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How can I construct my own Fm circuit

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haitham al-saab

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Hello every body
I want to now how can I build my own Fm circuit , I now there is a lot of prepared circuit but I want to build my own .
I will be glad if you have any book or link that can help me , I already finish my electronics course and one communication course , but unfortunately I'm not able to construct this kind of circuit in these courses we just study how diode, Bjt and transistor works and a simple things about fm am .. etc and we used to solve a prepared circuit and that is it . I really fell shameful that I can not build my own design :(
 
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haitham al-saab said:
Hello every body
I want to now how can I build my own Fm circuit(
Click to expand...
This student does not say if he wants to make an FM receiver, an FM transmitter or both.
Maybe he cannot buy the parts anywhere.
 
The crystal radio receives 1MHz AM broadcasts, not 100MHz FM broadcasts.
Today, modern cities have too many AM radio stations so a crystal radio will have interference from most of them. Strong local stations will be too loud and weak distant stations will be faint.

The RadioShack Special is a super-regen circuit that also receives AM but at 100MHz. It is tuned to one side of an FM radio station and receives distorted audio and static interference by "slope detection" of the signal.
 
Hello guys
Thank u very much
but you gave me something that I do not hear about it at at all
my problem is:
1- I don't have all the component (capacitors , resistors ,.. etc)
2- I don't have a deep understanding about the circuit and the way that it is work exactly ,what I know is just the main idea but I do not know how do they put the value of C and R and why they connected in this or that why
In summery :
1- I want to have my FM design
2- I want to chose the value of C and R
3- and the way that the circuit connected

it is just a simple project I want it transmit within just 10 or 20 meters ,so I think it is not complected , and I think that there is no need for the devices that you mention it above

Again and again and again Thank you very much and thank you for your patient and your quick response
 
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There are hundreds of simple FM transmitter circuits on the internet. They are all almost the same. Some use only one transistor and a few other parts.
Since you do not have the capacitors and resistors then buy a kit that has them all.
 
thannara123 said:
Better one to making by using IC.
Click to expand...
Rohm made a very nice FM stereo transmitter IC about 10 years ago but it is not made anymore.
I do not know any semiconductor manufacturer who makes an FM transmitter IC today.

Chinese companies make millions of MP3 to car radio FM transmitters but their IC is not sold in small quantities.
 

Many cell phones have a tiny FM stereo radio circuit inside. But an FM stereo transmitter circuit is difficult to find.
 

In summery :
1- I want to have my FM design
2- I want to chose the value of C and R
3- and the way that the circuit connected
Click to expand...
If you want to design your own FM transceiver you first have to learn the basics of electronics. If you master those you start learning about RF.

Just start with building an existing 1 transistor FM bug for 3 meter (88-108 MHz)
Be carefull, the most simple circuits are the hardest to get working. If your capacitor or coil is to big or small, if paracitics are to high you think it does not work while in real it could be you are transmitting in the airtraffic or army band. In some countries penalties for illigal transmitting are very high. So inform your self about that and do not use an antenna. Radio signals can go, under the right conditions, much further as you think.

Do you have a > 100 MHz scope and LCR meter ? Or a scanner, spectrum analyser, counter or other instrument to check your transmitting signal (on harmonics and frequency of the first harmonic ?
 

Audioguru said:
Many cell phones have a tiny FM stereo radio circuit inside. But an FM stereo transmitter circuit is difficult to find.
Click to expand...

Building of FM transmitter is very simple .. with a single transistor (not stereo)
 
I built a simple one-transistor FM transmitter 51 years ago when I was a teenager. The schematic and parts list were in an electronics magazine.
It worked pretty well with a range of about 1 city block.

Then I studied electronics.
About 8 years ago somebody posted an 2-transistors FM transmitter circuit in a forum and said it didn't work. I analysed it and fixed its problems then it worked very well with a range of more than 2km.
 
On a Dutch forum a certain bug caused a lot of regular returning questions. Because it was very simple a lot of starters tried to build it. But it was not a great desing and very sensitive for small mistakes,
Because of this I decided to build it so I was able to give better help.

After that I started improving it just for fun. I'm a HAM and I have never transmitted illegal but pirates do not care and build those things so I tought if they do, then it will be better if they cause less problems if it works good and is clean., a group of regular forum visitors also started experimenting. The result is on my site: , https://www.pa4tim.nl/?p=1528 The schematic from origunal and improved are there. The original is like most bug more AM as FM. The improved is still very simple but true FM, much more stable and has a LPF. Most unfiltered bugs have harmonics upto 1-1.5GHz
Range on a dummyload with 30 cm wire attached was 200 meters transmitting from my shack and measuring outside with my house (stone, about 15 meter long) inbetween me and the TX. More as I expected.
 
thx a lot guys I really want to be like you in the nearest future :)
 

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