Questions tagged [frequency]

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

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How do I report an emergency using ham radio?

If I'm in the wilderness with ham equipment but no phone signal, how would I report an emergency? Is there a particular frequency I would use, a particular protocol or suchlike?
berry120's user avatar
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12 votes
5 answers
51k views

What is the difference between channel & frequency & band in RF?

I am reading about wireless networks basics. I found three terms I cannot find exact definition for: channel, frequency band, frequency. Can anyone give exact definitions for them?
ashok's user avatar
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12 votes
2 answers
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What does a SSB frequency actually indicate?

An SSB signal is an AM signal with the carrier and other sideband filtered out, if I understand correctly. As such, when specifying an SSB frequency do you specify the carrier frequency, then state ...
Adam Davis's user avatar
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11 votes
2 answers
2k views

Why do some DX listen on a different frequency than they transmit on?

I've heard some DX indicate "CQ up 5" for instance, indicating that they are listening on a different frequency than they are transmitting on. What are the reasons one might want to do that?
Adam Davis's user avatar
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10 votes
2 answers
13k views

What is a "calling frequency"?

Doing some study for the ham test, I read a question asking about a certain “national calling frequency”. What is a “calling frequency”? What is meant by “calling” in this instance?
SunSparc's user avatar
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9 votes
5 answers
1k views

Why do Hams refer to bands by wavelength and not frequency?

I've noticed while reading literature and websites geared towards and written by amateurs and ham radio enthiuasts that frequency bands are commonly referred to by wavelength. In professional ...
YetAnotherRandomUser's user avatar
9 votes
4 answers
32k views

How can you calculate the frequencies for each band?

I've just started studying for my HAM license a couple of weeks ago, so please excuse me if this is a remedial question... I have the Canadian Amateur Radio Basic Qualification Study Guide (which I'm ...
BenAlabaster's user avatar
9 votes
1 answer
474 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?
natevw - AF7TB's user avatar
9 votes
2 answers
494 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 ...
koalo's user avatar
  • 399
9 votes
1 answer
227 views

Antenna size for wideband

I just bought a SDR dongle that comes with an antenna. The dongle is for DVB-T. The antenna is very small but the specs say that the dongle can go 30Mhz to 850Mhz. From my knowledge of antenna ...
Martin Naughton's user avatar
8 votes
3 answers
601 views

What is the permissible frequency error for US amateur radio transmissions?

What are my requirements as a licensed Amateur Radio operator in the US to keep to a single frequency? How much drift can I have during transmission and still be within my license? Does it depend on ...
Adam Davis's user avatar
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8 votes
1 answer
3k views

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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8 votes
4 answers
3k 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 ...
Alexander Churanov's user avatar
8 votes
2 answers
239 views

What will I need to receive the ICE/ISEE-3 transmitter?

The ICE/ISEE-3 spacecraft, launched in 1979, is due to pass by the earth in August, 2014. It was commanded to power down completely years ago, but it appears to have failed to do so, and while it ...
Adam Davis's user avatar
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8 votes
1 answer
854 views

Why are there no amateur allocations in the LF and VLF spectrum?

Amateur radio enthusiasts have slices of spectrum at every magnitude of spectrum MF and above, but in the US none are below MF. Why are there no spectrum allocations below 160M?
Adam Davis's user avatar
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8 votes
1 answer
2k views

Is the bandwidth of an LCR resonant circuit independent of the capacitance?

Is the bandwidth of an LCR resonant circuit independent of the capacitance, if the inductance and its series resistance are kept the same, and the Q is high? This question and the calculation ...
Harry Weston's user avatar
7 votes
1 answer
2k 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 ...
user avatar
7 votes
2 answers
4k 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 ...
eecs's user avatar
  • 159
7 votes
2 answers
806 views

Doppler Shift Compensation in Inter Satellite Communication

I am currently doing a project in the area of optical inter-satellite communication (GEO-LEO). I am using a optical carrier of 281 THz, and the Doppler shift corresponding to it is ±7 GHz. I ...
Seetharama's user avatar
6 votes
2 answers
547 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
  • 311
6 votes
3 answers
657 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
  • 610
6 votes
2 answers
259 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 ...
Hadad's user avatar
  • 325
6 votes
2 answers
9k views

Where can I find a listening guide for different frequencies and their usages to listen to on SDR?

I just got an RTL-SDR dongle by Nooelec and am using CubicSDR on Mac (which supports AM, FM, and SSB), and I'm in Canada. I'm able to easily find FM radio stations, but outside of that I'm not sure ...
user avatar
6 votes
2 answers
4k views

What are the default repeater offsets on 70cm in different countries? [closed]

I am looking for a reference list of the default repeater offsets by frequency and country on the 70cm band, to supply it into a radio control software. Most radios come with a list built-in, but the ...
Georg DO1GL's user avatar
5 votes
4 answers
3k 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 ...
kkris1983's user avatar
  • 153
5 votes
3 answers
8k views

What frequencies am I not allowed to use north of line A in the USA?

What frequencies can I not use if I live north of line A in the USA?
Timtech's user avatar
  • 2,336
5 votes
2 answers
1k 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 ...
YetAnotherRandomUser's user avatar
5 votes
3 answers
341 views

What are these antennas used for?

I noticed this antenna park in Heidmoosstrasse, Switzerland. What is it used for?
Loreno Heer's user avatar
5 votes
5 answers
935 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 ...
Derpy's user avatar
  • 95
5 votes
1 answer
644 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 ...
Christian Castellanos's user avatar
5 votes
2 answers
99 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 ...
Alex's user avatar
  • 183
5 votes
1 answer
325 views

Can I modify my radio to transmit on frequencies that I can currently only listen to? [closed]

I bought a radio that can receive 4 ham bands, but only transmit on 2. Can I modify my radio to transmit on these frequencies legally?
Timtech's user avatar
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5 votes
1 answer
1k 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 ...
user3141592's user avatar
5 votes
1 answer
1k views

Why does the ionosphere reflect some frequencies and not others?

Why is it that some frequencies transmitted at some known direction are reflected back to earth, yet others transmitted at the same direction, power and polarity pass through into space with no ...
BenAlabaster's user avatar
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
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
4 votes
2 answers
144 views

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
  • 255
4 votes
4 answers
2k 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 ...
Jack Amoratis's user avatar
4 votes
2 answers
769 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
  • 610
4 votes
3 answers
2k views

SSB demodulation

I was building the superhet receiver for ham radio. But I seem to have got stuck at the demodulation stage. As an example: Suppose the person is transmitting SSB signal (20m band) at 14.250 MHz ...
Plutonium smuggler's user avatar
4 votes
2 answers
391 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.
Hack-R's user avatar
  • 255
4 votes
1 answer
371 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 ...
Dave G's user avatar
  • 295
4 votes
1 answer
437 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
  • 610
4 votes
1 answer
138 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 ...
Thomas's user avatar
  • 734
4 votes
2 answers
712 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 ...
Josh's user avatar
  • 138
4 votes
1 answer
650 views

What determines the optimum frequency range for the transmission of signals?

What determines the optimum frequency range for the transmission of signals in a system that's transmitting electromagnetic signals between an antenna on the surface of the earth and an orbiting ...
Max's user avatar
  • 123
4 votes
1 answer
283 views

How can we determine what repeaters to use?

My wife and I are studying for our Technician class licenses. We are thinking about how we could communicate with each other while both of us are at work, she being in Oakland, CA and myself in ...
Jonathan's user avatar
4 votes
2 answers
972 views

Wouxun KG-UV6D PMR frequency "spillover"

So I recently bought a pair of Wouxun KG-UV6D. We don't have the license required to operate outside of PMR frequencies, but that's fine, as we will be using these for airsoft. The programming of 8 ...
David Skødt Lauritsen's user avatar
4 votes
1 answer
4k views

How many frequency channels are there in a frequency band?

I've often heard people saying that 4G uses the 1800 MHz band but precisely what all frequencies does it work upon? Does it mean that is just uses one frequency i.e. 1800 MHz, well in that case wouldn'...
Shivam Aggarwal's user avatar
4 votes
1 answer
237 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
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