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

It's a feature not a bug. When turned on, the weather alert function checks the local NOAA station for its alert tone every 5 seconds for half a second... doing so takes over the receiver. I'd turned ...
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15 votes
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Why do we not use AM and FM at the same time to transmit more information?

QAM modulates both the phase (= frequency) and amplitude of the signal.
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13 votes
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Resort FM radio station

I believe you have encountered a Part 15 radio station. United States Code of Federal Regulations, Title 47, Part 15 (47 CFR 15) covers such things as garage door openers and the like. As such, ...
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13 votes

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

It turns out that we DO simultaneously use frequency and amplitude modulation: our everyday term for this is "single sideband." As described on Wikipedia, single-sideband is a special case of ...
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12 votes
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Single Side Band AM vs FM

First of all, you're not 100% right that SSB will reduce transmit power. I often keep talking on SE about power spectral density. So let me start with that again and first assume that we have a ...
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12 votes
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Understanding WFM modulation

Your “B” is the stereo difference signal of broadcast FM stereo. It is placed at twice the pilot frequency so that it can be recovered by having the receiver lock onto the pilot signal and frequency-...
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10 votes

How do VHF antennas compensate for change in frequency in Frequency Modulation?

All modulated signals, not just FM, have a bandwidth. The antenna has a bandwidth, which must be wider than the modulation of the signal you are using. Note that receive bandwidth and transmit ...
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9 votes

Single Side Band AM vs FM

Firstly, FM is a constant-envelope modulation, meaning the amplitude is constant. SSB, being a kind of amplitude modulation, obviously does not have a constant amplitude. Consequently, FM can employ a ...
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8 votes
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How does FM encode BOTH amplitude and frequencies of full audio signal spectrum?

Whatever modulation we use, there's a baseband signal we wish to transmit (music, voice recording, whatever), which somehow modulates a carrier to produce the output signal. Your question suggests ...
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8 votes
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Can two FM radios transmit two separate PL tones at the same time, and be received by two radios with matching PL tones?

Assuming that the two transmitters operate at the same carrier frequency, and that the receivers receive similar power from each transmitter, then the FM signals will suffer destructive interference ...
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8 votes
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Is it legal to transmit with HackRF one?

You'll need an experimental radio license (Versuchsfunk) from Bundesnetzagentur link for research operation. For demonstration/teaching purposes, a demonstration radio license (Demonstrationsfunk für ...
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8 votes

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

The story is about Eric LeMarque who got lost after snowboarding out of bounds in the Sierra Nevada mountains. Radio receivers usually contain some kind of oscillator. Detecting the unintentional ...
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8 votes
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How does FM station have fixed frequency when FM modulation changes the frequency?

"Tuning" an FM receiver sets the center frequency of the receiver, but its internal circuitry is designed to pass enough of the Bessel sidebands produced by frequency modulation of that waveform to be ...
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7 votes
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What are the technical reasons that there are no FM transmissions on the long, medium, or shortwave?

So, the bandwidth argument is the dominant one. You need to incorporate the full Carson Bandwidth in your channel spacing, not only the frequency deviation! As explained in my answer to your previous ...
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7 votes
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Sound quality in portable FM radio devices vs dedicated stations

Bandwidth: Broadcast FM stations are spaced 200 KHz apart, with the intention of allowing this kind of signal structure without interference: The FM broadcast bandwidth of just more than 50 KHz is ...
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  • 2,021
7 votes

Is it legal to transmit with HackRF one?

As for other legal alternatives, one might be transmitting inside a suitably shielded Faraday cage. I’ve seen such facilities at labs where various prototype and pre-production (and competitors?) ...
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7 votes

How do VHF antennas compensate for change in frequency in Frequency Modulation?

Or does this antenna have a frequency tolerance? This is closest, but the antenna, itself, does not actually have a “frequency tolerance” (more usually called a bandwidth). Rather, the antenna's ...
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6 votes

Any SDR radios that receive FM BCB

Almost every SDR receiver is capable of receiving the FM broadcast band. The ones which can't are typically SDR transceivers designed for specific HF bands. The harder part of your requirements is ...
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6 votes

What does multi-path sound like on FM?

Multipath distortion can be problematic on fast digital modulations since the receiver sees multiple copies of the transmitted signal, each delayed by some appreciable fraction of a symbol. For ...
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6 votes

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

This is a link budget question. Transmit power is just one factor: others are terrain, antennas, frequency, quality, noise, and so on. If we restrict the variables to typical values for FM commercial ...
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6 votes

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. Under certain conditions, that is! Namely, additive noise, and a fading channel. or is this ...
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6 votes

FM radio demodulator IC usage

So, coming at this from an engineer's perspective: If a device has a datasheet that doesn't tell you how to use it, it's not the device you need – end of story. So, by the way, ebay searches aren't ...
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6 votes
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FM radio demodulator IC usage

...I don't know what I am supposed to connect to the input... Am I expected to frequency shift the signal from the radio station down to whatever the chip may support... Several of the ...
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  • 7,685
6 votes

FM radio demodulator IC usage

That AN7411 is not an FM demodulator. It's a stereo demodulator, taking audio (0 to 57 kHz) from an FM demodulator, recovering the stereo multiplex signal (DSBSC at 38 kHz carrier), adding that (L - ...
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6 votes
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How do VHF antennas compensate for change in frequency in Frequency Modulation?

Most VHF+ antennas are not that narrow banded. They usually have a low enough Q. Thus, there is usually no need for a tunable antenna. Also, antennas are generally not any different regardless of the ...
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5 votes
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FM squelch SDR algorithm?

The simplest squelch, applicable to almost all modes, and the one provided by most amateur radios' “squelch knob” as far as I've experienced, is power squelch: measure the signal power (in SDR, $I^2 + ...
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5 votes
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How do PL tones make it through so much noise?

As Michael noted, a repeater's CTCSS system is looking for a very specific frequency with a very low deviation (typically 10% or less) as low as about 40 dB down. What you are hearing is of course ...
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5 votes
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How can I make WBFM receiver without using WBFM Receive block?

General principle: In GNU Radio you cannot ever have a flow graph with a loop in it. If you wish to have feedback of some kind, it must be implemented in a single block. (There are many existing ...
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5 votes
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Why does SDR# sound better than SDR console?

I'm not familiar with the behavior of the particular programs you've named, but the obvious (guessed by ear and confirmed with a spectrogram/waterfall tool) difference between these two clips is the ...
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5 votes
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What are the practical differences between the different voice modes (and why aren't there any SSB Handheld Transceivers (HT's))?

SSB phone requires good frequency stability to be intelligible. Anything over 10Hz of frequency difference between transmitter and receiver and the signal starts to sound funny; beyond 50-70 Hz of ...
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