Questions tagged [modes]

Questions related directly to the mode of communication (SSB, CW, digital, etc).

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2
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2answers
109 views

Would Orbital Angular Momentum (OAM) multiplexing work over HF bands?

OAM (Orbital Angular Momentum) Multiplexing is a form of multiplexing capable of high data speeds on limited bandwidth using the physical properties of EM waves. An experiment in 2012 transmitted two ...
2
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0answers
61 views

Is this signal BFSK or BPSK?

I'm trying to analyse a signal from a HVAC remote control (864 MHz) with my HackRF, but I'm facing an interrogation about the used modulation: Is it BFSK (frequency modulation) or BPSK (phase ...
0
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2answers
121 views

Why can I hear Morse when not in CW mode?

I don't "get" CW. I can't understand the chatter on an FM radio broadcast when my radio is set to AM. This makes sense, the signal is modulated using frequency modulation and I am trying to ...
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0answers
27 views

2GFSK digital filter bandwidth calculation

I'm working on a S2LP from ST and I am configuring the RX digital filter. I need to calculate the bandwidth of the signal which has 2GFSK modulation. Do you think the code below is correct for ...
2
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1answer
169 views

What would be a good modulation scheme for communicating a single bit of information with no more than 4ms of latency?

This question has been suggested in the comments to a closed question a couple of days ago. I have nothing to do with the original question, but this aspect of the problem made me quite curious, so it ...
3
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3answers
100 views

NFM and FM compatibility

I read that using narrow band (NFM) when you should be using normal(FM)/wide-band(WFM) can result in the a reduced volume at the receiver. What happens in the opposite situation? (What if you are ...
4
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1answer
3k views

Why doesn't GNU Radio Companion's wx Constellation Plot doesn't give me the clean QAM constellation I get from its Qt sibling?

Using a RTL2832U USB dongle, I set up GNU Radio to produce a constellation plot of APRS traffic on 144.8 MHz. The result is what I expected: So far, so good. Why not try the same thing using the wx ...
0
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1answer
53 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 ...
4
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1answer
117 views

Is it practical to use a magnetic amplifier as an AM modulator in a transmitter?

If I'm building a vacuum tube HF transmitter (say, 40 m band), obviously the simplest mode to build is CW; it's common to key the oscillator input to the final (in order to keep the oscillator running ...
10
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6answers
224 views

Practical limits to maintaining coherence in an HF channel

Lately I've been thinking about weak signal communication on HF. Very weak, like weaker than even WSPR could achieve. It would be nice if one could simply take any existing modulation and slow it ...
0
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1answer
46 views

Both OOK and FSK used in the same transmission

My gas burning heating unit takes its temperature readings from a 433 MHz thermostat, which is emitting precisely the same data packets in a packet train at some ~100 ms interval like this: 2 x OOK ...
6
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2answers
75 views

Can an ultra-wideband system transfer data at high speed without precise clock synchronization?

Recently, ultra-wideband technology has been in the news again. From the Wikipedia article: UWB transmissions transmit information by generating radio energy at specific time intervals and ...
2
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3answers
158 views

Is double amplitude modulation useful?

If i amplitude modulate an AM carrier with an audio signal, can i then feed that resultant AM waveform into another modulator and amplitude modulate the AM signal to give a signal which is amplitude ...
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3answers
379 views

Is it possible to have multiple people talking on the same radio channel at the same time?

I understand that my question is not desireable for ham radio communication at all, but bear with me. I want to use long range walkie talkies whose microphone is attached to an underground acoustic ...
60
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16answers
7k views

Why is Morse Code still in use?

Why do people still use Morse Code? What are its advantages over newer Voice or Data communication modes?
4
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1answer
3k views

Why there is no AFSK in FLDIGI

I was expecting to see an AFSK option in the Fldigi "Op Mode" menu (as there is one option for CW, i.e.), why isn't it there? Basically, I want to get the data send according to this.
2
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2answers
401 views

BPSK raw data aquisition with HDSDR and FLDIGI

I was playing with HDSDR+ExtIO and Ettus USRP1 to track a BPSK signal. In the end I successfully heard the signal. But I would like to see the data, I mean the raw data (HEX values). For that I tried ...
7
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4answers
941 views

Is frequency hopping a viable solution for privacy and security without encryption?

In terms of radio transmission, three major issues seem to arise for various sensitive transmissions: Others do not gain access to the content of the message Others cannot determine the location of ...
5
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2answers
876 views

How does rpitx generate arbitrary SSB data with a clock peripheral?

While it wasn't the first to do so, the rpitx software seems to be the most active and mature implementation of what its own comments call "a code fragment by PE1NNZ". The trick is explained in Guido'...
7
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3answers
1k views

What exactly is a “balanced modulator”?

While studying for his U.S. General class license, my son wondered about the "balanced modulator" referred to by a few questions in the FCC pool. Quoting KB6NU's General Class study guide to give a ...
4
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1answer
224 views

Warbler vs SoundModem

I'm trying to decode a BPSK 1200 (with no success). In this endeavor I tried both SoundModem and Warbler. The scenario here is the following: Ettus receiver + HDSDR with speaker plugged into mic via ...
5
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4answers
465 views

Is there such a thing as a phase modulation voice signal?

Wikipedia indicates that in the digital domain ASK, FSK, and PSK are common. It seems that only AM and FM are used for analog forms of communication. Why don't we use Phase Modulation techniques, ...
0
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2answers
193 views

Peak envelope power should be 2:1 or 4:1 on meter?

I've always been reading my AM modulated signal on a Bird wattmeter and trying to set the carrier to 1/4 of the peak envelope power (PEP). Recently, I was told by a CBer that you only can see it that ...
0
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2answers
85 views

How to decode a message with unknown bit rate in interstellar signal

I have a question about FSK modulation I'm going to frame in terms of a hypothetical: Imagine that you are transmitting a message to an ET in another solar system. The message is encoded in binary ...
3
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1answer
344 views

How/where can I learn about ft8? [closed]

Where can I find information about the digital modes and how to get started on them? I would like a concise yet easy to understand tutorial.
1
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1answer
123 views

Parts for a 915 MHz low power transmitter

I'm interested in doing some experimentation with custom modulation in the 915 ISM band. Off-the-shelf radio modules use specific known modulations (FSK, QAM, etc.) so those won't work for my ...
10
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3answers
401 views

Does modulation affect propagation?

Does the modulation scheme, whether OOK, SSB, AM, FM, a digital mode, etc, affect the propagation of a signal?
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1answer
228 views

What are all the three letter codes for the different emission designators?

For example, A1A is "morse telegraphy by on-off keying". What are the others?
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1answer
64 views

Why AM modulation side bands have higher frequencies than the carrier?

I cannot understand while the AM modulations have sidebands which are of a frequency higher than the carrier. If for example we are modulating a 4kHz signal to a carrier of 1MHz how we end up with a ...
2
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1answer
181 views

What modes are used for transmitting motion pictures video?

SSTV permits transmission of single images, or if one desires image sequences at a very low framerate. Are there specific Amateur Modes that are meant for real time (motion pictures) video ...
6
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2answers
424 views

Is it possible for an amateur to transmit ATSC?

Amateur television has long used the NTSC (analog) television standards to transmit video and audio. Several years ago, the digital broadcast television transition made higher-quality television ...
2
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2answers
267 views

FSK or M-PSK for weak signal communications?

Popular amateur radio "below-the-noise-floor" communication modes (such as JT65, et.al.) seem to mostly use FSK, whereas NASA's deep space network appears to use M-PSK for (extremely) weak signal ...
3
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2answers
360 views

How to reverse engineer a proprietary FSK protocol

Assuming I wanted to reverse engineer 13FSK, what steps would I take to begin reverse engineering it? I have seen tools such as inspectrum and baudline that can help me view the raw signals, but I am ...
3
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2answers
662 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
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3answers
447 views

Why are carrier waves necessary?

I am studying for the technician exam and I have come across the section on carrier waves, basebands, and various kinds of modulation. It makes sense to me that you create a signal by combining the ...
1
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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 ...
3
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2answers
377 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 ...
11
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2answers
951 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 ...
5
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2answers
212 views

Frequency Modulated Light

I've been doing a bit of work on optical open-air transmission, and have been thinking, any hays that varies the intensity of the light or whatever else would affect the amplitude. Would it be ...
9
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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 ...
2
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2answers
239 views

(HF) How to maximize probability of successful transmit given constrained packet duration? [closed]

I need a HF link that will be (mostly hah) operational 24/365. Edit: at least at local daytime. The link is supposed to transmit a controlling signal (just one bit) in one direction for quite a ...
0
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1answer
1k views

LoRa Radio RFM96/98 SX1276/8 configuration settings for Longest Range

I have a pair of HopeRF LoRa RFM98 Radio Modems(based on Semtech SX1278) and I want to configure them for the longest range possible, without taking care about any second factor like transmission time ...
2
votes
1answer
334 views

Can HDSDR perform the work of Direwolf?

I have a setup in which Direwolf is used in conjunction with a Baofeng radio to basically send data (AFSK). My app connects to the TCP server provided by Direwolf, send him some data which then is ...
0
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2answers
941 views

What is Digital Mode on newer HF Transceivers

What does switching to digital mode on Yaesu Xcvr's (or any other HF radio) actually do? The documentation states that "specific digital mode selections, which include custom BFO offsets to optimize ...
1
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1answer
497 views

How does a transceiver work?

I recently joined my university's Cube-Sat Program and was delegated the task of looking for software that modulates and demodulates signals (~437MHz, GMSK, AX.25). The problem now is that I don't ...
1
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1answer
92 views

overly large bandwith for a FSK signal?

I am trying to recover my 2FSK signal using an SDR. I have centered the SDR modem on the median frequency (the virtual carrier) and captured my signal via some 90 kHz bw modem. THis is the recording ...
1
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1answer
201 views

transmitted FSK, sniffed something PSK-looking

I am transmitting a FSK signal on 433,941 ± 32 kHz at 19200 baud rate. From what I read I should be able to recover my signal with a a modem centered on my carrier and having a bandwidth of 32 × 2 + ...
12
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3answers
583 views

What is the role of digital data modes in emergency communications?

Emergency operations are typically reliant on voice traffic today. Are digital data modes used at all in emergency operations, and why/ why not? Couldn't data modes be used to pass information more ...
1
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2answers
89 views

different digital modulations interference. Does it happen?

Bottom line is I have got a very strange (but regular) reading on a < $1 type of ASK 433 MHz receiver. Have a look at it - those 3 spikes are sometimes caught by my receiver, don't know their ...
5
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2answers
142 views

Air gapped digital communications mode on VHF?

According to this question MCW (modulated continuous wave) is allowed on large portions of the VHF bands in the U.S. Is using MCW suitable for passing small amounts of digital data between 2 PCs or ...