FM transmitter (mod4)

[audioguru]

My FM transmitter circuit is only 1.3" x 2.0" and does not have long wires all over the place.

 

[transistor495]

7805 is a very noisy regulator. Sometimes it can be the problem.

 

[whiz115]

My FM transmitter circuit is only 1.3" x 2.0" and does not have long wires all over the place.

how did you arranged the components in such a small space? i don't believe you... since the coils alone accupie enough space.

 

[audioguru]

The photo shows it on a piece of stripboard that measures only 1.3" x 2.0" and has corners for mounting bolts.
Count the holes that are 0.1" apart.
I was lucky to find tiny trimmer capacitors.
One extra resistor (560) is on top but not connected to an LED.
The 47k resistor is on the bottom.

 

[whiz115]

measures only 1.3" x 2.0" and has corners for mounting bolts.Count the holes that are 0.1" apart.

indeed...

mine using SMDs is 1,25'' x 2,87'' but i deliberately spaced too much the components...

 

[Ghosty_Ghoul]

audioguru,
Could you please put labels linking each component on your board to the schematic on the photograph. I can guess most of them but it might help the noobs more.

 

[audioguru]

Here are the capacitors labelled:

 

[circuitnoob]

Two yellow wires connect the jack to the board...the other 3 connect the power section to the other parts. Well if 7805 is a noisy LDO what can i use instead of that and LM2931 (i have LM340). Also i noticed that the transistor connected to the 2nd coil gets quickly heated when a current passes through it.

 

[audioguru]

Something is wrong with the layout of your circuit to cause the output level of the oscillator to be low. Then the output transistor gets too hot.
Try using a 10pF capacitor as feedback in the oscillator instead of the 4.7pF for C7 shown on the schematic.

 

[Ghosty_Ghoul]

Here are the capacitors labelled:

Thanks.

What about the other components?

Is this right?
**broken link removed**

 

[audioguru]

What about the other components?

Is this right?

Yes, you are correct.
**broken link removed**

 

[Hero999]

That's good, I think I'll add that to the project on Silicon Tronics, unless you don't want me to, Ghost.

 

[Ghosty_Ghoul]

I would like that.

 

[chingyg]

I finished reading the thread, I will be building one soon, do you think it can cover a building, which is about 150m radius from the point of transmission?

BTW that guy who can't find the new thread button, hahahahahahahahahahahahahahaha. shame man.

 

[audioguru]

If the building is made with rice paper and bamboo then the transmitter will cover it if the radios are a high quality.
But a reinforced concrete or steel building will have poor coverage.

 

[chingyg]

Rice paper and bamboo, I'd love to live in there. but haha it's a brick building. let me find the dimensions on a map quick

Its just 50m radius, shouldn't be that bad now should it?

 

[audioguru]

The sensitivity of the radio determines the range of a simple transmitter.
Across the street or 2km away.

 

[circuitnoob]

hey dont laugh men people with less than 20 posts cant see the new thread button....(including me)

 

[chingyg]

The sensitivity of the radio determines the range of a simple transmitter.
Across the street or 2km away.

Ok, the receivers are all cellphone fm radio and good hi-fi's. etc.
But I'd love to have it running on a 12V lead acid battery. Do I just add a 7809 regulator or maybe leave it alone and replace Q3 with something thats a bit bigger?

 

[chingyg]

Can I use this as a power supply?
the Input is a wall adapter, maximum current 500mA, has a built in bridge rectifier and a 1000uF filtering capacitor.


Its the 12V output fine? or must I rather stick to 9V?