Questions tagged [frequency]
Use this tag for questions about which frequencies to use or not use in certain locations/situations.
94
questions
2
votes
1answer
85 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. ...
0
votes
1answer
40 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 ...
0
votes
3answers
74 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 ...
0
votes
2answers
46 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)
...
0
votes
2answers
78 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 ...
4
votes
1answer
100 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 ...
1
vote
2answers
144 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 ...
2
votes
3answers
82 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 ...
3
votes
1answer
153 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 ...
3
votes
1answer
40 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 ...
2
votes
3answers
112 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 ...
2
votes
1answer
65 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 ...
4
votes
3answers
218 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 ...
1
vote
0answers
33 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 ...
5
votes
5answers
166 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 ...
1
vote
1answer
81 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 ...
0
votes
1answer
66 views
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 ...
0
votes
1answer
165 views
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 ...
4
votes
1answer
139 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 ...
1
vote
2answers
181 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?
0
votes
1answer
171 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 ...
1
vote
2answers
189 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 ...
0
votes
1answer
129 views
Why does the 60 meter band have special operating characteristics?
Why does this band have special operating characteristics and what do they mean.
1
vote
3answers
117 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 ...
3
votes
1answer
111 views
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 ...
1
vote
2answers
769 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 ...
4
votes
2answers
324 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 ...
0
votes
1answer
94 views
2
votes
2answers
192 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 ...
0
votes
1answer
98 views
Locate a ball 1000 times a second
I want to locate a small ball in the air 1000 times a second. The ball is thrown from the ground and then flies in the air for 0.5 seconds until it lands. Distance from the location instrument is 1 ...
1
vote
0answers
107 views
communication with underground mines?
I have a meter that will analyze limited RF spectrum in my area. One frequency that keeps coming up is 2.498 kHz. An FCC site listed that as the frequency used to communicate with underground mines. ...
1
vote
0answers
62 views
Can my neighbors ham radio station be preventing my TV antenna from proper reception? [duplicate]
I have a winegard 8200 series antenna and it worked flawlessly in getting me reception of more than 70 stations. The wind blew it down and I couldn't replace it for about 6 months due to the fact that ...
3
votes
0answers
109 views
GnuRadio RF transmission, legal and safety issues
I'm trying to run some transmit/receive RF examples that I found online using GNU Radio with USRP B200. I read and heard about some cautions in terms of transmitted frequencies here in the USA which ...
5
votes
4answers
2k views
How does a receiver know the exact frequency in the channel to “listen to”?
I am reading about how radio communication works and I have an unanswered question.
We have wideband channels with 25kHz of radio spectrum. The transmitter modulates a signal and sends it.
The ...
3
votes
3answers
177 views
Applications for 100 GHz band?
I was reading this paper and I found it very interesting and the following question came up,
What are the main applications (what is used for) 100 GHz band?
I couldn't find any reference on what is ...
5
votes
2answers
82 views
Why do receiver sensitivities vary so much with frequency?
I was looking for a 2.4 GHz WiFi antenna to catch a weak free WiFi signal, and amplify it so I can use it. I found Ruckus Metroflex NG, which can receive signals down to -108 dBm. Which is amazingly ...
4
votes
3answers
232 views
What are these antennas used for?
I noticed this antenna park in Heidmoosstrasse, Switzerland. What is it used for?
4
votes
1answer
273 views
What are Radio-location Services in the 1.9-2.0 MHz range?
I'm currently studying for the General Exam and in looking at charts of the new frequency privileges have run across a restriction I would like to have further defined. In the 160 meter band the books ...
0
votes
1answer
60 views
Can radio waves be made to travel as or along a particle beam? [closed]
Can a laser be used as an antenna?
Can a beam of any type extend transmission distance of an electromagnetic field?
https://medium.com/starts-with-a-bang/this-is-why-the-2018-nobel-prize-in-...
5
votes
2answers
900 views
What is the frequency range 2300-21950 kHz used for?
I was checking out the gizmo mentioned in this question, and I see that it can receive "shortwave" in the frequency range 2300-21950 kHz. Most times I see "shortwave" mentioned, it's by sales or ...
5
votes
2answers
2k views
What is inside a 50 ohm termination?
I see RF applications requiring 50 ohm termination to avoid any open port reflections. Curious what is actually inside a 50 ohm termination connector. Is it simply a 50 ohm resistor? But then it is ...
5
votes
1answer
353 views
Can my laptop pick up CB radio frequencies?
I was on my laptop watching a show and I paused to look something up and since there was no sound I could hear a voice talking. It sounded distorted like it was coming over a radio and I couldn't make ...
7
votes
1answer
197 views
Why are radio frequency ranges aligned on multiples of 3?
Why are the radio bands organized by multiples of three?
For example the HF band is from 3–30MHz and UHF is from 300–3000MHz. Why not multiples of 2? Or plain powers of ten?
9
votes
2answers
376 views
Why do the ham radio bands get broader with increasing frequency?
The ham radio frequency allocations tend to comprise a larger frequency range for increasing frequency (also see this plot). For example, the 40 meters band is from 7,0 to 7,2 MHz, thus 200 kHz, while ...
2
votes
3answers
272 views
Radio Range vs. Frequency [closed]
Let's say you have two mobile simplex transceivers running on (for example) SSB. Mobile means that the antenna height and TX power have limitations. Say if we limit the Antenna height to 2m and the TX ...
8
votes
4answers
2k views
How to tune an FM transmitter to a specific frequency?
I am planning to organise a simple fox hunt, a family event. This includes building a transmitter. I am currently considering the following schematics:
https://maker.pro/education/diy-fm-transmitter
...
5
votes
1answer
413 views
What are these continuous sine wave tones I keep hearing?
I'm messing around on WebSDR and by just scanning through I sometimes come across these continuous tones in USB. One in particular was 28.800 MHz USB.
I've picked them up on nearly every WebSDR unit ...
0
votes
1answer
91 views
Are there receivers and transmitters that can be tuned to multiple frequencies at once? [closed]
What kind of hardware/circuitry would be needed for a device to be able to transmit and receive over a range of frequencies at once?
2
votes
2answers
88 views
Antenna Q vs pattern shape
Is there any reason to think that changing the Q of an antenna would affect the directional pattern, assuming that is the only variable that changes?
Restricting to values of Q say less than 1000.
...
3
votes
3answers
848 views
Can 2 uhf beam yagi antennas be used on a transmitter to get a diversity effect?
I'm having a problem getting a good signal up to a repeater site on UHF. I'm running 20W in a neighborhood with lots of trees, and the signal is fading in and out due to trees and the wind.
I can't ...
