Questions tagged [frequency]

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

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44
votes
5answers
4k views

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?
11
votes
2answers
700 views

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 ...
9
votes
4answers
32k 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?
9
votes
3answers
20k 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 ...
8
votes
3answers
420 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 ...
8
votes
2answers
281 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 ...
8
votes
4answers
1k 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 ...
8
votes
2answers
221 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 ...
8
votes
1answer
190 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 ...
8
votes
1answer
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 ...
7
votes
5answers
506 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 ...
7
votes
2answers
794 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?
7
votes
1answer
672 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?
6
votes
2answers
6k 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?
6
votes
2answers
2k 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 ...
6
votes
1answer
611 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 ...
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 ...
5
votes
3answers
3k 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?
5
votes
2answers
761 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
519 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
167 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 ...
5
votes
1answer
155 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 ...
5
votes
2answers
69 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 ...
5
votes
1answer
217 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?
5
votes
1answer
838 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 ...
4
votes
3answers
190 views

What are these antennas used for?

I noticed this antenna park in Heidmoosstrasse, Switzerland. What is it used for?
4
votes
1answer
252 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 ...
4
votes
3answers
1k 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 ...
4
votes
2answers
2k 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 ...
4
votes
1answer
162 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 ...
4
votes
2answers
786 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 ...
4
votes
1answer
2k 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'...
4
votes
2answers
71 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 ...
3
votes
3answers
579 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 ...
3
votes
3answers
130 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 ...
3
votes
2answers
8k views

Can a Baofeng UV-5R+ be used on FRS, GMRS, and MURS?

Is this secure if I was talking to another Baofeng UV-5R+?
3
votes
2answers
330 views

What are the technical reasons that there are no frequency modulated transmissions on the long- and medium wave?

Why are there no frequency modulated broadcasts on the long/medium/short wave, but only on VHF? I'm sure there are many historical and political reasons (long/medium/short wave were already in use for ...
3
votes
1answer
570 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 ...
3
votes
1answer
353 views

How can I tell the frequency without an oscilloscope, or frequency counter?

Just going through the RF oscillator listed on SM0VPO's web-site. I replaced C1 by a reverse biased 6A8, and used an E-core transformer pulled out of a Compact Fluorescent Lamp instead of an inductor ...
3
votes
0answers
93 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 ...
2
votes
3answers
344 views

What are the 3 or 5 peaks in an FM broadcast during silence?

Looking at the waterfall spectrum of any ordinary FM public broadcast station (88-108 MHz), during the silence, there are 3 or 5 visible peaks. What are they? It's possible this has a trivial ...
2
votes
2answers
2k views

Does antenna frequency matter when trying to pick up radio waves?

I'm buying the following: https://www.amazon.com/RTL-SDR-Blog-RTL2832U-Software-Defined/dp/B0129EBDS2/ref=sr_1_3?ie=UTF8&qid=1480215974&sr=8-3&keywords=RTL-SDR to analyze radio waves as ...
2
votes
3answers
2k views

Private Channel?

Is there a method to limit the people with access to a simplex channel? I would like to utilize a channel that is set up for just myself and my wife. If I gave directions to meet somewhere I would ...
2
votes
2answers
83 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. ...
2
votes
2answers
107 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 ...
2
votes
1answer
594 views

FM transmitter sending to multiple frequencies

I bought Veronica 1W FM Transmitter online, hooking it up and tuning the radio beside me, I can hear the audio on multiple 'stations' or frequencies. I've tried screwing the vc1 which the seller said ...
2
votes
3answers
587 views

Would a 2.4ghz yagi antenna work for Ham Radio?

I am building a miniature yagi antenna that is made for 2.4ghz. Would a 2.4ghz yagi antenna work for Ham Radio?
2
votes
2answers
2k views

Which Frequency Band(VHF/UHF) is most useful for satellite in MEO?

I want to get to know about the satellite communication at 8000-10000 km, During that, I come across the VHF and UHF. In that I am facing problem for deciding the frequency band for communicating with ...
2
votes
3answers
237 views

Is 2.4Ghz good for an UAV?

I'm designing a drone(UAV) as a hobbyist, and radio communications is not my strong point. I will be transmitting waypoints from a portable control station and receiving video(a low frame rate is ok). ...
2
votes
3answers
187 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 ...