Questions tagged [radio]
The radio tag has no usage guidance.
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0answers
32 views
Help in identifying low speed image transmission protocol over RF
In the seventies I worked for Muirhead on press fax machines that used to transmit pictures over radio and landline as I recall two FM systems were used a carrier 800 Hz modulated +- 150 Hz and 1900Hz ...
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0answers
30 views
Why do IQ Impairements, Quadrature Skew and DC offset have these geometric effects on the constellation?
I'm studying telecommunications, and would like to be sure to understand the maths behind these effects.
For IQ Imbalance and DC offset, it seems pretty clear why we observe a rectangle shape or a ...
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1answer
80 views
Can a software defined radio with a frequency range of 300 MHz – 3.8 GHz detect AM (535 to 1705 KHz) and FM signals (88 to 108 MHz)?
I am interested in knowing whether BladeRF SDR with a frequency range of (300 MHz - 3.8 GHz) detect AM and FM frequencies? Also, how important is the sampling rate of the SDR. For example, BladeRF has ...
3
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0answers
55 views
Phase response of S11/S22 parameter for an RF attenuator? [closed]
I am new into the RF measurements. I was measuring the S11/S22 (reflection) parameters of an RF attenuator (with different attenuation levels, e.g., 10 dB) via a vector network analyzer from Rhode &...
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1answer
291 views
Trouble with time-syncing two radio signals using cross-correlation
I posted a similar question a while ago here (I'm posting this follow-up since I'd like to focus more on cross-correlation now). I have a setup where I have two software-defined radios connected to ...
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1answer
57 views
why transmitting a long pulse its spectrum gets spread?
I'm transmitting an RF signal with a CC1101 at 440 MHz.
This signal is a constant of 1, so the spectrum should be a delta.
Using a SDR dongle, I've checked the spectrum and it's wider than a delta ...
2
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2answers
276 views
How can I align these two signals? Cross correlation isn't working properly
I have two radios sampling simultaneously, and I am trying to time-align their two signals (they will always start sampling at slightly different times with random delays due to hardware differences). ...
0
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1answer
539 views
Checking for VHF pulse with SDR and python
So I have a small NooElec Software Defined Radio and I've got it working well with my Raspberry Pi using GQRX as a controller and to visualize the SDR output.
My goal though is to use a python script ...
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2answers
66 views
how to eliminate interference in the same center frequency
I'm trying to receive an ASK signal in the 433 MHz center frequency with a bandwidth of 100KHz. I'm using a CC1101 transceiver connected to a Raspberry Pi GPIO ports. However, there is an intermittent ...
0
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1answer
56 views
how to guess what the interference source it could be
At work, we are in an industrial area, and there is always a signal that I receive inside my office which interferences with my tests.
This signal is in the 433 MHz and when I see the spectrum, ...
0
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1answer
127 views
Why is Error Vector Magnitude (EVM) measured as an RMS value?
I do understand Voltage/Current measurement of a Sine Wave is in RMS, as average yields a zero, and RMS gives a true 'DC equivalent' value. But I do not understand why an EVM measurement could be in ...
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2answers
66 views
What is the relation between the carrier frequency and the attenuation of electromagnetic waves?
For electromagnetic waves, what is the relation between the the carrier frequency, attenuation (absorption loss) and propagation distance?
I know that modulating high frequency carriers are required ...
-1
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1answer
30 views
Output eqaution of a repeater?
Assume we have a signal repeater, a simple repeater that amplifies the signal then transmits it as is.
Does the output power of the repeater is dependent on the received signal at the repeater ?
for ...
3
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4answers
509 views
How can the I and Q components of a quatrature signal be different from each other (apart from the 90º phase shift)
I've spent many hours reading and doing research about this. I don't attend any university classes or any type of classes that may approach such a topic. I am trying to learn this by my own without ...
4
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1answer
679 views
How do I convert a real baseband signal to a complex baseband signal?
I have radio telescope observations that have resulted in two real-valued signals (corresponding to the right- and left-handed circular polarizations).
The signals are sampled at rate $2B$, and ...
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0answers
121 views
What kind of signal modulation is more resistant to jamming?
I've understood that spread-spectrum type of modulations are more resistant to narrow band jamming, for obvious reasons. What is less obvious is why someone would try to jam for example a cellular ...
1
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1answer
120 views
How to accurately model wideband RF reflections?
I would like to model a transmitter and received pair, both sampling at the same bandwidth (not clock synchronized), where there are a number of reflectors. The time delay due to the reflectors can be ...
3
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1answer
177 views
Recommendation for good ressources on digital processing and D-QPSK
I've been a C++ developer for 10 years. Quite high level. And I am completely new to Digital Signal Processing.
I am trying to implement a Software Defined Radio. Specifically I am trying to receive ...
2
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1answer
850 views
Measuring signal phase difference between receivers
I am working on a project which aims to locate a transmitter.
I consider doing this using several receivers and measuring the phase differnces between them.
My problem is that arduino measures once ...
3
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3answers
147 views
Real world application of signal sparsity?
There are theories based on signal sparsity in frequency domain like Compressive Sensing, Sparse FFT, etc. Throughout searching and studying papers I found out Cognitive Radio is a good example of ...
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1answer
84 views
Receiving multiple signals at the same frequency at the same time
I'm doing a project for my school it's a communication platform for different mobile devices I'm gonna build and I need to send data from the devices to station am making, I figured how to use signal ...
1
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0answers
45 views
Considerations when determining squelch
I asked this question recently. From the comments I learned that squelch is not a hard and fast thing, and that many considerations might go into determining a reasonable value, depending on use, the ...
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0answers
68 views
Coming up with a squelch value
I am building a scanning-type system. I have samples in $\textrm{dB}$ and I want to determine when to allow them through. I am trying to decide between allowing them through when they reach a ...
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2answers
221 views
If you had supersonic hearing, would you be able to hear the carrier wave of an AM radio station?
Would you be able to hear the carrier wave of an amplitude modulated station, if you could hear in the MHz range, or would the high frequency be filtered out after rectification?
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1answer
1k views
Possible to Derive Receive Signal Power from RSSI?
My Set-Up
I am sending packets at a specific frequency and with a specific gain from one N-210 USRP to another of the same model.
NOTE: I have the transmitting USRP connected to a series of ...
2
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0answers
252 views
Is GNU Radio a good choice still? [closed]
I'm a newbie at DSP. I am starting a hobbyist project where I plan to monitor 100's of wildlife radio collar frequencies (at my job) and record how many "beeps" per minute are received. My software ...
1
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1answer
103 views
Fully random PN sequence
Can a CDMA PN sequence be fully random, as in encryption-grade randomness, or must it be deterministic? I have tried the first bytes of SHA-256 hashes as PN sequences, but somehow they don't coexist ...
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0answers
32 views
Car engine audible through AM radio — what is this called?
A car's engine rotates in the range of 500 RPM to 6000 RPM. This is in the audible range. The car's engine is activated using spark plugs which are an electrical system at the same frequency (or some ...
4
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2answers
1k views
fmcw radar sampling requirements
I have been reading about "all-digital" or "software-defined radars". Lately, I was trying to simulate an FMCW short range radar in Matlab. One thing that struck me during the simulation is that to ...
1
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2answers
122 views
What are the fundamental reasons that suggest us to minimise transmission power for energy-efficient radio link design?
My question in short:
Under which scenarios minimising transmission power is beneficial in terms of transmitter energy-efficiency? is there any fundamental reason to keep a low-power oriented design ...
3
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2answers
272 views
Quadrature modulation
I have a question:
What is the difference between
$ I \cos(t) - Q \sin(t) $ and $ I \cos(t) + Q \sin(t) $
except that they are phase shifted 90 degrees ?
On the internet I can find both ...
0
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1answer
62 views
Modeling a signal through the environment
I have a signal that is composed of a sinusoid. I will send it over the air through radios. Part of the signal will go through processing on a computer, which means that it will be converted from ...
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3answers
598 views
Filtering out unwanted square wave (Radio: DCS/DPL signal)
I've need to remove a DPL/DCS signal from a recording. Roughly speaking, a DCS signal is a low frequency (67.15Hz) square wave sent at the same time, over the same carrier, as speech. Because it is a ...
