Questions tagged [fm]

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

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62 views

What would cause 3 bursts of FM radio interference every ~3.5 seconds

I’m trying to locate the source of some interference on the FM band — it’s audible as 3 quick staccato bursts of brownish noise approximately every 3.5 seconds. It’s more pronounced at the low end of ...
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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 ...
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1answer
176 views

ICOM IC-910h How much bandwidth does it listen when receiving USB and FM?

CD-audio has a bandwidth of 22kHz. CW usually has a bandwidth between 3 to 5 kHz. But I am wondering what is the bandwidth my Icom IC-910H can listen to in both, the SSB and the FM mode? Also, what ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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103 views

Radio Waves propagation (Intuitive Understanding of Wave propagation)

I have few similar questions regarding Radio waves communication particularly FM and AM type of Radio wave communication. Please bear with the naivety of the questions. Questions: Radio waves in FM ...
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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,...
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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. ...
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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 ...
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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 ...
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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. ...
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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, ...
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3answers
113 views

Recommended Books For AM/FM (especially AM) Radio Design

I am trying to gain a better grasp of how to build an AM radio receiver. Can you direct me to some books (or other information) that will help?
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135 views

What determines the bandwidth of an FM signal?

With an FM signal, it takes up more room in the radio spectrum presumedly because the carrier frequency is changed. On average what's the width of the FM sidebands? Does the deviation from the center ...
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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 ...
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151 views

LA1185 FM downconverter shows weird behavior

I've built FM CCIR/OIRT downconverter based on Sanyo LA1185 IC. I've used most famous schematics for it with slight modification (added DC blocking capacitor 1 nF rated on the output) Coils L1 and L2 ...
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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 ...
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0answers
33 views

power limit on wireless FM microphone transmitters [duplicate]

I am building a "toy" radio station as a teaching tool for high school students to work with. I intend to use a small (short-range) wireless FM microphone module as the transmitter. What is the legal ...
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1answer
461 views

Frequency modulation with gnuradio

I'm trying to understand way which Frequency Mod block works in gnuradio. According to my intuition there should be at least two inputs: signal to encode base frequency / carrier signal Instead ...
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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 ...
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1answer
106 views

Radio antenna for my FM receiver / Android FM

I want to make a radio antenna at home which will be able to receive all FM frequencies for my FM radio or Android FM. How do I make it? Frequency it can catch : 88 - 108 MHz Thanks.
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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1answer
119 views

Ultrasonic FM receiver

I need a FM receiver that is capable of receiving ultrasonic audio frequencies above the standard wide band FM range of 15 KHz. I'd like something that can receive signals up to 60 kHz if possible: I'...
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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 ...
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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 ...
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1answer
173 views

Can a Harmonics from an Raspberry PI FM Transmitter Interfere with Emergency Bands?

One of my neighbors is an emergency personal and has a police radio at home so he knows when to respond. Anyways, the other day, I saw an article on MAKE on how to make a radio station with a ...
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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 ...
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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?
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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 ...
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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 ...
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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 ...
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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 ...
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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 ...
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290 views

Amplified antenna & typical boombox radio

Can an amplified antenna be connected to a typical boombox radio with a telescoping antenna without damaging the radio?
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94 views

Is there an advantage with having a DC bias for a FM radio transmission?

I'm studying FM radio transmissions at the moment. I'm using an NTX2B transmitter to experiment naturally assumed I'd use 0V for False/No signal and 3V for True. However, a lot of articles that I ...
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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?
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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 ...
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230 views

How to generate FM narrowband using varactors

I don't really understand how FM narrow band is created, and at the same time I can't figure out how using this simple circuit of varactors (varicap diodes) we narrow the bandwidth. simulate this ...