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Audio input in FM bug

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anfegori91

New Member
Hello, i've made this fm bug transmitter:

FMBUG:D

It works perfectly with the electret mic, (I use it to listen to the tv in the night), but i want to connect it to my laptop or any other audio source to make a tiny radio station to get fun (and to eliminate the annoying feedback sound), but i don't know how to attach it in the circuit. Can anyone help me with this?


 

colin55

Well-Known Member
You are using one of the circuits I designed 20 years ago. I can tell my circuit anywhere.
Remove the electret microphone and 22k resistor. Connect the negative rail to the "ground" terminal of the "audio output" of the laptop and connect the 22n to the "audio out." Turn the volume down so the output is not overloaded.
 
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audioguru

Well-Known Member
Most Helpful Member
Annoying feedback sound is caused when the microphone can hear the speaker and the sound goes around and around. Use headphones that completely cover your ears and are sealed then the microphone will not hear them.

You can add negative feedback to the audio transistor with an emitter resistor, add a volume control and add two resistors to mix the stereo channels together.

Doesn't the frequency drift when something moves toward the antenna or moves away?
Doesn't the frequency change as the battery voltage runs down?
Doesn't the the receiving FM radio sound muffled without high audio frequencies?
Will it transmit as far as across the street?
 

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audioguru

Well-Known Member
Most Helpful Member
You are using one of the circuits I designed 20 years ago. I can tell my circuit anywhere.
You copied it from Radio Electronics magazine 1963 (46 years ago).
I built it then. It sounded awful like a stereo with its treble tone control turned all the way down.
 

colin55

Well-Known Member
Yes, you are right audioguru, I copied my FM Bug circuit from the 1963 Radio Electronics magazine. How clever of you.
By the way, please send me a copy of the circuit from 1963 Radio Electronics, as I have not seen the issue of the magazine you are talking about.

Colin Mitchell.
 

colin55

Well-Known Member
If you haven't kept the magazine and it's dated 1963, you must have a phenomenal memory.
I have to give you credit for such a brilliant.
I wonder why the 50,000 readers of my magazine, over the past 25 years, have not let me know where I have pinched all my projects from.
Surely someone else would have realized how crooked I have been, deceiving all my readers for this period of time, and making money out of them with such deceit.
 

Mikebits

Well-Known Member
If you haven't kept the magazine and it's dated 1963, you must have a phenomenal memory.
I have to give you credit for such a brilliant.
I wonder why the 50,000 readers of my magazine, over the past 25 years, have not let me know where I have pinched all my projects from.
Surely someone else would have realized how crooked I have been, deceiving all my readers for this period of time, and making money out of them with such deceit.
Is your mag still in print? Started in 81 no? Pretty cool to have a mag.


Since the image posted seemed to bother you, I removed it.
 
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audioguru

Well-Known Member
Most Helpful Member
Of course I remember my first electronic project, the FM transmitter. I know the magazine that I subscribed to for many years and I remember my age then and therefore the year of the project.

There must be hundreds of copies of exactly the same simple circuit on the internet today.
Colin, maybe you copied a copy of the magazine's project.
 

Mikebits

Well-Known Member
63 editions of Radio Electronics go for 10 bucks on Ebay. How bad do you want to be right? :)
 

colin55

Well-Known Member
Please don't promote the magazine. I don't have any issues left.

That issue of the magazine was typed by me on a phototypesetting machine, before computers came in. It was hand set, paragraph by paragraph, and stuck down on sheets, Every diagram was "taped" and each value was hand stuck on the page. The typesetting machine had one line on the display and you did not know what font or what size or what space you were using until you developed the film like a photograph. Then it had to be redone all over again to get the sizing and spacing right.
The TEC computer was designed by one of the staff but the explanations and layout and coding was mine. At the time, there was no other simple Z-80 computer that explained how to program in machine code. We sold over 1,500 TEC computers in a country with a population of 18,000,000.


There are still people wanting the Z-80 computer, that finished nearly 15 years ago.
 
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colin55

Well-Known Member
I copied the FM Bug directly. All the hundreds of prototypes I have in boxes of FM bugs, were just a "front" to impress the staff so that they thought I was actually designing the projects.
I didn't design anything. I just tricked everybody. I couldn't design a circuit for a torch.
 
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Mikebits

Well-Known Member
Please don't promote the magazine. I don't have any issues left.
Do you really think I would do that? I just thought that it was cool that you had the entrepreneurship to undertake such a task.
 
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Mikebits

Well-Known Member
ps. Ptttttttt
 

Sceadwian

Banned
Hire someone to sell them for your audio =) You can afford it, you're independently wealthy now!
 
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