votes
2answers
212 views

Doppler shift compensation without using predictive modelling

Doppler shift mitigation has been studied extensively in the literature. In my implementations of satellite receivers (using GNU Radio), I use predicted Doppler shift from a software (GPredict) to ...
1
vote
2answers
137 views

What wireless communication technologies can travel long distances with a high bandwidth?

I couldn’t find a better place to ask this question, so I have asked it here. I am looking to transmit and receive internet connectivity wirelessly over a distance of 6 miles (9.7 km) with a minimum ...
3
votes
1answer
394 views

What are the maximum possible speeds of download over Amateur Radio frequencies?

In this scenario, I would have a base station connected to a modem that essentially allows me to access the internet/local network via radio, irately I am not fully aware of what information I need to ...
2
votes
1answer
230 views

Is MFJ-1708SDR safe with RF switching

I just got an SDRPlay and an MFJ-1708SDR transmit switch. I use the the PTT on my Flex to key the amp, so I am wondering if the RF sense is fast enough to protect my SDR radio?
3
votes
3answers
349 views

Is there an FT8 or other weak-signal digital mode specification available?

Is there a complete and programming language independent specification available for the FT8 digital mode? Detailed enough to implement both transmit and receive SDR software from scratch in two ...
0
votes
1answer
133 views

Playback entire FM Band

Is SDR technology a way for me to listen to a large group of stations or even the entire FM band at once?
0
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2answers
57 views

SDR (RTL-SDR v3) USB audio much less than LSB

Why does USB have so much less audio output than LSB? I've checked all settings and they are correctly set or not used, like AGC etc. Using same band pass on both modes.
2
votes
2answers
99 views

FFT showing evenly spaced signals when tuned to ~56 MHz down to 25.680

I'm running GQRX on Mac OS X 10.11.6 hooked up to an RTL-SDR dongle. I noticed when I'm tuned anywhere between ~56 MHz on down to 25.680 MHz I see evenly spaced signals on the FFT. But when I tune ...
2
votes
2answers
127 views

Measuring dBs with software defined radio

If the "floor" of the graph in my SDR is at -110dB, and when I key up, it goes to -70dB, and the wattage is 5W....is there a direct correlation between dBs and wattage?
3
votes
2answers
456 views

Understanding WFM modulation

I am using "HDSDR" software to demodulate a WFM broadcast ("Classic FM" in the UK, on 100.1 MHz, 192 KHz bandwidth). I'm using an "SDRPlay RSP1" software defined radio and a cheap indoor discone ...
1
vote
1answer
507 views

SDR - discone antenna setup

Here's a picture of my SDR receiver setup... This entire setup lives indoors as I'm not able to put anything up on the roof right now. My understanding of a discone antenna is that the downward ...
0
votes
1answer
96 views

Tx-Rx synchronisation to frequency changes

So I am part of an SDR project using GNU Radio and USRPs, where we are trying to set up a link between USRPs. The ideal is similar to the DARPA spectrum challenge (https://...
5
votes
3answers
458 views

SDR set up that will TX & RX on CB, UHF and VHF

I would like to use SDR to receive and transmit on CB, UHF and VHF. Is this possible and if so what type of equipment will I need (antennae, dongle etc)? I currently have both UHF/VHF and CB but atm ...
2
votes
1answer
116 views

How to find transmitting (voice and CW) Amateur stations in UK?

Background info: I own an SDR (model "SDRPlay RSP1") and I have a fully working HDSDR software system installed on my PC. I can successfully use this to tune-in to my local airport's radio traffic ...
0
votes
1answer
56 views

Buffering Delay/ Jitter between voice calls

I have designed a TDMA protocol to reduce the voice spurts between voice calls in SDRs. The protocol runs in this manner: control cycles proceeded with data cycles and again control cycles. Control ...
3
votes
1answer
211 views

How can I determine if out of band interference is affecting my AIS reception?

AIS I am receiving ship AIS messages. These are low power, digital messages periodically sent on two marine channels close to 162mhz. This frequency is surrounded by FM broadcast, weather radio, and ...
1
vote
0answers
203 views

Is there any open-source solution to scanning / decoding GSM/UMTS traffic? [closed]

I want to build a passive (rx-only) scanner to listen to GSM and UMTS traffic. I am not interested in breaking encryption or anything like that - but more interested in collecting statistics and such. ...
10
votes
2answers
600 views

Multiple simultaneous tunings with SDR

I just found out about WebSDR, and I was wondering how is it possible that many listeners listen and tune to different stations simultaneously. Which components/technologies allow this, and how does ...
0
votes
2answers
386 views

Hopping from one frequency band to another in SDR (ex: USRP)

This question is not about Frequency Hopping Spread Spectrum! In SDRs, say USRP, if we are transmitting in a particular frequency band, can we dynamically hop from that band and transmit from ...
1
vote
3answers
281 views

Viewing the broadcast FM spectrum using a USRP N210

My issue is regards to viewing the FM spectrum using USRP N210 & GNU Radio. I did try to use several blocks of GNU Radio to view an FFT plot of the FM band using the USRP N210 device. My blocks ...
3
votes
2answers
94 views

GNU Radio - Signal Keeps Getting Smaller?

Really bizarre issue here. Here is an image of a signal taken from SDR Sharp: Freq: 926.365M Bandwidth: 30k Now, using the above measurements, here is this same signal observed in GNU Radio with ...
1
vote
1answer
427 views

I want to know the bandwidth of this signal; problems using “QT GUI Frequency sink” to show it

As shown in two pictures,setting a different bandwidth-value in the module, the value of the coordinate axis change accordingly. How did it happen? And I want to know if gnuradio can tell us the ...
2
votes
0answers
308 views

Does anyone repair Flex radios other than Flex Radio?

A local ham that I have an evening sked with on 75m (Paul, W0EBV) sent his Flex 5000 SDR transceiver to Flex Radio Systems to get it repaired a few months ago. However, it seems that Flex is either ...
6
votes
1answer
972 views

RX antenna and RTL SDR with upconverter ..How to hear something?

I mounted a small RX antenna (mini whip, bought from eBay) (on 10-th floor) and I want to try to listen to something. I bought a RTL-SDR with Upconverter which supports HF. RX antenna's operating ...
5
votes
2answers
844 views

How to transmit images and video through a hurricane?

Background You're in the path of a hurricane, and the eye just passed over your head. There is no electricity (apart from your own generator or battery), there is no mobile network and there is ...
2
votes
1answer
470 views

USRP: Are RX and TX on the same or different channel for single daughterboard?

I've got a USRP X310, currently with just one daughterboard, a WBX-120. I'm writing some C which needs to operate the radio full duplex - I receive on RF A RX2 and transmit on RF A TX/RX. But I'm ...
3
votes
2answers
2k views

Choosing a wideband antenna design

On a previous question I asked about proper antenna design for wideband SDR receiver and ways to improve signal/noise ratio. Ideally the reciever has a range of 100kHz-2GHz. Keeping in mind is ...
3
votes
3answers
1k views

Broadband antenna for SDR radio

I recently bought a very wideband SDR receiver (DX-Patrol MK4, declared covered frequencies are 100kHz-2GHz). I'm experimenting with antenna designs because unfortunately I live in an apartment ...
1
vote
1answer
689 views

Why is GNU Radio dropping packets when I introduce a Frequency Xlating FIR filter?

I've got a GNU Radio flowgraph intended to take a signal from a USRP X310 at a 25MS/s sample rate and downsample it to 2.4576MS/s for demodulation as 9600 baud GMSK. If I run the USRP straight into a ...
2
votes
1answer
436 views

Serialising a data signal with a Raspberry Pi

I'm working on a project to transmit and receive data by radio. For the transmission, I'm using a Raspberry Pi 3 and the NTX2B transmitter for the transmission. For the receiving end, I am using ...
0
votes
2answers
130 views

Any ideas as to what I might be picking up on SDR?

Any ideas as to what I might be picking up on SDR? They make for some strange patterns. Picked them up at the following coordinates: (31.514596, 74.345092) using GQRX, tuned to 217.25 MHz. As for the ...
1
vote
1answer
942 views

How to change center frequency automatically in GRC?

I'm on reasearch using USRP and GNU radio for solar flare observation. The research is making digital radio receiver in GNU radio companion and using USRP B200. Basically the purpose of system is to ...
1
vote
1answer
2k views

How to make GRC flowgraph run and stop automatically during some period

I have beacon receiver program the flowgraph is shown here I have to make the flowgraph run and stop automatically during a preset period, because I have to make the flowgraph only work when the ...
1
vote
1answer
352 views

How to make a software defined radio using USRP and GRC

I want to make a software defined radio, based on the hardware device shown in the schematic diagram below. I don't have a strong background in telecommunication engineering (I'm an electrical ...
6
votes
2answers
464 views

Filtering for PSK31 demodulation

What's the ideal filter for PSK31 demodulation? That is, something that minimizes ISI, while having a narrow bandwidth to reject adjacent channels, while being reasonably matched? Most PSK modes use ...
4
votes
2answers
353 views

SDRPlay RSP1 and broadcast band (AM) interference

I heard the SDRPlay RSP2 has an AM notch filter, but I don't want to spend that much money. How is the RSP1 for broadcast band interference? Will I need a preselector? I already have an MFJ-1020c ...
2
votes
3answers
339 views

What are the 3 or 5 peaks in an FM broadcast during silence?

Looking at the waterfall spectrum of any ordinary FM public broadcast station (88-108 MHz), during the silence, there are 3 or 5 visible peaks. What are they? It's possible this has a trivial ...
3
votes
1answer
356 views

What is this Morse code-like station?

I’m trying to identify this signal at 928.807 MHz. A sample of the raw I/Q from gqrx is here (9.2 MB, .wav, 48000 Hz) and this is the waterfall: I’ve tried decoding some common digital modes (...
5
votes
3answers
1k views

Cause of harmonic spurs?

Harmonic spurs (harmonics of the transmitter frequency, as seen by a wide-band receiver or SDR) in the RF spectrum might be caused by an imperfectly sinusoidal or badly filtered transmitter carrier ...
2
votes
2answers
132 views

How to safely connect a digital output to a receiver's antenna input?

Suppose I have a 3.3 or 5V GPIO digital signal (from an Arduino or Raspberry Pi, etc.), periodically toggling at some HF or VHF frequency. Since it has such a "dirty" spectrum, I don't want to hook ...
1
vote
2answers
1k views

How to best connect an FM transmitting GPIO pin to an antenna?

I'm trying to use a RaspberryPi3 as a FM transmitter, using pifm and/or PiFmRds to send audio in 88-108 MHz band. The RPi can then use the GPIO-4 pin to transmit between ...
4
votes
2answers
2k views

Where can I find a listening guide for different frequencies and their usages to listen to on SDR?

I just got an RTL-SDR dongle by Nooelec and am using CubicSDR on Mac (which supports AM, FM, and SSB), and I'm in Canada. I'm able to easily find FM radio stations, but outside of that I'm not sure ...
5
votes
2answers
2k views

How to determine the PPM value of a NESDR SMArt?

a) Given that I don't have a frequency standard or other known transmitter available, what is the easiest way to calibrate the NooElec NESDR SMArt which is using a TCXO rated at 0.5 PPM.? I.e. to ...
3
votes
2answers
1k views

Where can I download NESDR Smart (NooElec) drivers for Mac OS Sierra?

Just bought this NESDR Smart USB dongle from Amazon in Canada. Wrote the company asking for drivers, but they sent links which didn't help. Anybody have a better place to download drivers for Mac OS ...
2
votes
2answers
68 views

What function do high-pass filters in a direct conversion receiver perform?

Use case: I'm considering hacking into my SoftRock RXTX to bypass the filters, then add external filters. I'm wondering if I can use just the low-pass filters I've already built, or if there's a ...