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Questions tagged [frequency]

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

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0 votes
1 answer
78 views

Is there a frequency pair appropriate for a temporary mobile 70cm repeater?

I am thinking about building a portable low power 70cm repeater for field and emergency operations. For example it could be placed up high on a mountain to cover the valley. Is there an appropriate ...
4 votes
0 answers
58 views

A first homebrew design: Band, antenna, and ground wave propagation

I'm working on a very simple homebrew transceiver and request review of our selected band, antenna, and power. Background: A child got very interested in ham radio, as an incentive for to earn his ...
0 votes
2 answers
387 views

Scanner radio purchase advice for someone that's nosy but not technological?

If it sounds like a stupid question, it probably is. My mom loves being nosy... When she hears the police siren, an ambulance, firefighters, or something like that, she's the first one to run to the ...
7 votes
3 answers
787 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: ...
0 votes
2 answers
178 views

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 ...
-1 votes
1 answer
74 views

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 ...
-3 votes
2 answers
152 views

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?
1 vote
1 answer
180 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 ...
3 votes
2 answers
48k 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+?
-1 votes
1 answer
1k views

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 ...
3 votes
3 answers
378 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 ...
1 vote
2 answers
328 views

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 ...
1 vote
2 answers
270 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 ...
0 votes
2 answers
81 views

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 ...
4 votes
1 answer
503 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 ...
0 votes
1 answer
112 views

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 ...
3 votes
3 answers
152 views

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 ...
-2 votes
1 answer
105 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 ...
6 votes
2 answers
685 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 ...
3 votes
1 answer
112 views

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 ...
4 votes
2 answers
151 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 ...
2 votes
4 answers
862 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 ...
4 votes
2 answers
541 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.
2 votes
2 answers
916 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 ...
0 votes
1 answer
177 views

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 ...
0 votes
1 answer
92 views

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 ...
0 votes
1 answer
688 views

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 ...
-3 votes
1 answer
218 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 ...
5 votes
1 answer
65 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 ...
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 ...
12 votes
5 answers
52k 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?
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?
1 vote
3 answers
173 views

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 ...
0 votes
3 answers
134 views

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 ...
51 votes
5 answers
9k 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?
12 votes
2 answers
2k 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 ...
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 ...
1 vote
1 answer
145 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 ...
8 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 ...
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'...
0 votes
0 answers
793 views

How to shift frequency with sine signal?

cosine signal can make square signal shift frequency. If I have only sine signal source,how ...
2 votes
2 answers
327 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 ...
-3 votes
1 answer
459 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 ...
0 votes
1 answer
73 views

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(...
2 votes
1 answer
214 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,...
2 votes
3 answers
466 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. ...
1 vote
4 answers
353 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 ...
6 votes
2 answers
936 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?
1 vote
4 answers
7k 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 ...
6 votes
2 answers
278 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 ...