Questions tagged [fm]

Questions about Frequency Modulation, the analog modulation scheme commonly used for voice on VHF and UHF frequencies.

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16
votes
3answers
5k views

Why do we not use AM and FM at the same time to transmit more information?

Amplitude modulation uses the modulation of the amplitude of a carrier wave to transmit data while leaving the carrier frequency constant, and in the case of FM it's just the other way round. Why is ...
13
votes
1answer
3k views

Why does the audio on my FM transceiver cut out every 5.5 seconds?

Specifically, my Icom ID-4100a. What's interesting, is that this happens in MR and VFO modes... but NOT when using the built-in WX stations. For example listening to WX-01 (162.550 MHz), no problem. ...
12
votes
3answers
557 views

Resort FM radio station

I stayed at a resort in the U.S. recently that is located in an unpopulated area with virtually no radio reception. To fill the gap, the resort has its own FM station that can be heard only within ...
11
votes
1answer
1k views

Is FM modulation still more resistant to noise when given the same bandwidth as an AM signal?

FM modulated radio is much more resistant to noise and can deliver better sound quality than AM radio. But FM signals also use more bandwidth than AM signals. In general a wider bandwidth signal is ...
9
votes
3answers
2k views

Is it legal to transmit with HackRF one?

Is it legal to transmit using HackRF one (in Germany), the purpose is to do some Lab research and Academic experiments. for example i want to broadcast an FM signal using HackRF one and try to ...
9
votes
1answer
2k views

How does SDR demodulation differ between wideband and narrowband FM?

What is the difference between software demodulation of an IQ signal between wideband FM and narrowband FM? Both seem to look at the 2nd difference in unwrapped phase angles of IQ samples.
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 ...
7
votes
3answers
7k views

Single Side Band AM vs FM

I know the difference between AM and FM, but could anyone explain to me what is the differences between single side band AM and conventional FM? So far as I know the SSB modulation will reduce the ...
7
votes
2answers
846 views

How does FM encode BOTH amplitude and frequencies of full audio signal spectrum?

How does frequency modulation encode both amplitude and frequency of the modulating audio signal only by varying frequency? How do both components get spread across and encoded in the side bands? I ...
7
votes
1answer
439 views

Is FM appropriate for foxhunting?

I'm thinking about an inexpensive way to create a foxhunt kit for youth groups, and am wondering if the cheap dual band HTs could be used. However, it occurs to me that FM doesn't provide any good ...
6
votes
5answers
6k views

Are there any commonly used digital modes that work with an FM transceiver?

Like many new hams, I have just one radio: an inexpensive 2m/70cm FM transceiver. It doesn't do SSB and it doesn't have a digital input. If I wire up a connection between the radio and my computer's ...
5
votes
2answers
4k views

What does the term 3 kHz deviation relate to in the FM world?

I am confused when someone says "your audio levels are set right and has good deviation at 3 kHz" when talking about wide-band 25 kHz FM signals. First confusion: Why are audio levels measured in ...
5
votes
1answer
256 views

Receiving commercial / public-safety on a general-coverage HAM transceiver

I have an ICOM-7100 that I've installed in my mobile as my primary (nay, only) HAM transceiver; and I'm trying to avoid wasting a ton of space in my vehicle (not to mention money) for a proper scanner,...
5
votes
1answer
194 views

FM spectral amplitudes during silence

General setting I'm playing around with an RTL-SDR and recently captured some FM spectrum in Hannover, Germany. I want to undersand what's going on, so I've read a lot about FM and its spectra, but I ...
4
votes
3answers
653 views

What are the technical reasons that there are no FM transmissions on the long, medium, or shortwave?

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 ...
4
votes
2answers
820 views

Sound quality in portable FM radio devices vs dedicated stations

When speaking to a portable radio transmitter the sounds usually gets distorted. However in radio stations that are dedicated to play music the sound is significantly better. First of all, why? And ...
4
votes
4answers
3k views

What does multi-path sound like on FM?

I know I have probably experienced multi-path propagation on FM modes when I was working a repeater in the grand canyon and in the mountains. How can I identify when I am getting multi-path, and what ...
4
votes
2answers
83 views

Can a phase-modulated voice radio transmission be received and heard properly by an “FM” radio?

Not necessarily an amateur radio question (but perhaps a licensed amateur should know the answer?) - I note that the specifications for marine VHF radio operating in the 156-157 mhz band call for both ...
4
votes
4answers
4k views

What are some equivalents of a BF199 transistor?

I'm planning to build an FM radio receiver using the instructions on http://www.instructables.com/id/Build-your-own-Crude-FM-Radio/ The schematic uses a BF199 transistor which is marked "obsolete" by ...
4
votes
1answer
933 views

FM squelch SDR algorithm?

What signal characteristics in an SDR receiver signal path should be evaluated or computed to determine whether the audio output should be squelched or not? What sort of computed result should be ...
4
votes
2answers
715 views

Yaesu FT-991A: FM and C4FM modes don't work on HF bands

I bought a second-hand Yaesu FT-991A. It works pretty well and by the look of it's internals I don't believe it was ever repaired. However I noticed one weird thing. When I try to use FM or C4FM on ...
4
votes
1answer
843 views

How to make an inductor?

I am a high school student and am making a project on FM receiver for class 11. I am following this circuit diagram: The L2 in this diagram is a 22µH RF Choke. The part listed in the website has the ...
3
votes
2answers
1k views

How does FM station have fixed frequency when FM modulation changes the frequency?

I am not sure if this question fits better in physics.stackexchange or ham.stackexchange, feel free to correct me. I am new to studying RF and SDR in general, I was looking up how modulation works and ...
3
votes
2answers
893 views

Understanding WFM modulation

I am using "HDSDR" software to demodulate a WFM broadcast ("Classic FM" in the UK, on 100.1 MHz, 192 KHz bandwidth). I'm using an "SDRPlay RSP1" software defined radio and a cheap indoor discone ...
3
votes
3answers
860 views

Any SDR radios that receive FM BCB

Are there any software defined receivers capable of receiving Regular FM broadcast band stations and displaying a waterfall of the band from 88 MHz to 107 MHz or a significant portion of that range?
3
votes
2answers
426 views

Can two FM radios transmit two separate PL tones at the same time, and be received by two radios with matching PL tones?

Can two FM radios transmit two separate PL tones, and be received by two radios with matching PL tones? Or will the receivers hear a mix of the two, or nothing at all?
3
votes
1answer
167 views

How do PL tones make it through so much noise?

So sometimes I hear people trying to get into a repeater with pure noise, and no audible audio on their transmission. With the repeaters that require a PL tone, how can the PL tones get through all ...
3
votes
1answer
265 views

GNU Radio - Frequency parameter of Signal Source Block

I designed an analog FM transmitter with GNU Radio Companion in order to understand the tool better. The hardware I use is an USRP B200. The carrier was built with a Signal Source block and the ...
3
votes
2answers
928 views

What's the difference between the normal and S-meter squelch in IC-2730?

I recently obtained an IC-2730E and can't figure out the difference between its squelch options. Unfortunately, the user manual isn't very helpful. The squelch option had 3 types: off, attenuation and ...
3
votes
1answer
2k views

Why are FM radio waves less susceptible to interference than AM?

When studying modulation of radio waves (or of most electromagnetic waves for that matter) I came across this question: Why are FM waves less susceptible to interference than AM waves? I know that ...
3
votes
1answer
182 views

FM carrier wave frequency determination

I know the difference between AM and FM, but how does a receiver determine the carrier wave frequency, as the frequency edited during the modulating process?
3
votes
1answer
318 views

How to generate FSK with Matlab and radio

I want to generate an FSK signal with a radio. My first idea is to generate an audio in which the high level is a 1 and the low level is a 0: This audio is then modulated by the radio with FM. In ...
2
votes
2answers
1k views

Can a FM tuner (receiver) be detected and triangulated?

In movie "6 Below", based on a true history, a lost snowboarder at Mammoth Mountain (California) is located by search and recuse when they detect and triangulate a signal from his MP3 player that also ...
2
votes
3answers
679 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

How far does a watt equal in range in the FM band?

How many watts would be needed to cover a 10 mile radius with good sound for music on the 88-108 MHz FM broadcast band? I am an amateur and for fun only.
2
votes
1answer
136 views

Receiving an Coded Odd Signal at 137.25MHz but don't know what it might be. It can affect my detection on NOAA 19. Need help

I am a newbie trying to detect NOAA 15, 18, and 19 satellites, which have downlink frequencies between 137 MHz and 138 MHz. I am using an SDR dongle and attached a photo of it to this post. Of course,...
2
votes
1answer
312 views

Why does SDR# sound better than SDR console?

This is kind of odd. I just got my first SDR receiver and I noticed that one application (SDR#) sounds a lot better than another (SDR Console) when listening to stereo FM broadcasts through the same ...
2
votes
1answer
1k views

How can I make WBFM receiver without using WBFM Receive block?

I'm trying to make a WBFM receiver without using WBFM Receive block. So I've tried this way But it won't work. The problem is RuntimeError: flow graph has loops! and I need to use loop feedback ...
2
votes
2answers
696 views

Bad squelch on a TYT MD-380: user error or hardware?

I have a new TYT MD-380; it works well for DMR channels, but on analog, the squelch doesn't seem to open when it should. I'm relatively new to ham and my first suspicion is user error, but it's ...
2
votes
1answer
93 views

Buzzing FM interference

What kind of interference or other receiver issues can cause a constant buzzing noise (picket fence lines in the audio spectrum) in the demodulated audio of a received NFM VHF signal? With AM, it ...
2
votes
3answers
101 views

Store and forward system like voicemail for hams

I want to be able to get in touch with hams in my area when we are not both on air at the same time, but are close enough to each other for VHF communication. I want to be able to use my radio to call ...
2
votes
1answer
3k views

Can I convert a telescoping antenna radio to work with an FM Dipole?

I have an older FM Radio with a telescoping antenna. Is it possible to convert that to work with an FM dipole antenna to get better reception? Such as this one. Preferably without any soldering. (I'...
1
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3answers
1k views

FM radio demodulator IC usage

An Ebay search for "fm demodulator" results in a whole slew of ICs, but even after reading their datasheets, I have no idea what I should connect where and what input signals the chips will work with. ...
1
vote
3answers
102 views

Modulation basics

I have a new interest in RF modulation and read the O'Reilly book electronics cookbook. I understand that in FM you start out with a carrier wave and then it is modulated but I don't understand if ...
1
vote
2answers
152 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 ...
1
vote
2answers
96 views

What are the practical differences between the different voice modes (and why aren't there any SSB Handheld Transceivers (HT's))?

It's my understanding that FM is used for UHF, VHF, and SSB is generally reserved for other bands. From my understanding, FM better audio quality when reception is good SSB: more efficient (can ...
1
vote
3answers
142 views

Need antenna for mobile mag-mount LPFM broadcast 88.3 MHz

I am doing some temporary FM broadcasting for car events such as COVID-safe car parades and drive-in movies. The terrain is horrible, urban areas with lots of buildings. The cars snake around a city, ...
1
vote
2answers
923 views

Pre-emphasis measurement

I am researching a way to build a pre-emphasis circuit, so I looked up the specs for different pre-emphasis standards. An example is the standard for FM broadcast, in the USA it's 75 µs. I am ...
1
vote
2answers
597 views

What is the essential gear to have in a VHF/UHF FM base station? [closed]

I'm trying to assemble a VHF/UHF FM base-station at home. Assuming I have the following pieces of equipment: VHF/UHF FM transceiver power supply - 30 amps, no meters antenna that's resonant on 2m and ...
1
vote
1answer
1k views

What is the FM-N mode?

I'm reading the Icom IC-51E PLUS2 manual and it says it supports the following modes: AM FM FM-N DV What is FM-N? I'm new to amateur radio and never heard of it before. It's not listed on Wikipedia ...