Your first radio transmitter can now talk

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Getting a simple 1 transistor CW transmitter to talk. Modification adds an LM386 audio amplifier as a modulator to transmit AM voice.
Contents
0:00 Introduction
0:16 How to voice modulate a CW transmitter
2:23 Need an audio amplifier to modulate
2:57 Audio amp diagram
4:59 Electret mic
7:26 Modulator and connecting to the transmitter
10:42 Wiring
11:48 Testing
14:47 Alternative crystal frequencies
15:13 What if it doesn't work?
15:49 Connecting a mobile phone with a voice loop app
16:29 Range test outside
16:57 On a web SDR
18:53 On air reports
19:00 Conclusion
If you haven't done so please watch Part 1 first: • Your first radio trans...
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Опубликовано:

14 июл 2024

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Комментарии : 51

@perfectomprg 5 месяцев назад

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

@roogalater 2 года назад

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 2 года назад

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 2 года назад

@@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.

@electronbox 2 года назад

Cheers Peter, enjoying the simple but effective circuits.

@joeblow8593 2 года назад

Nice project, thanks from the U.S.

@RevGunn-jq3cq 2 года назад

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

@TheArtofEngineering 2 года назад

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

@owenvinall9970 2 года назад

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

@vlfreak 2 года назад

cool project, thanks peter!

@letitrotfuckit 2 года назад

good job! I built on a s8050 transistor, what antenna do you have for the 80 meter?

@trcwm 2 года назад

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

@PaulaBean 2 года назад

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

@vk3ye 2 года назад

Any oscillator is a transmitter so why not?

@PaulaBean 2 года назад

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

@AllThatInterestingStuff 2 года назад

@@PaulaBean 555 timer outputs square waves, and its frequency is 500-kHz to 2-MHz.. not ideal for a transmitter..

@howardlevine7123 Год назад

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

@flexairz 2 года назад

What about the spectral purity of this design?

@vk3ye 2 года назад

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

@NELSONTHEBEST100 21 час назад

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 18 часов назад

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

@NELSONTHEBEST100 17 часов назад

@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.

@davkdavk 2 года назад

Could you do a small linear amp as well??

@leonardoelias22 2 года назад

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

@davkdavk 2 года назад

@@leonardoelias22 Would be a cool project.

@Hammerjockeyrepair Год назад

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

@snarfusmaximus 2 года назад

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 2 года назад

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 2 года назад

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

@pallabsikder3626 2 года назад

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

@DanielBerzinskas 2 месяца назад

1 MHz and low power for AM in US.

@danielraducu9073 Год назад

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

@vk3ye Год назад

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

@danielraducu9073 Год назад

@@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 Год назад

@@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 Год назад

@@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 Год назад

@@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

@TheArtofEngineering 2 года назад

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.

@AllThatInterestingStuff 2 года назад

I wonder why my comments get deleted.. What's wrong with the idea to use basic components for the Audio Amp / Modulator instead of the LM386 IC?

@vk3ye 2 года назад

I did not see those comments. Must be something wrong with RU-vid.

@AllThatInterestingStuff 2 года назад

@@vk3ye Thanks for the response, probably they got deleted because they had a link to a schematic image. Anyways, if there someone interested in an other audio amp for the electret mic w/o the need of an IC, search for "Mini project: Amplified electret microphone" (YT channel: bitluni)

@ok4rm 2 года назад

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

@cejaybee 2 года назад

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

@AllThatInterestingStuff 2 года назад

I don't care about the thumnails, I care about the content.

@cejaybee 2 года назад

@@AllThatInterestingStuff 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 2 года назад

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

@cejaybee 2 года назад

@@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 2 года назад

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