Some More Simple FM Transmitters

[leejongfan]

Hi all,

I am going to construct the FM transmitter according to following schematics using veroboard : Miniature FM Transmitter #4 from Atoon website (the right most pictures in the 1 post of this thread)

As far as I know, components layout is very critical in RF circuit. Anyone has experience in this, please help.

Your support would be much appreciated. Thanks!

 

[audioguru]

I am going to construct the FM transmitter according to following schematics using veroboard : Miniature FM Transmitter #4

It is not a good FM transmitter:
1) Its antenna is connected to its oscillator so its frequency will change if something gets near the antenna or moves away.
2) It doesn't have a voltage regulator so its frequency will also change as the battery runs down.
3) It doesn't have pre-emphasis (treble boost) like all FM radio stations so the de-emphasis in all FM radios will cut the highs and sound like a stereo with its treble tone control turned all the way down, or like an AM radio.
4) It is mono, not stereo like a Micromitter.

I made the very simple circuit about 45 years ago. Its performance was poor.

 

[leejongfan]

How about the Miniature FM transmitter #1 (Atoon website)
Let's say actually I don't really concern about sound quality as well as power supply, then are there anything else I should pay attention to?
For the antenna problem, do you mean I should place the atenna far way from the trimmer capacitor?
Thanks!

 

[audioguru]

The antenna of the very simple FM transmitter is connected directly to the oscillators tuned circuit. Anything that gets near the antenna or moves away changes the capacitance at the antenna and at the oscillator's tuned circuit which changes the oscillator's frequency.
My FM transmitter has an RF amplifier between the oscillator and the antenna so its frequency does not change.

It doesn;t have a voltage regulator like my circuit so you must retune it as the battery runs down.

 

[chilinski]

My FM transmitter is made on Stripboard. It is perforated and has parallel copper strips. The copper strips are cut at a hole then the remainder of the strip is used for another part of the circuit. The strips make half a pcb and the parts and a few jumper wires make the remainder of the pcb. Each hole has a single wire in it.

I'd like to see the backside of this. Would you post a photo of it?

 

[audioguru]

I'd like to see the backside of this. Would you post a photo of it?

I made my FM transmitter 3.5 years ago.
The stripboard is just 12 horizontal parallel strips of copper. Some of the strips were cut with a drill bit and so the strip was used for two or three functions. Eadh part has its own holes. A few vertical jumper wires are on the parts side of the stripboard. Most of the parts are also vertical.

 

[vinate]

Hi.
I built FM Well.
https://www.pira.cz/tx4.htm

 

[prabrahim]

Mine has a power amp stage and goes very far:

Sir,
Thanks for ur circuit,
does it work well
does it need an antenna

 

[audioguru]

Sir,
Thanks for ur circuit,
does it work well
does it need an antenna

I was not knighted by the Queen of England so I am not a SIR.

My Mod-4 FM transmitter sounds excellent, its frequency does not change when something move near or moves away from its antenna nor when the battery voltage runs down and its range is more than 2km to a very sensitive FM receiver when its 9V alkaline battery is new and there is nothing in between.

Of course it needs an antenna. It is a radio transmitter.
I never tried it without an antenna.
Without an antenna then its range might be across the street if it is in a plastic box.
I tried it without a battery but it didn't work.

 

[mvs sarma]

I was not knighted by the Queen of England so I am not a SIR.

My Mod-4 FM transmitter sounds excellent, .........
I tried it without a battery but it didn't work.

Nice reply Audioguru.

 

[Ammarjaasj]

thans alot

 

[transistor495]

Adding a 2N3866 stage will boost the power about 4times. A matching dipole antenna can provide a range upto 4km.

 

[mvs sarma]

Thereafter you will stop all the woks and attend police staions to attend court cases for illegal broadcasts/transmissions.

 

[transistor495]

I know it msv sarma. I have done it and tested it but now I'm using it without any antenna of course not even a short wire! I can receive signal within 200 metres circle without assistance of any cop.

 

[audioguru]

A serious problem with an illegal radio transmitter is the harmonics that cause interference to radio communications (ambulance or police radios?) and TVs.

 

[transistor495]

Previously when I was in college hostel, I have assembled one fm transmitter. My hostel room was near to TV hall. I was able to interrupt the TV signal completely with my transmitter when trimming to some particular frequency. So when my friends are enjoying TV programmes I could annoy them with my transmitter kept in my pocket making ON/OFF. When it is interrupted some person( TV operator guys ) will try to fix it on tuner. No result!
What I will do? I will go there and just touch on the TV same time I will switch off the transmitter. Wow!! I could here 'Well done,claps' from surroundings

 

[kandiraja]

i want to build a remote controlled(radio frequency) race car for my project i am a beginner so iwant entire list of components and cicuit to connect them help me please....................

 

[mvs sarma]

i want to build a remote controlled(radio frequency) race car for my project i am a beginner so iwant entire list of components and cicuit to connect them help me please....................

welcome !
why not purchase one?

 

[vanraj1]

Thanks i found some of very uewful porject to transmit FM if any one have FM reciver booster circuits diagram

 

[mvs sarma]

Thanks i found some of very uewful porject to transmit FM if any one have FM reciver booster circuits diagram

WELCOME !
How far is FM Transmitter from your location. Because, it is Line of sight and difficult to use amplifier, unless you get a signal by skip zone effect. You can get many of them if you google, but the antenna has be installed like multi element Yagi cut to frequency you are likely to get.