Radio devices that use digital signal processing in place of analog electronic components to manipulate RF signals.
3
votes
1answer
34 views
FM spectral amplitudes during silence
General setting
I'm playing around with an RTL-SDR and recently captured some FM spectrum in Hannover, Germany. I want to undersand what's going on, so I've read a lot about FM and its spectra, but I ...
1
vote
0answers
86 views
LimeSDR Mini + Raspberry Pi 3 B+ Transmission problem
I am new at this. I would like to transmit an audio signal cleanly using WBFM but I see two signal peaks occur around my fundamental frequency when I start transmitting.
In this case I am using a ...
2
votes
0answers
33 views
SNR measurement for a BPSK/QPSK signal
I have created a software (gnuradio) that performs modulation/demodulation and supports a number of modulation schemes and error correcting codes. I'm in the process of evaluating the BER vs SNR for ...
-3
votes
1answer
54 views
where to look for (live or recorded) air traffic conversations for a specific area? [closed]
I am wondering if there's any chance to get a short fragment of ATC/pilot radio exchange of any flight to/from small airport of Talkeetna (Alaska). This airport seems to be not present on liveatc.net, ...
0
votes
2answers
118 views
HackRF + Amplifier = HF/VHF QRP Radio?
Do you think it would work to combine a HackRF One and an amp like the following to create a QRP SDR?
Link to eBay
Output of HackRF is approximately 10dBm, which fit's this amp nicely...
What is ...
5
votes
2answers
94 views
Advantages of IQ generation at Mixer Stage or within FPGA for SDRs
I draw two possible architectures for Software Defined Radios below.
In the first architecture, I,Q signals are generated at the mixer stage and two ADCs are required. The FPGA down-samples the ...
3
votes
1answer
152 views
GNU Radio sinusoid multiplication does not produce perfect results
I created a simple sketch in GNU Radio that multiples two signals. One is a sine and the other is cosine. I paste a screenshot of it and its results below.
I have heard that in DSP, we can do almost ...
1
vote
2answers
119 views
Fast TCP/IP radio modem on UHF band
I'm interested if it is possible to have a data radio modem that works on the UHF band 400MHz for TCP/IP communication.
What I have in mind is something similar to a router, but using UHF band for ...
2
votes
1answer
57 views
How high an SWR can the USRP 2901 (B210) handle?
I connected a USRP 2901 (B210) to an amplifier I designed. The USRP seems to shutdown every time I try to transmit. I guess I messed up with the input impedance matching on the amplifier. Is it the ...
4
votes
2answers
50 views
Weak signal digital modes and clock synchronization
Why to some weak signal digital modes (jt9, jt65, etc.) require knowing a clock time? Does knowing this clock time provide any gain in signal detection ability? (lower required S/N?)
What clock ...
3
votes
2answers
74 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.
...
3
votes
2answers
113 views
Sampling a 50MHz Max Frequency 50Mhz BW Signal with a 50MSPS 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 50MHz and 50MHz IF BW. In that case, is it possible to ...
5
votes
2answers
615 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 ...
3
votes
2answers
80 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 ...
5
votes
1answer
153 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
103 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
115 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
100 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 ...
1
vote
1answer
133 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?
2
votes
3answers
189 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
98 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
votes
2answers
41 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.
3
votes
2answers
66 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
101 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?
4
votes
2answers
280 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
141 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
77 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://...
4
votes
3answers
219 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
103 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
51 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
116 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
107 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.
...
8
votes
2answers
247 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
225 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
159 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
67 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
136 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
87 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 ...
5
votes
1answer
418 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 ...
4
votes
2answers
399 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
252 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 ...
2
votes
2answers
1k 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
683 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
296 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
323 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
118 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
457 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
744 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
246 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 ...
5
votes
2answers
308 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 ...
