Questions tagged [frequency]
Use this tag for questions about which frequencies to use or not use in certain locations/situations.
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What's the deal with 7.200 MHz LSB?
I was scrolling around on my radio and came across an interesting conversation on 7.200 MHz. There were saying something about how Biden is using food stamps to launder money from China. I checked ...
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Questions about a Realistic Pro-25 Scanning Receiver
Almost complete noob here. I understand basic concepts of radio, frequency, the reason for clock crystals, etc, but not how it all works together in a circuit. I love to play with gadgets and that is ...
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FSK: Selecting center frequencies and Carson's Rule
I'm implementing 2FSK and 4FSK modulation schemes for an experimental system. I'm using GNURadio, although that shouldn't affect the question.
I'm trying to figure out how the center frequency should ...
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Exposure to AN/FRD
Why are Wullenweber CDAAs obsolete?
My dad worked inside the FRD sites on various Navy duty stations and is suffering now from Parkinson's and dementia. Has anyone else heard or read of similar side ...
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3
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Why can a monopole antenna receive wavelengths significantly longer than its physical length?
I am new to ham radio and have been playing with a RTL-SDR receiver to which I have connected a vertical 1.5m monopole antenna.
However, I can receive transmissions belonging to the 40m band (albeit ...
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How do the governments trace the frequencies such as satellites?
During Woman, Life, Liberty protests Elon Musk activated Starlink in Iran and yesterday reported that 100 devices are active right now.
Since it is illegal to have the device in Iran, how do the ...
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389
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How is FT8 modulated with both upper side band and FSK?
This Wiki shows FT8 mode is USB and its modulation is FSK.
I don't get the difference ...
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57
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Will two GPSDO units be precisely in phase with each other?
I always thought of a GPSDO as only a precise frequency reference. But the GPS and other GNSS systems also deal with rather precise UTC/TAI-ish time!
Are the outputs of any two GPSDO units generally ...
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What frequency ranges are most common for Amateur radio astronomy and why are most parabolic antennas tuned to such high frequencies?
What frequency ranges are most common for amateur radio astronomy?
I am mostly interested in radios for the purpose of astronomy. In general I was expecting that the lower frequencies would be more ...
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Why do radio operators sometimes use meters and other times use hertz?
I understand the conversion between meters and Hz, kHz, MHz, etc. but I don't understand why ham operators frequently switch between using one or the other.
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Commercial UHF bands in Sweden
I was investigating satellite (onboard) UHF transmitters. Some of them support commercial and amateur bands. To my understanding, amateur bands span between 430 to 440 MHz and commercial UHF between ...
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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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Why is there a repeater on 146.46? Isn't that a simplex frequency?
I have a commercial GE Phoenix transceiver that I sent out to be programmed on 146.460 but have been informed by a club that my transmissions are interfering with their repeater that has a 146.460 ...
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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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505
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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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answer
151
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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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answer
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Why is 9 kHz the lowest frequency for spectrum analyzers?
I researched a number of spectrum analyzers and it seems that the lowest frequency that these operate at is 9 kHz.
Why is the lowest frequency supported by spectrum analyzers 9 kHz?
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What if all ham/Amateur radio frequencies are occupied, as ham/Amateur radio operators are increasing
What if all ham/Amateur radio frequencies are occupied, as ham/Amateur radio operators are increasing.
If one ham radio operator wants to talk to other operator(s), at least one frequescy is needed ...
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How to transmit computer audio to a wireless microphone receiver? [closed]
I'm currently trying to broadcast my computer's audio output to a wireless microphone system receiver so that I can accompany my school's coming presentation with music. The frequency range is 480-598 ...
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Is SSB and FM voice considered TDD or FDD (and what are TDD/FDD)?
We are looking at the Qorvo QPL9547 LNA and the datasheet notes:
For TDD Applications: R1 = 0Ω & R2 = 100K
For FDD Applications: R2 = 100K ‘OR’ Pin 6 tied to ground. R1 = DNP/Omitted
This will ...
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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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610
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How to shift frequency with sine signal?
cosine signal can make square signal shift frequency.
If I have only sine signal source,how ...
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2
answers
487
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What cause the spectrum peak of `center frequency`?
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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How to record and replay the `center frequency` when `file_sink`?
Workflow as below:
When file_source after file_sink,center frequency is not recorded and ...
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answer
125
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How the ELF-VLF background noise spectrum looks like?
In the ELF-VLF frequency band,some background noise like Schumann resonances shows in the spectrum analyzer as peaks.
I want to have a overview look of the background noise of ELF-VLF frequency band,...
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3
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312
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Increase transmit and receive frequency of handheld transceiver
I'm new to the world of ham radio so this might be obvoius, but I have a Baofeng UV-82 which can transmit and receive up to 520MHz. I need to be able to transmit and receive on frequencies up to 1GHz. ...
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72
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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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4
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240
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What cause `multiply` has difference result between `float` and `complex` signal?
Construct 2 similar flow graph in Gnuradio,just different with data type.
complex type data has a correct result.But ...
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votes
2
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549
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Why does a sine wave show two peaks in the frequency domain on GNUradio?
I constructed the flow graph in GNUradio 3.7 as below:
I know a sine wave has only one frequency, so what causes the frequency sink to show two peaks?
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356
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Gnuradio bandwidth of sink cause signal frequency changed?
System is debian 10 with gnuradio 3.7.
untitled.grc create simple flow graph as below:
The only difference between 2 flows is bandwidth of gui sink,cause 2 ...
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Looking for a model or description of an EME channel
I am looking for any technical/scientifical/specialized reference describing in some detail the moonbounce for VHF/low UHF frequencies.
More precisely, I would be interested in a paper or publication ...
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Is it possible to set a precise frequency with a Btech 50x3 or am I stuck with being off frequency all the time?
I can't seem to figure out how to set it to the simplex frequency, 146.520. Always skips to 146.525 or 146.500.
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Receiving shortwave frequencies from different countries (e.g. North Korea)
This question may be a little strange, but how can I receive radio waves from a country like North Korea (when I live in Poland)? I am interested in this topic, but I don't have that much knowledge. ...
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203
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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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change LC parameter digitally
LC circuit is the main element of every frequency generator, I intend to make an FM transmitter, but many opensource circuit use analog variable L or C part to set and adjust the target frequency
My ...
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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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How do I set the RX frequency on a R820T/ R820T2 based SDR
My question relates to the specific programming of an R820T/ R820T2 based SDR for a specific frequency.
I'm trying to build a self contained and auto initializing Raspberry Pi 4-based (ignore that ...
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Frequency selective surfaces working principle
I've seen that sometimes frequency selective surfaces are used to load a certain impedance to a certain antenna (for instance for input matching purposes).
These surfaces act like a filter on the ...
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How many cars/devices can connect to a transmission from a 7 Watt FM transmitter
I currently own a 7 Watt Frequency Modulation (FM) transmitter that I purchased from eBay some years ago.
We are planning a drive-in cinema setup where the transmitter will be placed 5 meters above ...
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what is the baseband for CATV?
I was reading on wikipedia this:
the subscriber's television or a set-top box provided by the cable company translates the desired channel back to its original frequency (baseband)
But when I ...
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What do old unit abbreviations like "mfd" and "kc" mean, and where did they come from?
I saw a recent answer that mentioned "mfd" as a unit of capacitance, and I can recall having seen that term in old schematics and ham radio articles. I've also seen other non-SI unit ...
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Fourier transform of air breakdown impulse waveform
i am a beginner on signal processing.
I learned from some papers, site online, including this forum that lightning discharge or any electrical arc emits wideband radio frequency. because the odd ...
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Receiving multiple signal
Maybe this is a really silly question even from me, a completely amateur...
But I like to know about how's the antenna output when its receive multiple signal
Is it possible different signals on ...
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Signal frequency domain
Hello I am a beginner on radio and also In speaking english. I hope you will understand what I say.
Let's say I have an impulse generator and the air gap breakdown. I am already able to see the ...
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Electromagnetic signal from spark gap
I am a power electrical engineer college student, and I have a project to make an antenna for magnetic direction finding.
My main topic is to detect lightning strikes, but its to hard due to ...
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Labview Spectral Monitoring (USRP) - Bandwidth expansion and frequency change
I connected USRP (together with antenna) to my computer to receive some signals. For this purpose, I used the built-in module "Spectral Monitoring (Interactive)". Unfortunately I noticed ...
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How can a tuner pick up a specific frequency?
The point I'm confused about is the antenna. Depending on the environment, there are tons of different frequencies passing through you (FM, AM, 4G, SAT, etc). The electrons in the wire will move as ...
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Output power from the TX/RX port of the USRP N210 decreases as the frequency increases
I am trying to build an FMCW radar using a USRP N210 with a CBX40 daughterboard. I generate a sweep from 1.5GHz to 5GHz. According to their respective datasheets, the daughterboard and the USRP should ...
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363
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Upconvert Signal with USRP N210 in GNU Radio Companion
I'm using a USRP N210 with this GRC diagram where I'm trying to upconvert a 1kHz sinewave.
I tried just upconverting the signal from the signal source to 2.5GHz. However, I keep getting the output ...
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FMCW radar with USRP and GNU Radio Companion
I am new at gnuradio companion and USRP and I am a little bit confused with UHD:USRP Sink block. I am trying to build an FMCW radar in USRP N210 with CBX40 daughterboard. I want to generate a sweep ...
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