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FM Radio


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Hello EDY,
you are correct. IC3 and its complementary componets are a just a sound amplifier and can be ommited. You can put the sound signal (taken from potensiometer's P1 wiper) directly into your's soundcard AUDIO input so that you can have totally digital control over your radio receiver.
(You realise ofcourse that tuning isn't exactly 'digital' but looks like it :o) )

The DOS software I have, is very old technology :( and has several bugs. If you want to look for something else, search for any freeware Parallel Port access tool on Google. You should find something...


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Weel it says it can be connected to the PC on the schematics but that isn't my goal. Just want to build a simple fm reciver.
Theres one thing bugging me.
In my car's radio you can chose between low and high pass (not sure is this exactly the term) but I havent seen it on any schematics.
I'll look the car radio later and tell you the frequencies it has.
P.S. it has AM parto so don't think I'm talking about that :)

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  • 3 weeks later...

Ok, you may use it as a simple analog radio receiver ;)

About the other matter, the "low-high pass", I can only guess for what you are talking about. I think you mean "tone control" which suppress or raise the low-high frequencies of the acoustic bandwidth.
Well this receiver doesn't have any of these 'whistles' because of it's simplicity. It is a mono (not stereo) FM receiver.

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  • 3 months later...

I build the FM Radio on a proto-board and I used a BB204B variable capacitor instead of BB329, but it didn't work. Anyone could tell me what modifications do I need to do in order to use the BB204B.
Thanks for any comment!

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  • 5 months later...

Dear AVRFreakMan:

Is correct, I cant tune any station. I will esperiment with coils.
What coil define tunning frecuency? L1 o L2?

If the radio is out of the comercial frecuency, How I can know if the radio is working and if the problem is only the coil?
Anybody know the value of the coils (uHy - mHy) ?


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L2 is the tuning coil.
Just make it: take a thin wire(0,6mm) and make 5 turns of 4mm internal diameter.

If it doesn't work try to stretch/squeeze it and if it doesn't work add/remove turns and repeat.(adding turns reduces frequency).

If no success, check the PCB and components for errors, or use a capacitor trimmer instead of the varicap, or search the internet and the datasheets of TDA7000 for other similar circuits.


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  • 1 year later...


Please tell me the equivalent in MicroHenry [uH] of "5 Coils linked with internal diameter 4mm from cupreous isolated wire 0,6mm" of inductor used in thsi project.

Also, please tell me that can we use the above inductor in equivalent Henry or we must have to make the inductor by ourselves.

Also, please tell me the lenght in cm of the inductors used in this project.

Thank you very much


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Sir i think u dint actually get my point. There are 2 types of inductors.

1.  That u make urself by using a wire of a certain lenght n thickness and making
ciols of it.

2. That u can get if u know the inductance of an inductor like 10uH, 0.1uH, etc. It looks just like a resistor. It does not have any coils.

The function of both is the same. I tried both while i was making FM transmitter. But only 2nd one worked. So, I just wanted to know if it is necessary to use a handmade inductor or we can use the one that looks like a resistor ( I dont know what to call it )


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An inductor that you purchase is a coil of wire, almost like the one you can make. It is wrapped in plastic , tape or something so it can't be adjusted and its value is in color bands on it.

A microwave inductor is a stripline, or piece of straight wire or rod and its inductance is determined by its length and thickness.

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  • 1 month later...

The new Philips FM radio ICs had tiny surface-mount packages and didn't have a tuning control. They scanned and stopped at the next station. They don't make the scanning ones any more, I guess because they were copied in China. They sell the new TDA7010 in a surface-mount package and it seems to be the same as the TDA7000.

My wifey got a couple of the tiny scanning radios for free by signing-up for newspaper delivery. They sound terrible and the signal must be very strong or the sound fades and distorts. I thought the bad sound was from the cheap earphones, but they sound excellent on my Sony Walkman and CD player.
I saw the radios at The Dollar Store selling for $2.00CAN complete with the earphones and two AAA battery cells. Oh yeah, the radios also have a cheap flashlight built-in.

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