Your first radio transmitter can now talk

[@roogalater]

Peter, you'd get much greater modulation depth applying that audio to the base. Better yet, Pin 5 of the LM386 hangs at around half supply voltage and swings above and below that with audio. So, connecting pin 5 to the base via a resistor would vary the bias with the audio waveform. This trick works particularly well with the type of transmitter you've shown using the IRF510 or IRF530. If you power the LM386 with a 5V regulator, pin 5 sits at around 2.5 volts: the gate voltage range the IRF510 and 530 start to conduct. Apply pin 5's voltage to the gate via a 10 or 20k pot's wiper via a 1k resistor, with one end of the pot to ground, the other end to pin 5 and advance it until the audio sounds the best. You get good quality AM this way, with a bit of care. 73 de G0IFI

[@vk3ye]

Thanks. I have built another rig using Pin 5 of the 386 to drive a final RF amplifier transistor. Worked well for a 500mW transmitter on 1.8 MHz AM. But you can blow up the 386 if you don't use a current limiting resistor (4.7 ohm from memory) in series.

[@roogalater]

@@vk3ye Yes. You could use pin 5 to drive a reasonably hefty NPN device to series modulate the PA, of course. put an RF choke on the emitter and power the PA transistor through that device. But I've made a couple of transmitters with IRF530s in the final and the method of biasing the IRF530 with pin 5 of the 386 produces very fine audio, if you get the level right. It's a very simple and economical way of getting 100 percent modulation.

[@grzesiek1x]

It works quite well as Peter showed (modulation is something like 50 % maybe but it is enough in my opinion), through the emitter though:) I have just built the circuit. I had some problemes with the crystal, it resonated in different frequency and after applying a filter at the output (at the collector) it moved back to its fundamental frequency. I am not sure if it was because of the quality of the crystal or something different (I have ordred some other crystals and will test it as well)

[@electronbox]

Cheers Peter, enjoying the simple but effective circuits.

[@joeblow8593]

Nice project, thanks from the U.S.

[@perfectomprg]

This should be a mandatory video for ‘preppers’ to watch :)

[@RevGunn-jq3cq]

The two videos on this circuit are absolute gold! Thanks so much.

[@TheArtofEngineering]

You sir are the homebrew mad scientist!!! This ex ships RO loved this post!!! 73 analogue will never die!! Long live AM.

[@ezalb9893]

Hi, i found your video really interesting. i want to build this transmitter but i have a question: wich is the minimium size of it? i don't 40m of space... ...and, is there a simpler circuit for transmitting voice over 1Km or less?

[@vk3ye]

Check out my FM wireless microphone videos for something that goes a few hundred metres with a small antenna. Or consider 7 MHz. QRP AM is however far inferior to QRP DSB so consider DSB. But start with CW as it's simpler and goes a long way.

[@NELSONTHEBEST100]

Hi, friend! I have a question: is a low power operacional amplifier (as the LM386) really necessary, to get 100% of amplitude modulation, in this circuit? I tell this, because the transmitter is a small power one, whose oscillator is the only RF stage; so, I think that another op amp, wich has too lower power consumption (as a TL081 one), would also modulate this oscillator, taking it to 100% modulation level.

[@vk3ye]

A TL081 is much lower power and would likely need to drive a couple of transistors to work effectively here.

[@NELSONTHEBEST100]

​ @vk3ye , thank you! I've got it! I was thinking that a simple pre-amplifier could excit this oscillator/modulator, 'cause more powered audio amplifiers, generally, are requested in the output RF powers of the transmitters, normally in the last stage, coupled by an audio transformer.

[@PaulaBean]

I wonder if a 4066 quad lateral switch IC could be turned into an transmitter. It can oscillate, I think.

[@vk3ye]

Any oscillator is a transmitter so why not?

[@PaulaBean]

@@vk3ye Hmmmm... then in theory, also a 555 could be used to build a transmitter.

[@owenvinall9970]

Thanks Peter. Your video's are continuing to increase my Amateur knowledge. Owen Vk5kov

[@davkdavk]

Could you do a small linear amp as well??

[@leonardoelias22]

5w linear amp for less than 1w rigs... now we are talkin 😂😂😂

[@davkdavk]

@@leonardoelias22 Would be a cool project.

[@Hammerjockeyrepair]

he could do an irf510-520 circuit along with that one there with maybe 8 more components and see around 10watts

[@snarfusmaximus]

Up the power, improve modulation and pop it on 7125kHz? Great video, by the way. I've been playing with tiny AM transmitters a lot lately, but on MW frequencies to play music on my old radios.

[@vk3ye]

You could but don't think it's worth it. Need way more power than 500mW unless the receiving station is in a very quiet location.

[@davkdavk]

@@vk3ye I got a contact into VK3 from VK5 on ft8 with 100mW into an End Fed antenna on 40m.

[@flexairz]

What about the spectral purity of this design?

[@vk3ye]

Add another one or two pi network filter sections if you find harmonics excessive. A previous video describes a stand-alone low pass filter.

[@TheArtofEngineering]

AM low talk power but fun! Next instalment might be a final RF stage PA … or a VFO ?? Or could just build the BEACH 40.

[@danielraducu9073]

how would the schematic change for 27 mhz ? (component values) i assume crystal and output capacitors ...coils...

[@vk3ye]

Hugely. You'd need a different oscillator circuit as 27 MHz crystals are typically 3rd overtone. I used fundamental crystals here.

[@danielraducu9073]

@@vk3ye would you make a video about it ? that would work with the receiver 27mhz AM, that you made in another video(super regen mixed with charles kitchen design) ?

[@vk3ye]

@@danielraducu9073 I have no plans to construct or do a video on on this. Look up cheap walkie talkie circuits for an idea of how this is done.

[@danielraducu9073]

@@vk3ye what is so special about this 27MHz crystals 3rd overtone, i assume it s about harmonics but i am a full noob, please teach me

[@vk3ye]

@@danielraducu9073 It's not something that can be explained in a few lines here. Do lots of searching and reading on the different oscillation modes of quartz crystals. Eg www.industrial-electronics.com/crystal_osc_5.html

[@pallabsikder3626]

hey vk3ye can I make the transmitter with 11.059 mhz crystal? or other Crystal

[@DanielBerzinskas]

1 MHz and low power for AM in US.

[@vlfreak]

cool project, thanks peter!

[@howardlevine7123]

Use an audio transformer on the B+ side that will work much better use an audio transformer, the couple the audio

[@trcwm]

1 transistor for the RF part, a gazillion for the AF. 😱😃

[@ok4rm]

LM386 needs too many parts... I prefer TDA7052, it is minimalistic.

[@cejaybee]

Can't stand the Facebook-level clickbait custom thumbnails. The last few years have made me instinctively ignore videos with them.

[@cejaybee]

@Bence Bujdosó Prob is, too many people assume there is content going only by the thumbnail and spam that sh*t everywhere without actually watching the video first.. just as the SEO'er intended. (Shout-out to Hayden!) When the thumbnail is just a guy in pair of shorts, you're going to check first before bothering everyone..

[@HamRadioDX]

@@cejaybee I always enjoy a shout out… good or bad I guess

[@cejaybee]

@@HamRadioDX Someone showed me that message of yours trying to drum up a personal army on FB that omitted that a dozen over Redditors were calling you out of spamming and the clickbait thread had a 9:1 downvote:upvote ratio. Classy.

[@HamRadioDX]

@@cejaybee Redditors are a hard bunch to please.. I just have fun making videos on the hobby I enjoy,

[@vk3ye]

@@HamRadioDX A friend has advised me that Reddit is just a noise we tell kids that frogs make.