Questions tagged [frequency]

Use this tag for questions about which frequencies to use or not use in certain locations/situations.

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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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1 vote
1 answer
293 views

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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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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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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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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4 answers
866 views

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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234 views

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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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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2 votes
1 answer
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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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2 votes
3 answers
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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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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 answers
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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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4 votes
2 answers
183 views

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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1 answer
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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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1 answer
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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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2 votes
1 answer
71 views

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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1 answer
194 views

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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1 answer
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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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3 answers
77 views

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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2 answers
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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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139 views

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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1 answer
118 views

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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1 vote
2 answers
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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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2 votes
3 answers
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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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3 votes
1 answer
314 views

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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3 votes
1 answer
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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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2 votes
3 answers
161 views

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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2 votes
1 answer
68 views

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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4 votes
3 answers
266 views

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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1 vote
0 answers
38 views

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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5 votes
5 answers
386 views

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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2 votes
2 answers
173 views

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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1 answer
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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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5 votes
1 answer
399 views

What is the best frequency to start working EME on a budget?

Well, the title says it all: I want to start making EME contacts with the lowest possible budget, and I doubt between 2m, 70cm and 23cm. Since I cannot afford those expensive power amplifiers for ...
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1 vote
2 answers
267 views

What frequencies in 118–173 MHz can I transmit on without a license in Canada?

I have a Kenwood TM-261. It has the frequencies from 118 to 173 MHz. What frequencies can I transmit on without a licence?
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175 views

Why are some frequencies "live" where is nothing

I was ham surfing on the 2 meter FM band on my C Crane 2E Radio and occasionally I come across these frequencys that are "live" but no Audio came through. The way I know that a frequency is dead is ...
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1 vote
2 answers
327 views

How to use FE-5650A rubidium frequency standard?

I bought a FE-5650A rubidium standard reference from eBay in the hope I can readily use it: https://www.ebay.com/itm/142361240786 Unfortunately this is far from "reasily useable". First and ...
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Why does the 60 meter band have special operating characteristics?

Why does this band have special operating characteristics and what do they mean.
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1 vote
3 answers
138 views

can I still hear a frequency if I can only tune in 5 kHz off?

I'm trying to listen in to the telemetry frequency for Wallops Island which is 411.325 MHz. When I punch this into my radio (Baofeng UV-5R), the closest I can get is 411.320 MHz. Will I still be ...
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1 answer
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What is "up" and "down", and is it consistent with "top band"?

If I understand things right if you go "down" to "lower bands" you eventually get to "top band", which is 160 meter band. Since this doesn't make any sense to me, is there something I'm missing? You ...
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1 vote
2 answers
927 views

GMRS not transmitting within a half mile

I recently got my GMRS license from the FCC, and I wanted to try out a couple radios for hiking and emergency communication. I have two tenway UV-5R pro radios (these do have an FCC ID) that are set ...
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4 votes
2 answers
506 views

What causes the light and dark bands (of background noise) in an HF waterfall display?

While monitoring the 40-meter band (among others) throughout a typical day/night as propagation changes I have noticed there are often bands of very low noise (black area) and others with much higher ...
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what is the center frequency

in GRC for this source block ?
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2 votes
2 answers
280 views

Full Duplex Radio Communication On a Single Frequency

I am an ELECTRONICS final year student and I am working on a project, "Full Duplex Radio On a Single Frequency". So is it possible to design such a project. If so then give me the idea about it, how ...
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