Questions tagged [frequency]

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

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Ham radio and repeater usage

I'm a newbie with radios and frequencies, but I was doing some tests to listen and transmit on one repeater near me (Cambridge MA) and it worked very well (as far as I understand). The problem ...
Mirjan's user avatar
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How does a band frequency is generated?

A band frequency is a range that start from a X frequency(lower one) to a Y frequency(higher one) but exactly and precisely how this is done i dont know how.i assume that the generator use a loop step ...
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What frequencies can a GNSS (Global Navigation Satellite System) antenna pick up?

Am sure that a GNSS antenna can pick up other frequencies than GNSS ones, so is there anyone who tested that theory?
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1 answer
160 views

When should I switch antenna inputs on the Yaesu FT-897D?

The Yaesu FT-897D has two antenna ports: "HF/50 MHz" and "144/430 MHz". The manual states: The "HF/50 MHz ANT" jack is used for HF and 50 MHz, while the "144/430 ...
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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 ...
owabs's user avatar
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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 ...
jewettg's user avatar
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187 views

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 ...
Jordan's user avatar
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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 ...
Monique's user avatar
3 votes
3 answers
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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 ...
Fabián Iglesias's user avatar
-2 votes
1 answer
99 views

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 ...
ElectronSurf's user avatar
6 votes
2 answers
550 views

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 ...
Dan's user avatar
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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 ...
natevw - AF7TB's user avatar
4 votes
2 answers
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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 ...
Hack-R's user avatar
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2 answers
399 views

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 ...
Moses Browne Mwakyanjala's user avatar
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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 ...
Koen's user avatar
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2 answers
792 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 ...
Dax's user avatar
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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 ...
kittygirl's user avatar
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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 ...
kittygirl's user avatar
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1 answer
190 views

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 ...
kittygirl's user avatar
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8 votes
1 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?
kittygirl's user avatar
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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 ...
ANUPAM's user avatar
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3 answers
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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 ...
user21397's user avatar
1 vote
1 answer
140 views

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
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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 ...
Jack Amoratis's user avatar
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0 answers
720 views

How to shift frequency with sine signal?

cosine signal can make square signal shift frequency. If I have only sine signal source,how ...
kittygirl's user avatar
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6 votes
3 answers
668 views

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: ...
kittygirl's user avatar
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-3 votes
1 answer
415 views

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 ...
kittygirl's user avatar
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2 votes
1 answer
189 views

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,...
kittygirl's user avatar
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2 votes
3 answers
428 views

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. ...
luek baja's user avatar
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1 answer
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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(...
kittygirl's user avatar
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0 votes
4 answers
311 views

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 ...
kittygirl's user avatar
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4 votes
2 answers
779 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?
kittygirl's user avatar
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4 votes
1 answer
439 views

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 ...
kittygirl's user avatar
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5 votes
1 answer
62 views

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 ...
user3141592's user avatar
2 votes
1 answer
77 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.
NonYaBidnezz's user avatar
2 votes
1 answer
351 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. ...
MagicMan's user avatar
0 votes
1 answer
251 views

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 ...
RasenRhino's user avatar
0 votes
3 answers
81 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 ...
Mehrdad Hrsk's user avatar
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2 answers
77 views

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) ...
RasenRhino's user avatar
0 votes
2 answers
308 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 ...
BigNutz's user avatar
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4 votes
1 answer
238 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 ...
Kinka-Byo's user avatar
  • 279
1 vote
2 answers
292 views

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 ...
Manny265's user avatar
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2 votes
3 answers
111 views

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 ...
sumer fattoum's user avatar
3 votes
1 answer
803 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 ...
rclocher3's user avatar
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3 votes
1 answer
97 views

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 ...
Ramanda Nvl's user avatar
2 votes
3 answers
469 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 ...
Ramanda Nvl's user avatar
2 votes
1 answer
73 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 ...
Ramanda Nvl's user avatar
4 votes
3 answers
358 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 ...
Ramanda Nvl's user avatar
1 vote
0 answers
47 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 ...
MagicMan's user avatar