Creating a Walkie-Talkie with generic 433MHz RF Modules?!

Parts list (incomplete, see Instructables for more, affiliate links):
Aliexpress:

In this project I will show you how to use generic 433MHz RF modules from Ebay in order to create a functional Walkie-Talkie. That means we will compare different RF Modules, learn a bit about a class d amplifier and finally build the Walkie-Talkie. It can be powered by a normal powerbank for around 130 hours and features a range of around 15m. Let's get started!

Thanks to JLCPCB for sponsoring this video

Music:
2011 Lookalike by Bartlebeats

[KingJellyfishII]

The "and I will see you next time" has been slowly getting more and more enthusiastic over the years... Lol

[Asu]

Greatscott!: _"as you can hear, it still sounds acceptable"_ 8:17
The speaker: *demonic sounds*

[عبداللهصدقه-وك]

What i know that when you want to transmit an analog signal via a digtal transmmiter the first step is sampling the analog signal, and there is a condition to consider which is the sampling frequency must be as twice as the maximum frequency of analog signal, therefore if you picked a sampling frequency then you must make sure that the maximum frequency in the analog signal is half the sampling frequency, otherwise every frequency which higher than half the sampling frequency will be picked as noise.
Sorry for long comment.

[ElectroBOOM]

Question, the module was able to send audio range analog signals. Why not directly send analog through? modulating the analog to digital would require a much larger bandwidth.

[DoctorX]

8:34 I take it that you're not hearing the painful high pitched sound during the mike test... Oww, my ears

[TheWTFDubstep]

I'm still in hope of seeing you making one RF transmitter from scratch.

[Joeyhelmond]

Honestly, even though he's from Germany, his English sounds better then most of the people in Holland (like me😁). It's clear, I can understand it, and he talks slow!! Great Job Scott!!! Keep up the good work!

[lpt]

Not great, not terrible





that's what they said in Chernobyl when the radiation was 3.6 röntgen ( bud was 15000)

[divingquokka]

"You can hear that the music transmission was also successful" 7:45 I only hear beeping.

[sriharshakavuri]

That moment when Great Scott posts and you get to it 30 seconds later...

[Stefan]

I have read a bit through the comments. One person already suggested to use these moduls in their "analouge" mode. The transmitter is simmilar to one of these TTL oscillators. You simply can bridge the data pin to "+" from your supply, and series modulate it with a PNP or NPN Transistor. This will give you AM with FM. The FM Part is just narrowband FM, but on a selective receiver you´d need to use slope detection, but these receivers usually are "Super regenerative receiver(s)"



I´m mainly talking about the green circuit boards (the ones completely on the left side in your frequency test, that just could take 5KHz).


On the receiver there´s a two stage super regenerative receiver. One transistor works as RF preamplifier, to get the RF noise away from the antenna, whilst the other one is the actual receiver. On your modules, at least the RF preamp transistor is mounted - the modules I have, the receiver misses the transistor (probably were lower price due to this fact got them as a gift)


On the receiver board, the output from the super regenerative receiver goes to a lowpass filter hence it´s quench frequency (thats why you only can transmitt up to like 5KHz). The 8 pin SMD Chip - LM 358 - only forms the sine wave into a square wave.


You can "tap off" the signal from the receiver before the LM358 chip, and so you can make complete analouge audio transmission. All you need is a modulator + microphone amplifier on the transmitter side... and a small audio amplifier on the receiver side with "tapped in" audio pickup before the LM358.


Practically



- To get the transmitter to transmitt AM -


Bridge "Data" to "+ UB" and take a standard NPN Transistor. Use double supply voltage, and tap the transistor between
"-" of your transmitt module and ground. Now use a 1M Potentiometer, and a Multimeter. Connect the 1M Potentiometer between base and collector, and have it adjusted to "1M" at the start. Now decrease it´s value,
untill you reach about the half supply voltage on the module.


Via a 100nF capacitor and let´s say a 3, 3k resistor (random values) you can now put Audio on base of the transmitter.


The audio would already be received from the receiver, but it would be extremly distorted because the LM358 converts the sine wave signal from the regenerative receiver to a square wave signal.


Take an amplified speaker, hook one pin up to ground from the receiver module (while the transmitter is on, try with a low volume level on your phone with my suggested values) and use a let´s say 10k + 10...100nF (whatever is in the parts box) between "audio in" from your speaker and the connectors around the LM358 - one connection will be "audio out" from the receiver. If you find it, you will hear your music over the speaker.


Later if you want to use that "concept" you might need to add a lowpass filter between your receiver module and an audio amplifier Chip, because some remains from the receiver´s quench frequency might be left, and block / inteffer with the audio chip (very quiet, could start motor boating if connected to the same battery).


For the transmitter you don´t need to use the full voltage. If you lower the voltage the "AM percentage" will increase, whilst the FM percentage will decrease, but "good" AM will cost a lot of TX power (like going down from 10 to 0, 5mW)


Anyhow, since the receiver is a wideband super regenerative type, it won´t care about "that bit" narrowband FM, but
if you´d receive this on a more "proper" receiver, that has AM option, you´d need to use slope detection for it.


I´m talking about the green modules ... some other modules might use a more "fancy" "Superhet" receiver.



Regarding the 1M potentiometer... maybe a 250k might also work... I don´t know how these transmitters react
to overvoltage. TTL modules "can take some" but I´m sure it´s not good for them.


I´d appreciate it if you´d give this a try, but since my comment is just one of many... I´m not really expecting much

[nbenci]

Is it just me or "hh" inhaling/gasping sound increased at the start of each voice audio clip?

[akhurash]

To get rid of the 5kHz frequency, perhaps a band pass filter can be used... You can cascade the LPF with the 41kHz cutoff freq with a high pass filter > 10kHz or so

[bagassetiawan]

Thanks, Scott. It's inspired me to making wireless subwoofer. I don't need very high bandwidth rf module because my sub only need maximum 500hz.

[varunsreedharan]

I'm very impressed JLCpcb is still operating now. I bought 4 boards yesterday.

[felixcenteno]

You can transmit and recive analog signal (using the first pair TX/TX boards) if you bypass the comparator on the receiver, the 8 pin chip normally is a lm328 amplifier configurate in one half amplifier and the other half like comparator, this last one is what you need to bypass to get an audio signal

[OliverHynds]

I like the new new presenting style with more talking to camera! Good video!

[leozendo]

Either go full analog or full digital. Try out RpiTx, it works amazingly well. You just need to figure out a way to attach a microphone to the raspberry pi zero and you can transmit on 0-900Mhz.

[kienanvella]

if you want a decent range on those, you can get it by building yourself a dipole antenna to replace the monopole. I've even built a crude yagi antenna for use with modules like this, just with one guide element and one reflector element. there's some calculators around that can make it easier for people not so comfortable with antenna design to build their own antennas.

fortunately, these are relatively low frequencies, so you can be a bit sloppy with your antenna construction and still get decent results.

[yobalzal]

Have been following your channel since long & have learned a lot.

Always heard your voice but really pleased to see your face, great work man keep it up :)