I´ve been following your channel for quite some time now, and I really appreciate it that you differ a lot from many of the hams out there. Hams on youtube mostly have one topic... It´s either Transceivers (+ them making a video about DX contacts) or Antennas... You make amateur Radio interesting to a wider audience by not showing these contacts (you do aswell, I know that) but also showing practical... beginner friendly... circuits that people can rebuild and will be able to get satisfying results... even with simple circuits. You´re lucky to have your amateur radio rules, because here in Germany (to my and my friends knowledge) AM is not allowed on 160,80,40... it is only allowed (HF wise) on 10meters... same goes for FM, and that makes a lot of easy do able experiments basically impossible... what does keep me and some friends away from the ham radio licence "do it for ... what?" (Also it´s very pricy here). Anyhow... about your circuit. The "motor boating" has nothing to do with the 10nF capacitor "long wire". It might give you a few nH, which are basically like "non existent" on these low frequencies. Your motor boating comes from RF "sneaking back" into your 1 transistor microphone amp, which then demodulates it, and modulates the transmitter with it... it starts to oscillate, and the sound you showed is the result. Add a 10...100nF Capacitor from base to ground (audio amp transistor) and there shouldn´t be any motorboating even with bad ground connection. I doubt it´s RF wise motorboating because you just have 1 stage after the oscillator. Also adding a 100nF in parallel to the 33R resistor can indeed improve the transmitter´s output power. Like you said, matching is important, but the problem with MF Frequencies is the hughe "inductive" current you get in the PI filter´s loading coil. Am into transmitter design 2 decades long, and building a 1W+ AM transmitter is an easy thing for me, but when matching the antenna... I realized that the loading coil eats a lot of power. At 1W, the inductors you use would "overheat and short internally" (Even far taller and far more expensive fixed RF chokes do get hot enough that you can´t touch em anymore and that just at 1W Tx power)... I use air wound coils with rather thick wire, that fixes it. The range depends on the antenna and grounding, like you hinted it. I used a 20 meters Antenna in one test, with a 2W (non modulated, PeP was higher) homemade transmitter on about 1250KHz. Ground is "Water pipe" from room heater. I didn´t make a full range test, but with a simple radio (not really a good receiver, but also not a poor receiver - it´s weakness is the small ferrite antenna as the whole receiver is tiny) I could pick up the signal a good kilometer "listen able" (understand what is being said without having to concentrate at the information). Anyhow... keep up the good work. I don´t know many "ham" youtubers that do stuff like you... on one side show ham radio realted stuff, but then show "DIY" electronics good for newbies. My friend also had rebuilt your ssb transceiver... but due to strict laws in Germany, he can´t use it even if he had the amateur radio licence (to low sideband supression -40 or -60 dB (super high) vs -15dB in other countries).
Very nice to see how you can make something good with simple things, I hope he will soon also make the hf stage really AM modulation! Healthy and Friendly Greetings from the Netherlands! Rob
Another really interesting video on the subject of AM transmitters Peter. I have put a couple of my failed experimental transmitters on the shelf due to this motorboating feedback problem which has crept in. My first transmitter would work well then suddenly burst into oscillation, a real pain which got the better of me. Interesting to see how you cured your problem. I like the idea of a crystal controlled transmitter as most AM nets have a fixed frequency. I am following your AM experiments with great interest...David M0DAD
Great selection of videos. I am currently making one if these basic transmitters. Building it on veroboard, strip board. Going to insert a small audio transformer in place of the 33ohm resistor. Also going to use a 386 audio chip for am modulation. Keep up the good work. Ps I may do a video if it works. Cheers from old George
I would suggest starting any transmitter project in a metal box with an antenna socket, even if you use this method of construction, housing it in a shielded enclosure will yield better results. A biscuit tin has depth and plenty of room. 73 de UK M0.
Altough it would produce AM (technically) it won´t work because the Base-Emitter capacitance (+ others) will generate a feedback to the oscillator and still cause parasitic FM. It would give better AM than the current circuit, but I highly doubt it would be useable practifcally. You´d still have to tune the radio to the side of the main frequency. You´d need to add at least one buffer stage between oscillator and your final amp (if you want to keep that simple oscillator circuit in your project) to prevent the parasitic FM from occouring.
After I posted that, thought it may be better in the emitter. Yes agree with the buffering to reduce FMing. A small handful of parts could make a almost usable AM tx. A quick check on a SDR or analyser could show whether it's effective.
After I posted that, thought it may be better in the emitter. Yes agree with the buffering to reduce FMing. A small handful of parts could make a almost usable AM tx. A quick check on a SDR or analyser could show whether it's effective.
I made the circuit from part 1, but got a real lot of Frequency change. C ould i fix it with a simple capacitor or resistor or there is more to it? 73 S53ATT
It won't be very stable on an SSB receiver. But on an AM receiver the drift should be less noticeable. Voltage regulation, shielding, better tuned circuit parts and more buffering can all help make it more stable.
@vk3ye Thanks Peter, but I explained the problem not good enough, I'm sorry, my bad. I actually meant how to solve the frequency deviation problem, as it is too high (FM) in the transmission instead of AM. I see you put a120k resistor and said it helps improve the audio aka reduce FM and provide cleaner AM. Seems like your circuit was still acceptable, in mine there is really too much Frequency deviation (Allthough I copied your circuit 100%; no modifications. The values are completely the same)
Not AM transmitter. Just a linear amplifier on a FM transmitter. No AM modulation here. The interface with the antenna is very poorly done as well. There is no impedance matching of any kind. Clickbait?
I´ve been following your channel for quite some time now, and I really appreciate it that you differ a lot from many of the hams out there. Hams on youtube mostly have one topic... It´s either Transceivers (+ them making a video about DX contacts) or Antennas... You make amateur Radio interesting to a wider audience by not showing these contacts (you do aswell, I know that) but also showing practical... beginner friendly... circuits that people can rebuild and will be able to get satisfying results... even with simple circuits. You´re lucky to have your amateur radio rules, because here in Germany (to my and my friends knowledge) AM is not allowed on 160,80,40... it is only allowed (HF wise) on 10meters... same goes for FM, and that makes a lot of easy do able experiments basically impossible... what does keep me and some friends away from the ham radio licence "do it for ... what?" (Also it´s very pricy here). Anyhow... about your circuit. The "motor boating" has nothing to do with the 10nF capacitor "long wire". It might give you a few nH, which are basically like "non existent" on these low frequencies. Your motor boating comes from RF "sneaking back" into your 1 transistor microphone amp, which then demodulates it, and modulates the transmitter with it... it starts to oscillate, and the sound you showed is the result. Add a 10...100nF Capacitor from base to ground (audio amp transistor) and there shouldn´t be any motorboating even with bad ground connection. I doubt it´s RF wise motorboating because you just have 1 stage after the oscillator. Also adding a 100nF in parallel to the 33R resistor can indeed improve the transmitter´s output power. Like you said, matching is important, but the problem with MF Frequencies is the hughe "inductive" current you get in the PI filter´s loading coil. Am into transmitter design 2 decades long, and building a 1W+ AM transmitter is an easy thing for me, but when matching the antenna... I realized that the loading coil eats a lot of power. At 1W, the inductors you use would "overheat and short internally" (Even far taller and far more expensive fixed RF chokes do get hot enough that you can´t touch em anymore and that just at 1W Tx power)... I use air wound coils with rather thick wire, that fixes it. The range depends on the antenna and grounding, like you hinted it. I used a 20 meters Antenna in one test, with a 2W (non modulated, PeP was higher) homemade transmitter on about 1250KHz. Ground is "Water pipe" from room heater. I didn´t make a full range test, but with a simple radio (not really a good receiver, but also not a poor receiver - it´s weakness is the small ferrite antenna as the whole receiver is tiny) I could pick up the signal a good kilometer "listen able" (understand what is being said without having to concentrate at the information). Anyhow... keep up the good work. I don´t know many "ham" youtubers that do stuff like you... on one side show ham radio realted stuff, but then show "DIY" electronics good for newbies. My friend also had rebuilt your ssb transceiver... but due to strict laws in Germany, he can´t use it even if he had the amateur radio licence (to low sideband supression -40 or -60 dB (super high) vs -15dB in other countries).
How you approach building a transmitter in a thorough and thoughtful way, stage by stage is very helpful
Please keep expanding on the AM circuits. Really fun and interesting content. Thank you from VK2.
Very nice to see how you can make something good with simple things,
I hope he will soon also make the hf stage really AM modulation!
Healthy and Friendly Greetings from the Netherlands!
Rob
Good base of knowledge and well explained.
Waiting before upload.. Love ur Rf work
Nice circuit. 1w AM can go very far with a tuned dipole antenna. I think the receiver side is the key to get weak signals from very far away.
Another really interesting video on the subject of AM transmitters Peter. I have put a couple of my failed experimental transmitters on the shelf due to this motorboating feedback problem which has crept in. My first transmitter would work well then suddenly burst into oscillation, a real pain which got the better of me. Interesting to see how you cured your problem. I like the idea of a crystal controlled transmitter as most AM nets have a fixed frequency. I am following your AM experiments with great interest...David M0DAD
I am building one of these. Cheers from G1BKI. Mick(George)
Great job !! Thank You for sharing...
Great selection of videos. I am currently making one if these basic transmitters. Building it on veroboard, strip board. Going to insert a small audio transformer in place of the 33ohm resistor. Also going to use a 386 audio chip for am modulation. Keep up the good work. Ps I may do a video if it works. Cheers from old George
I would suggest starting any transmitter project in a metal box with an antenna socket, even if you use this method of construction, housing it in a shielded enclosure will yield better results. A biscuit tin has depth and plenty of room. 73 de UK M0.
Good ❤
A BD139 is a good idea and to modulate the BD139 amplifier a IRF 510 could be placed from emitter to ground. This should give true AM.
Great
If you had a small 1k to 8 ohm transformer could you collector modulate, that amplifier stage?
Quite possibly.
Altough it would produce AM (technically) it won´t work because the Base-Emitter capacitance (+ others) will generate a feedback to the oscillator and still cause parasitic FM. It would give better AM than the current circuit, but I highly doubt it would be useable practifcally. You´d still have to tune the radio to the side of the main frequency. You´d need to add at least one buffer stage between oscillator and your final amp (if you want to keep that simple oscillator circuit in your project) to prevent the parasitic FM from occouring.
After I posted that, thought it may be better in the emitter. Yes agree with the buffering to reduce FMing. A small handful of parts could make a almost usable AM tx. A quick check on a SDR or analyser could show whether it's effective.
After I posted that, thought it may be better in the emitter. Yes agree with the buffering to reduce FMing. A small handful of parts could make a almost usable AM tx. A quick check on a SDR or analyser could show whether it's effective.
I made the circuit from part 1, but got a real lot of Frequency change. C ould i fix it with a simple capacitor or resistor or there is more to it? 73 S53ATT
It won't be very stable on an SSB receiver. But on an AM receiver the drift should be less noticeable. Voltage regulation, shielding, better tuned circuit parts and more buffering can all help make it more stable.
@vk3ye Thanks Peter, but I explained the problem not good enough, I'm sorry, my bad. I actually meant how to solve the frequency deviation problem, as it is too high (FM) in the transmission instead of AM. I see you put a120k resistor and said it helps improve the audio aka reduce FM and provide cleaner AM.
Seems like your circuit was still acceptable, in mine there is really too much Frequency deviation (Allthough I copied your circuit 100%; no modifications. The values are completely the same)
@@PatrikS57AP Wind the audio gain back. Use a higher value resistor in the supply connection for the electret microphone.
@@vk3ye Thanks!
Not AM transmitter. Just a linear amplifier on a FM transmitter. No AM modulation here. The interface with the antenna is very poorly done as well. There is no impedance matching of any kind.
Clickbait?
All mentioned in the video.
@@vk3ye You made a mistake and put "AM" and not "FM" in the title.