a more stable voice transmitter

Did the transmitter work for you?

  • Yes, it is completely stable

    Votes: 0 0.0%

  • No it did not

    Votes: 0 0.0%

  • There is nothing special about it

    Votes: 0 0.0%
  • Total voters
    0
Status
Not open for further replies.

mstechca

New Member
After countless hours of experimenting with transmitters, this one has proven to be the most useful, and I made it. It works great when the speaker is actually the output of my soundcard.

So far, it has been running successfully for 2 hours straight without me touching anything, and without an antenna. The receiver is about 1 meter away.

The battery used is the CR2032 lithium cell.

Do play with it all you want, but It is 100% stable for me.

Also, take the poll and let me know how it worked for you if you make it.
 

Attachments

  • fmtx.gif
    7.1 KB · Views: 1,632
Thanks for the Circuit.

Yes, It Works very Nicely.
I Modified some values Slightly, also added an a Electric mic.

This PCB is 1.3 Inches Square.
Tuning range about 92 to 98 Mhz, but depends somewhat on antenna length.

Think I'm going to add a preamp transistor onto the PCB.

Will post this PCB Later, if anyone want to ues it.
Can also supply them.
 

Attachments

  • xmitter-1.jpg
    67.4 KB · Views: 1,029
Hi Gary,
What is the range of your version of MStechca's transmitter using a 3V battery?
 
audioguru said:
Hi Gary,
What is the range of your version of MStechca's transmitter using a 3V battery?
Click to expand...

I didn't state the maximum range when I posted my transmitter, because I didn't physically measure it, but it works great at 2 meters range :lol:

and chemlec, adding the antenna at the tank circuit (at the transistor's collector) could degrade performance, especially when you hover your hand over it.
 
mstechca said:
I didn't state the maximum range when I posted my transmitter, because I didn't physically measure it, but it works great at 2 meters range.
Click to expand...
Hee, hee. :lol: Tweak it a little more and maybe it will go 15 feet! :lol:
I thought it would go across the street. Maybe your radio isn't sensitive enough.

Many radios overload with a transmitter nearby, causing you to tune your radio to a false overload signal instead of the real signal. When you tune the radio to the real signal from the transmitter then the range is farther.
My Sony Walkman radio overloads but has a local-distant switch that stops the false overload signals.
 
I got over 100 feet, but I was using 6 volts.

The Circuit operated ok from about 2 volts to 15 volts. However changing the voltage does affect the frequency a bit.

Edit: I Forgot to mention that there are absolutely NO AM or FM Stations recieveable, where I live. Blocked by the mountains on all sides.

Its Kinda Nice for this kind of expermenting.
 
hello there..

may i know how to convert the original circuit to be use with electret mic?
the circuit works ok (i think) because there`s howling sound in my receiver (radio), but i just couldn`t speak through it.
 
Last edited:
chemelec said:
The Circuit operated ok from about 2 volts to 15 volts. However changing the voltage does affect the frequency a bit.
Click to expand...

It can't be that stable then, if you want a stable transmitter then I suggest you try audioguru's design, it uses a voltage regulator for the oscillator to avoid this, also the frequency won't change with varying antenna length as it's isolated from the amplifier, oh and it has pre-emphasis so it sounds better too.
 
manz said:
may i know how to convert the original circuit to be use with electret mic?
Click to expand...
It uses a low impedance speaker as a microphone. An electret mic is fairly high impedance and won't work.

the circuit works ok (i think) because there`s howling sound in my receiver (radio), but i just couldn`t speak through it.
Click to expand...
Your howling is caused by acoustical feedback. The microphone can hear the radio and the same sound goes around and around. Stop the howling by separating the transmitter from the radio and turn down the volume on the radio.
 
audioguru said:
It uses a low impedance speaker as a microphone. An electret mic is fairly high impedance and won't work.
Click to expand...


so is there any ways that the electret mic can be use with the circuit. i just simply can resist a FM trnasmiter circuit project: ) and im not sure wether you can still remember me, you helped me a lot to make the transmitter of yours (mod 3 and mod4) some time ago.


chemelec said:
Yes, It Works very Nicely.
I Modified some values Slightly, also added an a Electric mic..
Click to expand...

so that`s why i asked how it is done. i believe he`s on vacation(stated in his website)

thanks a lot
 
audioguru said:
Your howling is caused by acoustical feedback. The microphone can hear the radio and the same sound goes around and around.
Click to expand...


i`m quite bad on describing sound. what i meant was that the sound is like the radio is recieving something out of that clear frequency while im adjusting the trimmer caps.but even so, i just couldn`t speak trough it. maybe due to the electret mic.
 
If the sound from your transmitter was clear, then its mic wasn't working.
An electret mic needs a resistor in series with it from a supply, to power it. Chemelec uses 8.2k.
An electret mic needs a coupling capacitor. Chemelec uses a 4.7uF capacitor.
Chemelec capacitor-coupled the high impedance electret microphone to the transistor's low impedance emitter which loads the mic's level down. It would work much better if the mic is capacitor-coupled to the higher impedance base of the transistor, like all other simple FM transmitters.
 

Attachments

  • Chemelec's FM transmitters.JPG
    91.9 KB · Views: 709
hmm thanks.. i`ll have a look at it, just need a little time to digest things up hmm thanks anyway.. ohh by the way, just need to know about the inductor, what are the different between self winding inductor and with that standard like resistor inductor. why some FM circuit need the be hand winding and some circuit can use that resistor like inductor? is it because the inductence value for the self winding is not there in the market?

thanks again
 
A hand-wound inductor for an FM transmitter is simple, cheap, is adjustable by spreading or removing turns and it works.
An inductor that is manufactured might resonate at a frequency too low to be used at 100MHz.
 
If you want to set the transmitter frequency as desired or free one you must have a possibility to change it. That can be done by trimming one of the elements in LC tank circuit. Situation can be fixed inductor (like a resistor or etched on PCB) and variable capacitor (trimmer) or a fixed capacitor and variable inductor.
 
Can the audio Input be a square wave from a 555 timer?

What type of capacitors did you use? It looks like Audioguru used Ceramics (NPO?)
 
Overclocked said:
Can the audio Input be a square wave from a 555 timer?
Click to expand...
Yes of course. Then the resistor that powers the mic isn't needed. The high level from the 555 would need to be attenuated down to mic level. Why make an FM transmitter that buzzes?

What type of capacitors did you use? It looks like Audioguru used Ceramics (NPO?)
Click to expand...
Ceramic disc capacitors are excellent for VHF radio circuits. I also used film capacitors for audio coupling. The power supply section has two 100uF electrolytics that are bypassed with ceramic disc caps.
 

Yea, a tracking transmitter. Its an Idea Ive wanted to test for a long time. Ive come up with the idea since my younger bro likes to get "lost" around the neighborhood. It would be a good way to "see" where is he is, Kinda like GPS, but for the receiver, I would use a field Strength Meter and a regular receiver.

Of course, this thread also gave me another idea, Essentially, It could be used with any Mp3 Player and be able to transmit without the need for wifi. That means I could build a stand alone computer, Put all my Mp3's on it, and Have it play continuously. Then I would also be able to receive it anywhere within the house, Or even Outside.

Is this transmitter AM or FM?

How did you make you Inductor out of PCB? Did you use Eagle to draw the PCB or some other program?
 
Overclocked said:
Is this transmitter AM or FM?
Click to expand...
AM sounds poor with distortion, noise, interference and no treble audio frequencies. Since its RF frequency is so low, a transmitter's antenna would need to be 100m long. Its inductor would be many turns of wire and needs a ferrite core.

How did you make you Inductor out of PCB?
Click to expand...
The inductor for FM at 100MHz is only a few turns of wire (or printed traces)with just air as a core.

Instead of making a mono FM transmitter toy that drifts its RF frequency, why not make a Stereo Micromitter that uses a modern IC with a crystal controlled frequency synthesizer and a phase-locked-loop for stability.
https://electronics-diy.com/schematics/BH1417_fm_transmitter.htm
 
Status
Not open for further replies.

Similar threads

  • Question
More "Maker" Oriented Forums?
Replies
13
Views
2K
tepalia02
T
  • Question
More than one controller for a PT100 3-wire element
Replies
0
Views
1K
Grossel
L
Controlling a Stepper Motor Valve with a DAC
Replies
4
Views
1K
Lapinrose
L
V
  • Question
Convert a single-phase motor to a three-phase
Replies
4
Views
1K
ZipZapOuch
J
  • Question
Testing a Capacitor Microfarad Rating that has a Resistor
Replies
7
Views
2K
Tony Stewart
Menu
Log in
Register
Cookies are required to use this site. You must accept them to continue using the site. Learn more…