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Questions tagged [modes]

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

6
votes
3answers
106 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 ...
0
votes
2answers
63 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
votes
2answers
66 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
votes
1answer
50 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
vote
1answer
63 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?
1
vote
1answer
58 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 ...
3
votes
2answers
110 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 ...
1
vote
1answer
72 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 ...
3
votes
3answers
194 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 ...
4
votes
2answers
300 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 ...
1
vote
1answer
250 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
votes
2answers
262 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 ...
7
votes
1answer
779 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 ...
0
votes
1answer
688 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 ...
1
vote
1answer
326 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 ...
2
votes
2answers
211 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 ...
1
vote
1answer
60 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
vote
1answer
111 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 + ...
1
vote
2answers
80 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 ...
6
votes
2answers
379 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'...
5
votes
2answers
103 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 ...
2
votes
3answers
123 views

Which mode describes this modulation scheme

I have a modulation mode: (to be used for a satellite) (of a series of AX.25 frames) (in the 70 cm band) 9.6 kbps Ideally BPSK or QPSK modulation but could be plain FM Which I need to describe with ...
1
vote
1answer
878 views

How to identify type of modulation based on constellation diagram?

The constellation diagrams for a 4-ary modulation using PSK (qpsk),MSK ,QAM and OQPSK look alike. How to differentiate them? What is the modulation for the constellation diagram in the figure?
1
vote
1answer
135 views

SSB Modulation and Differential Signaling

I'm trying to learn about how SSB modulation works. My current understanding from reading and looking at spectrum plots from SDR software is that the sound is modulated with the carrier, but only ...
3
votes
2answers
248 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 ...
0
votes
2answers
775 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
vote
2answers
184 views

Software TNC's for Linux? (targeted to BPSK1200)

Are there any software TNC's (like SoundModem) for Linux? This is limited to the ones which deal with BPSK1200 (used by cubesat projects). For some cases Warbler will suffice.
4
votes
1answer
203 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 ...
3
votes
1answer
2k views

Why there is no AFSK in FLDIGI

I was expecting to see an AFSK option in FLDIGI "Op Mode" menu (as there is one option for CW, i.e.), why it isn't there? Basically, I want to get the data send according to this.
2
votes
1answer
260 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 ...
2
votes
2answers
334 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 ...
3
votes
1answer
2k views

Comparision between BFSK and BPSK

Why is BPSK preferable over BFSK? On what parameters this comparison is based? What are the advantages of BPSK?
6
votes
4answers
519 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 ...
7
votes
1answer
253 views

Why does AM have sidebands?

Why does AM have sidebands? Isn't the whole point of AM to broadcast on ONE frequency and ONLY change the amplitude? In the picture there is only ONE frequency and the amplitude changes, so why ...
6
votes
1answer
557 views

Video transmission between ATV and SSTV

I'd like to experiment with amateur video transmission in a setup halfway between ATV and SSTV. 480 lines of B&W image would be sufficient with 10 FPS, and I'm interested in both digital and ...
1
vote
1answer
291 views

WFM SDR and Audio resolution

How does SDR resolution translate to audio resolution when using an FM demodulation algorithm? For example: using a 8-bit/2.048 Mhz IQ stream, what is the maximum audio sample rate and bit depth that ...
2
votes
0answers
283 views

How did recording ZX Spectrum games from radio work? [closed]

I have recently heard about recording video games' binary codes from radio programmes which was quite popular several decades ago. The computer name was ZX Spectrum. The general idea behind the ...
2
votes
3answers
167 views

Multiple transmitters using same frequency

in our wireless network we have a variable count of devices. Each device contains one transmitter and receiver. Both receiver and transmitter are working on the same frequency, 433 MHz. To keep the ...
1
vote
1answer
39 views

Determining modulation by spectrum

Is it feasible to determine what sort of modulation is used for a given signal by looking at the spectrum / FFT? Does software like this exist?
3
votes
1answer
104 views

Up converted audio transmission

I was thinking about all the different modulation methods and something came to my head. After seeing up converters that convert HF to VHF for SDR (software defined radio) dongles to be able to listen,...
4
votes
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 ...
6
votes
1answer
921 views

What should be the modulation when transmitting APRS signal?

Is it SSB or NFM or other type of modulation?
7
votes
1answer
1k 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.
3
votes
2answers
317 views

How can I know over what distance or at what speed I can communicate? [closed]

Given some description of some parameters like: transmitter power frequency antenna location time of day how can I know over what distance communication is possible? Can I know the limits to these ...
5
votes
2answers
180 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 ...
2
votes
1answer
165 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 ...
1
vote
1answer
83 views

Can I filter after modulation when using a square wave oscillator? [closed]

Most designs appear to filter most of the harmonics out of the oscillator before modulation, then apply additional filtering as needed for the specific modulation they are using after modulation. ...
4
votes
5answers
1k views

What about the digital mode ROS causes some to consider it spread spectrum?

The FCC disallows amateur spread spectrum communications below 220MHz. At the moment the relatively new digital mode, ROS, is considered, by some, to be spread spectrum. So this mode is getting ...
4
votes
1answer
380 views

What is this short, wide band signal?

I've observed a signal I'm unfamiliar with, and am wondering what it might be: The period of time it lasted is 5 seconds, and it occurs irregularly. You might be able to see it too via WebSDR. How ...
5
votes
2answers
102 views

Is CW necessary to be competitive in most ARRL contests?

The ARRL hosts many contests throughout the year, and maintains a leaderboard of sorts to encourage competition. Is it possible to rank on any of the leaderboards without knowing or using morse code?