Questions tagged [transmitter]

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11
votes
4answers
7k views

How To Join Packet Radio BBS

I'm a complete newbie here, and on the Southeast Coast of the USA. I don't even own a ham radio yet. Some preppers and I got to talking about a dystopian time of Internet collapse where shortwave ...
10
votes
3answers
873 views

What does the spark-gap do in a spark-gap transmitter?

I read the Wikipedia article about spark-gap transmitters and I have to admit that I’m even more confused as to what the spark-gap actually did. The article references this simplified circuit ...
8
votes
4answers
964 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 ...
6
votes
3answers
193 views

Long range communication with just 1W of power?

Is it possible, and how can I setup communication between stations 1000km apart from each other by using just 1W of transmission power? By communication, I mean: It can be text based It can be very ...
6
votes
2answers
2k views

Preventing CW key clicks

What are "key clicks"? How much does the rise time or bandwidth of a CW signal need to be limited to prevent other QSOs on adjacent frequencies from being annoyed by "key clicks"? Is there a legal ...
5
votes
2answers
254 views

Share wide band antenna with multiple transceivers

I'm trying to incorporate several transceivers on my board design; I need WiFi (2.4 GHz) SatCom (~1.6 GHz) RF (~900 MHz) and GNSS (~1.5 GHz). I need to combine them into one antenna. I found a wide ...
5
votes
1answer
881 views

How do PTT buttons work?

I'm really new to this, and I was wondering how the whole PTT system works? I have a headset with microphone, and a Baofeng UV-82 radio. I know the radio has its own PTT button, but is there any kind ...
5
votes
3answers
369 views

Unlicensed TV broadcasting power limit (Band I)

I'm curious what is the legal limit for unlicensed TV signals being transmitted on the VHF Band I? This seems ill defined. The part 15 FM rules I am assuming don't apply here. And I don't think it ...
5
votes
2answers
799 views

How to transmit images and video through a hurricane?

Background You're in the path of a hurricane, and the eye just passed over your head. There is no electricity (apart from your own generator or battery), there is no mobile network and there is ...
5
votes
1answer
163 views

How to create a simple 1296MHz transmitter?

I have asked this quesion on other sites, but want to try to repeat it here. Also I have asked question about multiplier, and this is a different question. I discovered a 1296MHz beacon in my city ...
4
votes
2answers
93 views

Pi Matching circut for tube PA - what values?

I am working on my 80m and 40m CW transmitter and ran into a problem: I need to match the high impedance of PL504 to 50ohm coax, a Pi match seems to be the best, but I don't know how to calculate ...
4
votes
1answer
108 views

Will I get cleaner keying by keying the oscillator, or interrupting the amplifier B+?

One of my goals as a new ham is to homebrew my own transmitter (using vacuum tubes, aka valves). Initially I'll stick with CW for the transmitter, though over time I might build an AM modulator or ...
4
votes
2answers
157 views

Is using a DDS chip directly a viable way to transmit 2FSK and PSK on HF?

I'm thinking of building an HF transmitter for data (AX.25 or PSK31). Rather than using an IF stage, I'm thinking of generating the RF frequencies (or phases) directly with a Direct Digital Synthesis ...
3
votes
1answer
341 views

Detecting the listeners

I wonder, if a broadcasting radiostation can detect, how many receivers are tuned on it, and if it possible - how exactly this detection is happening? Thanks.
3
votes
2answers
166 views

Can I have a signal generator on while it's not connected?

The unit in question is an Elecraft XG3 test signal generator. It puts out anywhere from -107 dBm to 0 dBm. Is it safe to have these signal generators on and transmitting while not connected to ...
3
votes
1answer
567 views

Audio Morse Code to CW converter?

What kind of circuit can be constructed and/or could be used to convert audio containing Morse Code sounds (say from an old practice tape, or from computer generated audio) into key, switch or relay ...
3
votes
4answers
356 views

Low power long distance wireless data communication

I am looking for a communication solution with the following requirements: wireless unidirectional, point to point low power (li-ion battery powered, should operate at least one hour on the single ...
3
votes
3answers
792 views

What is the output impedance of a typical solid state ham transmitter?

I've often heard that the output impedance is 50Ω, and the load impedance should be matched to that and also 50Ω. While the reasons for the load impedance to be 50Ω are clear, is the output impedance ...
3
votes
1answer
267 views

SSB modulation image rejection

I'm trying to figure out how SSB transmitters manage to get rid of the images created when mixing up audio frequencies. For example, when mixing a 1KHz signal with a 7MHz one you will end up with two ...
3
votes
1answer
2k views

Jamming with USB SDR

Could an attacker use a simple USB SDR dongle, as long as it is capable of transmitting within a certain range, to jam frequencies? I saw Lady Ada build the WaveBubble which is basically a dual-band, ...
3
votes
4answers
143 views

How is working on DC high voltages as in a tube radio different from 120VAC?

Suppose that I am familiar with the safety procedures for working on 20 A 120 VAC 60 Hz household lines. What should I be prepared for before working on high voltage DC circuits (say, 800 volts) as ...
3
votes
0answers
75 views

Can anybody identify an appropriate radio for this game? [closed]

Complete radio ignoramous here. I've been playing a game called The Blackout Club, and I'd quite like to make a 3D model of a radio set for it. The game is set around 2007 and, as in the picture ...
2
votes
2answers
508 views

Is my low-power VHF transmitter dangerous?

I use a Raspberry Pi for transmitting FM on 107.9 Mhz. It uses square waves and has a power of approx 0.085 Watts, but just to be safe: If I have a 1 watt transmitter approximately 1 metre away from ...
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
104 views

Where does this common spurious transmission come from? Is there a quality difference?

I decided to see what my ham transmissions look like on an SDR and was kind of shocked to see how much leaks out. The waterfall display is split between two handhelds during transmit. There are a ...
2
votes
1answer
114 views

How does one know how a signal has been modulated

I am trying to intercept signals from a drone remote controller and decode them. Before I can do this I need to demodulate the signals. All I have is radio data from the transmitter's operating ...
2
votes
2answers
148 views

How does keying a CW transmitter work?

In my handbook it talks about keying the transmitter to produce the dots and dashes. Does this mean that the operator is turning the transmitter on and off, or does this mean that the key is turning ...
2
votes
2answers
998 views

What is a “dip relay” and how does one use it to build a transmitter?

Reading a discussion on low parts count transmitters, I came across this description, which lacked schematics and build instructions: Re: PROJECT 14: THE WORLD'S SMALLEST TRANSMITTER Are y'all ...
2
votes
2answers
109 views

What does radiation power mean?

I would like to ask you what it means when it is written that a transmitter has 10 dBm power. Does that mean that 10 dBm is provided to the antenna, or that 10 dBm is measured at particular frequency ...
2
votes
1answer
176 views

Is it possible to generate rf by directly programming a pc parallel port?

From what info I've found, it seems a pc parport has a max speed of ~2meg /sec ? So transmission on medium wave, to ~160 meters should be possible ? With antenna than possibly a small wire, I ...
2
votes
1answer
1k views

How to set trasmit freq. on Baofeng UV5R to 0MHz manually

On this quesiton: How can I avoid accidentally transmitting with a Baofeng UV-5R? I learned how one can avoid accidentally transmitting on a Baofeng UV5R. This can be done using software by setting ...
2
votes
0answers
407 views

LimeSDR Mini + Raspberry Pi 3 B+ Transmission problem

I am new at this. I would like to transmit an audio signal cleanly using WBFM but I see two signal peaks occur around my fundamental frequency when I start transmitting. In this case I am using a ...
1
vote
3answers
266 views

Weird Harmonic Issue on Raspberry PI FM Transmitter

So I talked to my neighbor about my Raspberry PI, harmonics and his emergency radio. He told me to fire it up, as we saw the FCC sticker on it, meaning it is in compliance with Part 15. I started my ...
1
vote
1answer
60 views

What happens when you directly couple the transmitter antenna to the receiver antenna?

I was wondering what happens when you directly electrically couple the transmitter antenna to the receiver antenna? Particularly I’d like to know what happens for FM radio broadcast. Since I don’t ...
1
vote
3answers
108 views

Is there a risk of interference between a 403 MHz and a 433 MHz Radio?

I hope the question is not too stupid, as I am very new to Radio. According to my logic, the obvious answer is no. However I believe to have read somewhere that interference may be a problem when the ...
1
vote
2answers
237 views

How difficult is it to build a basic transmitter and receiver

Preferably something that could transmit LED lights, like patterns. After that I'd like to advance to audio and video. But for the basic radio transmitting and receiving how difficult of a job would ...
1
vote
1answer
91 views

Is there any way in which elevation *does* affect medium frequency (AM radio) transmissions?

This is a followup to this question of mine. From reading the wiki article, I get that: Radio waves at MF wavelengths propagate via ground waves and reflection from the ionosphere ( called skywaves)...
1
vote
2answers
134 views

Reproduce ambient EM fields inside a Faraday cage?

I am part of a research team looking at the possible effects of EM fields on psychological function. The experiment calls for participants to perform a series of tests while inside a Faraday tent that ...
1
vote
1answer
113 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 ...
1
vote
1answer
46 views

What circuit to use to multiply 434 MHz by two?

I wanted to make an experimental simple 1296 MHz transmitter to have fun with my sdr dongle. But after hours of googling I realised that there is no such thing as "simple 1296 MHz transmitter". Even ...
1
vote
1answer
89 views

Why would a nearby antenna cause intermittent transmission?

I'm having an issue with some handheld transmitters, and not sure if they're bad, or the newly-installed antenna is bad, or if this even makes sense. I've been using a handheld Icom aviation radio (...
1
vote
1answer
62 views

did static fry my uv5r?

I was hit with a big arc of static from a metal door frame. I was a little over a foot away. It stung pretty good, then my coworker told me I was transmitting. My baofeng uv5r will not stop ...
1
vote
2answers
82 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 ...
1
vote
1answer
240 views

Would I be able to legally operate this FM transmitter without a license in Canada?

I've been looking into FM transmitters, and I've found one that I think I may use. The transmitter is based off of the KT0803L integrated circuit (http://radio-z.ucoz.lv/kt_0803/KT0803L_V1.3.pdf). The ...
1
vote
0answers
59 views

Parasitic inductance of relay contacts

I need to switch a bank of filters operating on bands from about 2MHz to 30MHz. The parasitic series inductance of the relay contact system will have an effect on the performance of my system. ...
1
vote
0answers
76 views

2GFSK 9600bps Transmitter and amplifier for 433 MHz

I'm looking for a reliable, however cheap solution for ground-space communication. I need at least 50W of transmitted power with 2GFSK modulation at 70cm band (433 MHz). Transmission will be done ...
1
vote
1answer
131 views

International Broadcast - database programs? [closed]

In my search to identify the stations I can (barely) hear on my small shortwave setup, I discovered the HFCC. They have a tool that takes your location and UTC time, and provides a list of stations ...
0
votes
1answer
95 views

How hard to send files [duplicate]

How hard and expensive would it be to send a file from my house in London to a coastal area in Spain? It would most likely be software I want, so it must transfer perfectly, however if it is feasible ...
0
votes
1answer
54 views

Can radio waves be made to travel as or along a particle beam? [closed]

Can a laser be used as an antenna? Can a beam of any type extend transmission distance of an electromagnetic field? https://medium.com/starts-with-a-bang/this-is-why-the-2018-nobel-prize-in-...
0
votes
1answer
831 views

Ettus B210 USRP Is it possible to transmit on both Tx Ports either with same or different application?

Just getting up to speed on the ettus B210 - basically the same as the B200 but with two Rf boards. I am testing using gnuradio-companion. I have setup a very simple transmitter consisting of: ...