What attracts a lot of people to amateur radio is that it gives you the ability to make your own gear. Scratch-building hams usually start by making their own antennas, but eventually, the itch to build one’s own radio must be scratched. And building this one-transistor transmitter is just about the simplest way to dive into the world of DIY radio.
Of course, limiting yourself to eight components in total entails making some sacrifices, and [Kostas (SV3ORA)]’s transmitter is clearly a study in compromise. For starters, it’s only a transmitter, so you’ll need to make other arrangements to have a meaningful conversation. You’ll also have to learn Morse code because the minimalist build only supports continuous-wave (CW) mode, although it can be modified for amplitude modulation (AM) voice work.
The circuit is flexible enough that almost any part can be substituted and the transmitter will still work. Most of the parts are junk-bin items, although the main transformer is something you’ll have to wind by hand. As described, the transformer not only provides feedback to the transistor oscillator, but also has a winding that powers an incandescent pilot lamp, and provides taps for attaching antennas of different impedances — no external tuner needed. [SV3ORA] provides detailed transformer-winding instructions and shows the final build, which looks very professional and tidy. The video below shows the rig in action with a separate receiver providing sidetone; there’s also the option of using one of the WebSDR receivers sprinkled around the globe to verify you’re getting out.
This little transmitter looks like a ton of fun to build, and we may just try it for our $50 Ham series if we can find all the parts. Honestly, the hardest to come by might be the variable capacitor, but there are ways around that too.
[via SWLing.com]
Here’s my reply from elsewhere when somebody else thought this was a good idea to repost.
We really need to end this fixation on extreme simplicity.
Everyone should build a crystal oscillator, that was the first radio thing I built that worked. But you don’t need power, it’s something to hear in your receiver.
Yes, some like to build simple for the challenge, but they generally know how things work. Beginners need to start simple, but those don’t make the best rigs, and nowadays low power, CW and crystal controlled will present obstacles. It was intimidating the first time I operated with my license, and I was using someone’s Collins KWM-2.
And simple is never enough, someone recently showing a circuit that “had no hard to make coil”. But that caused impure output, something a beginner might not know. Winding a coil is part of building a simple transmitter, learn the basics and advance.
There is no way that someone would have an RF capable power transistor, but not have a bunch of low power transistors. Adding a separate oscillator before the power stage adds
virtually nothing to complexity, but gets rid of some of the problems.
In an emergency, a crystal will be the biggest problem, not parts to build a two transistor transmitter. You won’t scrounge a ham band crystal (unless there’s an analog tv set to offer a 3.58MHz color subcarrier crystal), and out of band means it had better be a real emergency. An odd frequency reduces who is listening, and CW eliminates most people from understanding what’s sent. Do the Boy Scouts even bother with morse nowadays?
Ham radio has focused too much on “emergency communication” rather than technical. This seems to represent that. Simple rather than good. There seems to be a lot of hams who never go beyond simple, finding some excuse. So people are stuck in 1971, which is just a solid state version of the 1920s. And synthesizers and frequency counters and receivers with higher IFs existed that year I found the hobby electronic and ham magazines.
Ham emergency communication is about providing communication to third parties, not being stuck somewhere and having to build a transmitter. Carl and Jerry in their fictional emergencies at least built spark gap transmitters from cars and tv sets.
After 30 odd years as ham operator I would have to agree the idea of Ham radio for “emergency use” is somewhat more idealistic than reality for at least most of the world. Thats not to say it is never used for that purpose just highly unlikely
But a simplistic transmitter can be a great project and some operators do get a kick out of operating a such a rig. It certainly has a lot more appeal to me than a station running multiple KW with an antenna bigger than a small European country.
This project was presented as an “emergency transmitter” when it was posted at the swling.com blog.
In the 1930s lots of people got into radio with one tube radios and one tube transmitters. You could do better, but not by much. Parts were expensive and bulky, and it was the depression. People didn’t do hobby electronics, they did hobby radio. A first project wasn’t an electronic organ with tin can keys, it was that receiver and transmitter.
Even fifty years ago a one tube transmitter maybe made sense. It was kids getting into the hobby, and they had little money. Transistors were still a relatively knew thing. The US Novice license created a space for beginners, all using low power, crystal control, and CW. Surrounded by people like you, everyone was the same.So
A lot of those transmitters weren’t built through understanding, they were exactly copying what was in the article.
And many went nowhere further, once they upgraded their license, it was commercial equipment. They saw that single tube transmitter as obligation, rather than a first step to technical mastery.
So there’s mythology about those ancient times, and not much thought about it, just acceptance.
When the hobby pulls people off the street now, it’s not for the technical aspects. They also aren’t kids. They skip all that, go directly to commercial equipment. They expect variable frequency, and using the same frequency for both ways. They may not know the code. They’ve got money.
But here and now, people aren’t all beginners. They may not know radio, but they are interested in technical matters. They’ve probably built more complicated than this transmitter. They are older and have money, or a junkbox of parts. They may be put off by the “mystique” of radio, but not by complicated projects (unless I’m misinterpreting the readership here).
When I was 12 and on the verge of getting my license, I wanted to build a 50 MHz DSB suppressed carrier transmitter. Skip that CW stuff, go to voice, but be “modern”, no carrier (so most would think I was SSB) but simpler to build than SSB. Likely crystal control, but that was still more common. But money got in the way. I did build an SSB transmitter a few years later.
We mustn’t scare people away, so we trot out these same simple transmitters as decades ago. No growth. Parts are cheap and small, but foist a single transistor transmitter on the beginner, with all the faults and limitations.
Build that single transistor crystal oscillator, then build it again as the first stage of a better transmitter. Look further than simple, to see that adding parts makes things simpler. Add a few more parts and you can have voice, compatible with way more people. Understand beyond your means, so you may not build that complicated receiver, but know how it works, appreciate the design.
Have you stopped to consider that the kids today are starting at the same level of knowledge and experience that the kids of 80 years ago did? I know it’s hard to believe, and it seems to work the same with learning to talk. Every dang one of them starts off with “maaa”. Can’t we evolve past this?
Kids don’t come into the hobby. And I gather most who come to the hobby aren’t building. In Canada you can’t build your own transmitter with the entry level license, in the US entry level meant VHF until recent changes.
But we’re stuck with the mythology of the past.
Right at this website, where people like to present themselves as “hackers”, isn’t it more likely that people are more capable, that this won’t be their first project? If they are lured by the technical, then the technical is the appeal?
So they are foisted with an extremely simple transmitter that has limitations, and requires learning code.
I don’t like the idea of a power oscillator, but that made me question what’s going on here.
If this had been a two transistor transmitter, I likely wouldn’t have said a thing. A separate oscillator would add nothing to the cost, and little to the complexity, but it moves away from novel.
If you’re starting with the assumption that no children are getting into the hobby, that a) explains your position on simple transmitters and receivers, and b) is an admission that the hobby only lasts until your generation dies out. I see that we’ve been operating on totally different assumptions, and if yours are right, then there’s no point in even discussing it.
Actually an answer to Michael Black…
Somebody forgot to tell the people at New England Amateur Radio that kids aren’t coming into ham radio.
https://www.facebook.com/NE1AR
https://www.ne1ar.org/
New hams aren’t mostly young like they were back in the day. But young people are still becoming hams; we should welcome them and make sure to offer activities that interest them. Some of them even like Morse Code; secret codes have long had an appeal to children.
The threat of rogue nations now just nearing the ability to create nuclear weapons and the probability of those weapons being triggered in the atmosphere over the USA is greater today than ever. Having the ability to create a simple transmitter and a simple receiver along with knowing morse code will be the only method other than smoke signals and flashing light of communicating after such a terrible thing has occurred. Just something to keep in your thought lockers as we enter into a new administration that is friendly with Iran and willl give more of OUR tax dollars to them … because after they make good on their attack on Israel, they’re coming after us. The old Boy Scout axiom is a good idea even today… “Be Prepared”
You should do something with that crystal superiority complex of yours. For decades people built radios, both transmitters and receivers using only LC tank circuits and no one had problems with that. Many common low power small signal transistors can work up to 100-300MHz, while power transistors capable of that are rarer and more expensive. And this simple 1-transistor transmitter is just an oscillator, which, accidentally, is also a building block of more complex radios…
It’s a keyed oscillator, so crystal control is important for frequency stability. A high power keyed oscillator without a crystal would be nearly certain to have unacceptable chirps or yoops. It might be possible to tame it with very tight voltage regulation, but now you’re moving out of the realm of simple circuits.
Well duh! You just make it a non-keyed local oscillator, you take signal from the third winding to PA via single transistor AM modulator or cascode, or dual gate MOSFET, which is a cascode in small package…
You could probably get away with connecting the output of oscillator to PA via a capacitor and shorting the PA input to ground with a normally-closed key or transistor…
Then build a crystal oscillator, throw it away, and build a multistage transmitter. Like I said, there’s very little difference between this and a two stage transistor transmitter, and we had those in 1971 (I checked, there’s one in the 1971 ARRL Handbook).
You don’t need power if you’re adding an amplifier stage, but you’ll be stuck with the problems of a power oscillator.
And making a good variable oscillator at 7MHz is harder than building a two transistor transmitter, not because “rf is hard” but because stability is hard. There have been rules in place since the thirties that a ham transmitter have the stability of a crystal. So that’s the goal.
And the simple LC tank uses that “hard to make” coil. While I do not know what should be hard on winding a few meters of wire, if necessary on an empty toilet paper roll, if I really have to go simplistic.
Gotta disagree, here. I will concede that a one-transistor (or one-tube in ancient times) transmitter isn’t very useful without a receiver, and a one-transistor receiver is going to be pretty close to useless, I think it’s of great value to have conceptually simple radios to build, even if you can only contact your friend three blocks away. Sure, a double-conversion multiband superhet transceiver with digital signal processing is a great thing to have, but what do you learn about electronics by buying one? When I was a kid around ten years old, I wanted to build a radio. Nothing tricky, just an AM superhet, since I had already done the basic tuner-detector-audio amp radio. I even found articles in various library books that covered all of the modules – local oscillator, mixer, IF amplifier, detector, audio amplifier. I didn’t end up building it, because there were too many parts that I couldn’t find and didn’t know enough about to make sensible substitutions (things like IF transformers and mixer transformers specified with Miller part numbers), but the point was, each module was simple enough to build and test on its own. A little later I did have a shortwave radio (Heathkit GR-64), and I built a BFO accessory for it, even though the GR-64 had its own BFO, just to understand how that worked. There were also lots of articles that gave complete plans for things like signal injectors for RF and IF frequencies, for testing and troubleshooting radio receivers. Simple things that had practical applications.
While simple radios may seem to be useless today, with everybody wanting to do digital modes and other modern things, this doesn’t mean you can just skip over the basics, because the complicated things are based on the basics. You are right – emergency communications doesn’t mean building a transmitter when the emergency need comes up. But it DOES include having the knowledge to be able to make a radio work when it has crapped out and you need one in an emergency.
I have no experience with one-transistor receivers (yet), but very simple one-tube regenerative receiver is more than capable of receiving transmissions from all around the world in AM, CW and SSB modulation.
The cheap 433 MHz radio controlled switches/sockets had a one transistor regenerative receiver for years. Now they slowly become crystal controlled and that is a great advantage, because the regenerative receiver produces interference and disturbes other nearby receivers.
Of course, in an emergency this would be of low priority and luckily you would not need to use a tube for this principle.
Dude, you’re taking it much too seriously. Also, a new diy’ing ham has to start somewhere. Simole projects are a good start. Pointless to immediately jump into a bitx.
There are ways around the need to wind coils. Radios can use manufactured inductors, or the designer can put inductors on the PCB itself as some designs from 4SQRP have done. One example of that: http://www.4sqrp.com/cricket40.php
Back in the day there were commercial inductors, like 7×7 ones, that were used in both radios and TV sets. They came in variety ot types and values, all had a ferrite slug for tuning and were very common. Nowadays almost no one uses them…
In many cases the slugs were used because the circuits were narrowband and the tuning slugs put the peak in the right place. It was common on household radio receivers for the IF selectivity to come from an LC filter using those slugs. That’s why IF filters are designed for specific IF frequencies: they have the right amount of inductance to resonate at that frequency, and sometimes even have the necessary capacitor built in.
Nowadays we usually design broadband stages (easier to do with solid state than with tubes) and get the selectivity from crystal or ceramic filters or DSP. One reason is that manufacturers don’t want to make radios where each one requires manual adjustment before shipping; they want things that can be built by robots.
Alas, it makes it hard to build some of the vintage ham designs from the 70s and 80s. We either have to find NOS parts, change the design for different components, or abandon the idea altogether and build a more modern rig.
Air variable capacitors are getting scarce for a related reason. Nowadays new designs use frequency synthesizers, so there is no need for a capacitor-tuned VFO and therefore no need for those capacitors. Varactor diodes (diodes with capacitance that can be controlled by changing the bias voltage on the diode; they were used as substitutes for air variables in a lot of radios and TV from the 70s and 80s) are disappearing for the same reason.
And finally, we have the big disappearance of ICs and passive components designed for through-hole mounting. Nearly all modern electronics use surface mount parts and so that’s what the component manufacturers make. That also leads to some seemingly odd parts like the “through hole” MLCC capacitors that are really an SMD part with wires soldered to the ends and an epoxy blob around the SMD cap.
But for high frequencies SMD is really the way you want to go. Much less parasitics.
Zener diodes capacitance is voltage dependent, so it could be use as a Varactor for a narrow range.
They are of couse not optimized as such.
I found some coils with a few windings and a tuning slug on Aliexpress a few months ago for cheap. So you still can buy it. But where is the problem to wind a small coil? We are not speaking of 100ds of windings.
I have sat down and wound a couple of Tesla coils (~600-700 turns) with 32AWG while watching TV. What’s the big deal anyway with posers that can’t do any manual work these days?
I wouldn’t call it inability not to do work, but to learn skills. Like soldering, for example. You want a string of multicolor LEDs in your project? Buy them and plug them into an Arduinoclone. Have you SEEN the ecosystem for Arduino variants these days? You buy sensors that are on breakout boards that have specialized I2C jacks on them (not just pin headers, but polarized connectors) so you can daisy chain any number of devices together. And you can buy the jumper cables to plug these into the Arduinoclone. Things just work, as long as they can be made as simple as plugging in a toaster, and as long as there’s a pre-written library for each pre-made device. So, wind a coil? I have to count the number of turns, of a specific diameter and length? Hey, I’ve got a better idea: I can make a radio out of my phone, by going to websdr.org. It’s kind of hard, though, because the frequency channel numbers are like five digits long.
Exactly! Many first coils are wound round a cardboard toilet-paper tube. There’s no app for that 😁
Traditionally, coils were a problem because most hobbyists didn’t have a good way to measure the inductance of a coil. So if you had some coils with ferrite tuning slugs salvaged from mystery electronics, you a) didn’t have a clue what the inductance was, and b) didn’t know how many turns should work out to what inductance because you didn’t know enough about that ferrite slug. Today, we have cheap Arduino-based “component testers” that will just flat out tell you what the inductance is. And by the time you get to experimenting with circuits where things like input and output impedances are important, we even have vector network analyzers available in the hobbyist price range.
But come on, now. Is it that much of a barrier, given instructions showing the dimensions of an air-core inductor form and the number of turns, that you don’t want to wind that coil yourself? I’m having trouble understanding the reluctance. No pun intended.
There also were spider web coils (or honeycomb coils ?)
– Many OMs/SWLs seem to forget this fact.
https://www.instructables.com/Spider-Web-Coil/
Making them isn’t hard, just needs a bit of patience.
Even I managed to build them. 😁
And last, but not least, these coils have an esthetic value.
But what am I saying, the kind of operators who like the 817 perhaps have no interest in such things, hi. 😂
My point about coils was that someone who wants to be a leader, maybe even a teacher, is catering to people’s perception of coils, “they are hard”, rather than addressing the issue so as to make coils “simple”.
The Maker Movement is about dumbing down. People want the results rather than the path getting there. So we have statements like “wiring an LED is the equivalent of ‘hello world'” but then insisting that there should be LED modules so beginners don’t have to solder.
But wiring an LED is about taking that first step, which includes soldering.
Once you’ve decided the only way to get beginners is through a one transistor transmitter, then you end up trying to make it even simpler because a coil will keep people out.
The guy who gave that line about “coils too hard” is stuck with coils because he’s still building from 1971 or 1921, and coils had a much bigger place in radio back then. Now, coils are only used because they are necessary.
Well, so be it. RF IS hard. If coils scare you off, we might as well just get that out of the way. I agree with your assessment of things being overly dumbed down. Einstein said something like “Explanations should be as simple as possible, but not simpler.” (I hope I didn’t oversimplify that.) The thing about RF is that by its nature you can’t see it, and you can’t observe it in real time (although sampling scopes kind of cheat their way around this). So it’s one step harder than baseband electronics. You deal with it, or you just don’t.
But this is why I think that simple projects are a good way to get over that initial barrier. Once you get the idea of what it takes to tell what’s going on in an RF circuit, and what construction methods just won’t work, you’re over that first barrier. But it doesn’t stop getting harder, and that’s part of the attraction: you work at learning harder concepts and more effective techniques, because they get you better results, and you join a class of wizards.
But you really can’t avoid coils, because even a straight piece of wire has inductance, and what we really mean here is inductance, not coils per se.
But this was presented as a transmitter to go on the air. So you get one that will have issues, and will be limiting, just so it can be simple.
The values will change, but the exact same circuit could be a low power oscillator. Learning wise, it’s the same thing. All of this assumes a receiver (else you wouldn’t need a transmitter) so you can receive the oscillator. Unplug the crystal, the signal goes away.
Or, pull a uA tuning meter out of a junked stereo receiver, with a few other components, and you have an uncalibrated RF meter. Unplug the crystal, the meter will drop. You will know it’s oscillating, but with no receiver, won’t know the frequency.
Want to modulate it? There are various ways, for the purpose of experimenting. Apply an audio signal one place, you’d get FM, except them crystal will limit deviation. Another place, and you’ll get AM. Add a couple of transistors the right way, you get DSB suppressed carrier. Just like SSB but two sidebands.
Then add a stage of amplification, you get your transmitter to put on the air, and already know more than just building this transmitter.
Or start with an LC oscillator, no crystal needed. It will give insight into drift.
At the frequencies of this transmitter, RF isn’t hard. Different isn’t the same as hard.Keep leads short, build on blank circuit board for a good ground return. An RF oscillator is no harder than an audio oscillator. You can build a low power one for experimenting without even winding a coil.
RF is a mystery because people say that, and it’s new until it isn’t.
Why should the first step be a transmitter rather than an oscillator?
If you’re interested in electronics, you want to learn, and that first transmitter isn’t an obstacle to overcome.
All of this happened to me when I was 12 and 13.
I DON’T think a transmitter should be the first thing. Especially if you have no way of measuring harmonic content. I completely agree that an oscillator should be first, and ways of measuring what that oscillator is doing is the next priority. An RF voltmeter, in the form of a detector and a meter, is good, and a way of measuring the frequency, whether it’s a frequency counter or just a receiver with a trustworthy dial. There are Arduino-based frequency counters out there, both as drawings and as full kits with pre-programmed microcontrollers, so you don’t even have to have the ability to program an Arduino. In HF, all but the lowest range of oscilloscopes is adequate to see if your waveform is relatively clean, and get a rough measurement of the frequency, so that’s an option as well.
But it IS okay to follow someone else’s instructions for a basic transmitter, which in this case is just an oscillator anyway. You just need to have a pretty accurate way of measuring its frequency before connecting an antenna. This is what many hams have done over the decades. Not having adequate ways of measuring your transmitter is not an excuse for splattering the bands with crap, and we have license tests to ensure that you are aware of that.
Very nice work. It is especially good that harmonics are very low, even without low pass filtering.
Pretty design too.
I’ve always figured that if something can be built… well… we can build that something too. Also, using whatever materials are available… albeit not typically with ideal performance characteristics. Like in machine tool in high school, we first learned to use a scribe, rule & other gauges/tools, ink, hack saw, file and drill. Technically, a hand drill can be used… like the old fashioned ones.
Get’s me thinking regarding the variable capacitor, making a range of the various improvised and DIY designs and then tabulating the performance characteristics to observe how they all perform uniquely.
Wondering how the maker space or fab labs CNC mill or laser printers can make mundane repetitive work significantly faster in regards to making a nicer plate variable capacitor?
Might even be worthwhile to hire out to a shop if cutting enough parts.
A simple Google images search of “PCB variable capacitor” is inspirational for the homebrew ways… minus the tin foil ones and not seeing the trombone or pipe variants. For those, just replace “PCB” in the search term with “pipe” or “foil” or “trombone.”
Used to be, every junk radio out there had a two-gang variable capacitor in it, and those were fundamental in building things that needed to be manually tuned. But today, most oscillators in consumer electronics are synthesized, varactor-tuned, or both, making it hard to find variable caps. But hey! Turns out you can make your own, and tailor them not only to the capacitance range you want, but also the profile, i.e., the transfer function from dial position to frequency, for example. Good times!
It’s actually easy to use a reverse biased run-of-the-mill diode like a 1N4148 or the PN junction of a low signal bipolar transistor as a varactor. You won’t get as much of a capacitance range, but you can parallel a few to get a reasonable amount of tuning for an oscillator.
Not sure if I’m off base here (Hurr hurr, sorry) but I am thinking that the crappier the transistor, in RF performance, the more capacitance the emitter base junction has???
LEDs are better as varactors.
i) do you have to keep them dark? reverse biased ones are meant to work as weak photodetectors or cells. ii) is it the bigger voltage drop the better, because some green ones are near 4V ?
And then you get AC hum when the LED gets modulated by the table light over the workbench.
This really happened, except the guy was using small signal diides, with clear glass casing.
Black heat shink tubings on parts should help. You can crimp them shut while they are hot and sticky.
Yes, every semiconductor junction is a varactor. If you shop for diodes or transistors with large die sizes (i.e., large average current specs) and low reverse voltages (thinner junction), you get high junction capacitance and therefore a larger variation in capacitance. You do have to shop for it since this is not considered a selling point, and not every datasheet shows capacitance vs. reverse voltage across its junctions. And you can get varactors this way that are very cheap, but you have to be careful because if the particular part you specify goes out of production because it has been replaced with “better” (i.e., lower capacitance) devices, you have to go shopping again.
The larger problem is that to control that capacitance and therefore get the repeatability and stability you want for your oscillator or filter, you need to control your power supply to it very well. Phase-locked and frequency-locked loops use feedback to stabilize them, but this comes at a cost in phase noise. Every cheap solution produces its own new problems.
So that might be a way of sniffing out fake parts. The 2n3055 for example, the die is massive, you could get several ARM cores on it these days, the fakes, when you decap them, have a tiny scrap, made on a far more recent process. But you don’t have the sheer bulk which translates to power handling. Soooo, the fakes should have a lower junction capacitance, and they should have a higher oscillation frequency. So then you’ve got something to weed them out with, without decapping everything, or seeing if it explodes with more than a handful of amps through it.
Also zener diodes – larger selections based on rated voltages.
Hellschreiber (Feldhell version) also uses CW – Continues Waves (undamped waves, on-off keying).. ;)
https://hackaday.com/2015/12/30/messages-from-hell-human-signal-processing/
https://hackaday.com/tag/hellschreiber/
Bet it chirps like a songbird!
There are good reasons why the MOPA design is not more widespread.
Watch the video. It chirps veeery slightly. Perfectly fine for a little fun project.
this working on ism band and can send digital signal?
we have 21 milenium
Nice work!
I think we need to push these simple cw transmitter projects more. But not just that…
Ham radio is a multi-faceted hobby. There are contesters, emergency preppers, ragchwers and more who can easily start out on voice modes and be happy. But when your interest building and the technical side of things it isn’t so easy. Voice transmitters are hard, receivers even harder. I’m not saying it isn’t possible but most people don’t do very well if that is their first RF project. It’s discouraging.
And don’t get me wrong. I know there are a lot of people out there who really enjoy their Morse code. More power to them! Perhaps many people who enter the hobby in other ways could eventually catch that bug and learn to enjoy it to. But I just don’t see a large number of today’s internet enabled hackers and makers going through all the effort of becoming proficient in Morse code just to gain access.
But it’s CW transmitters that are the easiest starting point. That’s kind of a dilemma which I think holds the technical side of the hobby back.
A few years back I decided to give computer generated Morse a try. I connected my little 5W QRP transciever that my wife bought me in the hopes I would some day be good enough at Morse to my computer. I found that software is just fine for sending Morse but it’s only really good at receiving it from other computers. You have to figure out the speed at which the other person is sending and tell the software so it can decode it. Real people just aren’t that consistent in their speed and software isn’t as good at following the constant variation as a human brain.
But I did find myself on the Reverse Beacon Network http://www.reversebeacon.net/. My little signal from Ohio was picked up in Oklahoma! I think that proves those people that say “Life is to short for QRP(low power)” are full of crap.
So, anyway. What I think we need are more people sending and receiving CW via computer control. That way when someone wants to build a transmitter but isn’t ready to learn Morse there is someone they can actually talk to. But I can see this really getting on the nerves of “real” cw fans who already complain about all the “no code extras”. That’s ok though because we still talking about low power simple devices. Even with more people out there doing it we would want to cluster around just a couple of frequencies in order to increase our chances of actually finding one another and having someone to “talk” to. We wouldn’t be taking over whole bands with computer generated morse!
I’m imagining some frequency where one can go and find a bunch of new hams from this community using FLDigi with their simple homebrew rigs to talk about the latest HaD article or 3d printing, arguing Arduino vs Pi vs 555 or something like that.
But like I said. It’s been a few years since I tried this. Maybe today the bands are already full of people transmitting computer generated morse and all I need to do is hook my equipment up again. I don’t know.
If anyone wants to try, you will need a little more circuitry to do this. Most software just outputs to the soundcard and you need a circuit that detects that and uses it to key your transmitter. If you have a serial port you might find a simpler method using it’s control lines but unless you are using an RTOS that might not always work. Here you go. http://www.w1hkj.com/FldigiHelp-3.22/cw_keying_page.html
Then again, as long as we are talking about really low power coming from single transistor devices maybe one of the ISM bands is the better place for this. No license required.
Since it’s CW, why not just get the license? With CW, you only need a Tech class to transmit CW on 80, 40, 15, and 10 meter bands. ‘Course, any day now they’re going to start charging a fee for license applications.
That’s very true and I didn’t mean to discourage anyone from doing so.
One thing I didn’t mention that I have thought for a while. It would be nice if a radio shack became a common part of a typical hacker/makerspace. (the older meaning, a place for playing with radios, not the store).
One argument against would be the liability if unlicensed people start messing around on the ham bands. CB would be safe but not too applicable since the only part you can legally hack on is the antenna. I’d avoid creating a Medfer station too since that’s shared with the AM broadcast band but hackerspace Lowfer and Hifer stations could be interesting. And of course receive could be wideband.
That depends of which country someone lives in, I suppose. In my country, someone is not supposed to modify the internals of a CB-Radio, but can build own external accessories just fine. Speakers, reception amps, modems, amplifier mikes etc. Also, using computer modes is fine, too. SSTV, Packet-Radio, APRS.. There are even special channels reserved for these. So essentially the CB operators are on eye-level with hams, when it comes to hams.
By the way, let’s never underestimate SWLs, also. I often hear that he/she is “just an SWL”. Some SWLs have in fact, better manners and operating techniques than the average OM. Due to their activities, they learn to be patient. Also, some SWLs are hams, too, but have a “call sign” that covers reception only. These folks did a perform a test, even with CW sometimes, to get their call. However, it does not allow transmission. These hams are listeners only, but participate on contests, too.
That call allows them to get/send QSL cards via the official channels. :) vy73/55
If we’re being pedantic — In the US at least, ISM band intentional radiators must be type certified. The only legal way for a hobby build your own radio transmitter to be legal is in the ham bands.
About computer-generated Morse, it seems like across all the CW neighborhoods in HF, 80% of what I hear is either 50, with about an equal mix of the two.
Oops – unintended WordPress consequences. I meant to say, “is either less than 15 words/minute or more than 50”.
BrightBlueJim,
A WAG there? I do quite a bit of CW. 15 wpm or less maybe at the top of the CW portion of the band and mostly with the SKCC group, below that 20 wpm and a little under. Contests? Sure. 30-40 wpm. 40-50 wpm would be an extreme rarity outside of a contesy
Not wild, but certainly casual – I don’t transmit CW at all, and only listen for practice. I wouldn’t call it extremely rare to hear over-40, as I stumble across it while looking for 20 WPM stuff. Not an everyday thing, but not what I would call rare. As a wild guess I’d say that the high speed stuff is usually at the low end of the 40/80m CW neighborhoods. Exchanges too long for contesting, so I’m guessing they’re just using it as if it were RTTY.
Hmm, these days there are chips that are so small but do so much in RF, although I think it’s a nice exploration to find some technical asymptote and in so doing can be a cathartic exercise for the few and even fun for some, it is unlikely to be as effective as a piece of crafted silicon. Although on 2nd thought, as I wrote the last line, one could couple a single transistor to one of those 1 cent chips to provide precompensation or whatever equivalent or some semi intelligent other functions for the cost of a smelly rag ;-)
Ironic that a chip similar in size to a two decade old conventional RF transistor in a package comparable to a plastic 2N2222 or equivalent can have comparatively more complex RF compensations, efficiency and reliability – car keyfob remotes one example.
There’s a Taiwan co Hope RF which if i recall from couple of years ago integrates a CPU with an output RF stage/transmitter for the short range approx UHF 433MHz keyfob band.
Nonetheless, thanks for post :-)
Cheers
I just saw this post after quite a few months where I was unaware it was posted. So let me make some things clear here, because I see a lot of confusion.
1. The goal was to build a transmitter with as low parts count as possible, but still be stable enough, powerful enough and usable enough. If you compare this transmitter to modern synthesized multi-stage transmitters then you’ve completely lost the project point.
2. Despite the few parts count, this is not a beginner’s project. A kid can’t probably build it without an experienced RF electronics man around. Also, there are high RF voltages involved. Also, this is not a simple to build project, it requires skills and care to be built correctly. Despite not a beginner’s project, if you build it like presented, it will always work at first power up.
3. If you have not tried it before, believe it or not, extreme minimalism is amazingly difficult to achieve. But that’s the challenge here, to try to do more or less the same thing with less components. Sure you can build whatever you want, 10 stages, complex circuits. Try to do more or less the same thing with 1 stage and then come and tell me how much time you will spend on it, if you succeed at all.
4. When writing a comment, at least respect the endless hours spent by the authors of experimenting and documenting and sharing the projects without any reward expected. It is quick and easy to dislike, or find all shorts of excuses not to build something, but it is way more difficult to GET YOUR HEAD DOWN TO WORK and design and perfect a minimalist circuit that works well.
5. READ CAREFULLY the page that describes the circuit. I bet some have just looked at the title and the photos and then started to comment. If you don’t read it carefully, your comments will be faulty and pointless. Because if you read the text, you will see the why’s and how’s behind this transmitter.
6. Even after all of the above, you still find this project pointless, I have news for you. Pointless things are part of what we call a HOBBY! Else it would be called a job. Personally I find these 10mW oscillators a bit pointless for real work on the air, but I would look with great interest a 10W transmitter if it was made with just a few components. But that’s what I think. What is pointless for you, may be a great find for others, so stop complaining and get to work!
Inspiring people, and especially younger ones, to look back and learn the origins of the radio electronic circuits, is a great goal, achieved in a great extent with simple to follow circuits. Such circuits give feed for more thought and discussion with elders. After all, building a simple project that works out of junkbox parts, is part of the fun of this hobby.
I do not think I will have the time to respond to more comments. Thank you all for your interest in this one.
Thanks for clearing the air of both QRM and QRN. As stated building a LP RF oscillator with good purity is a challenge… building a stable LP RF oscillator is a challenge…raising the power of such an oscillator, while retaining those qualities in a single stage is an achievement demonstrating considerable circuit design knowledge.
ON TEST EQUIPMENT FOR RF
If one is bitten and becomes serious to learn RF design skills feedback of efforts expended is near impossible without the ability to make measurements. The oscilloscope of course, but falls short as it works in the time domain. To measure R’s, L’s and C’s the window of choice is the frequency domain and the tool is the VNA or vector network analyzer. These used to cost in the 10’s of thousands today they start under $75, the price of a DVM, the NanoVNA’s are an example.
The final manifestation didn’t happen right off but is the result of hours of effort, some success many failures and rework. That is the journey of circuit design from DC to light. His final implementation is a fabrication masterpiece, techno art at its best. He’s a doer.
Not that I have an opinion…
I build rigs like this. It is fun, accessible and provides the option to improve and complexify. Many naysayers poopoo the idea of using such a rig. I know it isn’t for everybody but rigs like this can definitely get QSO’s and provide heaps of challenging fun a nd enjoyment. de VK2AOE
https://youtu.be/u35mrvdEpIo
https://youtu.be/CPmKFJGvc8w
https://youtu.be/lKgeB-b_tM4
Spark gap transmitters are even simpler and in an emergency situation would probably be the simplest to build. Real cave man stuff. I’m sure the FCC would be interested.