What about the 72mhz transmitters? I just need to know how to make a simple transmitter + receiver which i can then plant into an rc vehicle. This is jsut to learn and its not for long. I am buying a real transmitter system but i just want to learn how it works and how to build one and modify to do what i want to do.

Any help would be appreciated.
Thanks.

 

A simple transmitter and receiver are junk.

__________________
Uncle $crooge

 

Thanks audioguru, your transmitter will make a good project...

 

Audioguru,
Do you have a coilless 27 Hhz AM transmitter schematic, I mean with X-tal. My experience, I have that schematic that was very simple but I lost it. My current project is building a 27 Hmz walkie talkie. Can you help me?
Thank's.

harries

 

Every transmitter that I have ever seen except one, uses coils and capacitors in a tuned circuit to reduce harmonics that cause interference at other frequencies. The one that doesn't use a coil operates from the 9th harmonic of a 10.7MHz ceramic filter. It is very low power so its other harmonics don't cause too much interference.
Transmitters with a crystal also use a tuned circuit with a coil.

I just looked in Google for Walkie Talkie Circuits and found a few. It even had a link to a thread here about walkie talkie circuits.

__________________
Uncle $crooge

 

Audioguru,
I spent alo of times in Google for that, but not found yet. Ok now I understand that. Actually, I have a walkie talkie schematic attached. Receiver and oscilator coils are from 0,5mm on oscilator coil 8mm with 9 turns. RFC is from 0,5mm on 0.5cm free air coil with 33 turns.


my problems are :
1. I don't have a 27Mhz signal generator to tune that circuit. Can you help me?
2. The sound modulation is very low. How to solve this problem?
3. How to increase the distance?
Thank's for help.

Attached Thumbnails

 

 

Your walkie talkie doesn't work well because it is cheap.
Its parts cost about $2.00. It cannot be tuned.

The schematic has an error: The collector of Q1 is supposed to connect to something with negative DC on it.

__________________
Uncle $crooge

 

Dear Audiguru,

I would like to build your FM Transmitter, but I have the dificulties to find transistor 2N3904 in my town. I would like to substitute Q1 with C829 for preamp mic, Q2 with C930 and Q3 with C930 or C1970. Is it possible to do?
Thank's

 

Try the 2N2222A, those transistors you suggested sound really old.

__________________

I do not answer private messages asking for help because no one else can: benefit from advice I may give or correct me if I'm wrong.

Please ask on the open forum if you have a question and I'll be happy to help, if I know the answer.

 

The 2N3904 transistor is extremely common. Maybe it is not available in the Orient. A BC547 is almost the same but its pins are reversed.

The old Yapanese transistors are completely different.
The max allowed collector current for the 2SC930 is only 30mA.
The 2SC1970 power transistor has a huge range of hFE from 10 to 180 and its capacitance is too high.

__________________
Uncle $crooge

 

2N2222 sounds common for me. I'll try to find it. And is it possible to modify it as a PLL Transmitter with the PLL module from http://www.pira.cz/enpll.htm? How to connect it inside your Transmitter?
Thank's for help.

 

My FM transmitter does not have a voltage-controlled oscillator. Usually they use a varactor diode which is tuned with the output voltage from the PLL circuit.

Why don't you make a kit or make your own Micromitter? It has a quartz crystal and a PLL and it is stereo.
http://electronics-diy.com/schematic...ransmitter.htm

__________________
Uncle $crooge

 

Older thread -newer question

How long is the red wire antenna on your transmitter audioguru?f
From the point of attachment to the board.

Have you experimented at all with a very fine wire which will tend to sharpen the bandwith

__________________
My Property and my Family are not for Govenments to control.That is not the purpose of Governments.
To stop corruption in Government officials give them three times the penalty. They should, and do, know better. Let them commit to that when first employed

 

I tried it with a quarter-wave length. 80cm.

The tuned circuits and the amplitude of the modulation determine the bandwidth, not the wire gauge of the antenna.

__________________
Uncle $crooge

 

I take it you are not a radio ham?
Wire cross -section of the antenna is quite a factor at HF

__________________
My Property and my Family are not for Govenments to control.That is not the purpose of Governments.
To stop corruption in Government officials give them three times the penalty. They should, and do, know better. Let them commit to that when first employed