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manatee
New Member
Portugal
3 Posts |
 Posted - Sep 27 2010 : 10:19:36 PM
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hi!
i'm trying to build this circut:
http://www.aaroncake.net/circuits/Fm_Radio_Circuit.asp
anyone tested it and know if it works?
i tryed to build it and didn't work. i have some experience with electronics but not with radio circuits.
i pluged it to my ear phones and nothing, tryied the computer speakers and didn't worked too...
any tips about the coil? it's the first time i tryied to build one and i'm not shure if i'm doing it right. i did not used copper wire, i used some silver wire that i don't know what is.
thank you for reading
and hope you can help me.
regards
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 28 2010 : 08:22:35 AM
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| The TDA7000 is obsolete and has not been made for many years. The TDA7088 replaces it and is used in the $1.00 FM "radios" sold at The Dollar Store. Their performance is very poor. |
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manatee
New Member
Portugal
3 Posts |
Posted - Sep 28 2010 : 10:46:51 AM
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i have 3 tda7000, so that is not the problem :D
my main goal is to build a simple FM radio reciver tunable by a potentiometer (or by voltage with the mv209) and this circuit looks to do the job, but i can't get it to work.
i will keep the trubleshoot, but i still don't know much about coils.
it's for an art project so the performance of the circuit does not need to be that good...
off topic: anyone know any radio chips that can tuned with a pot or voltage? instead of a variable capacitor?
thanks again |
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 28 2010 : 7:08:33 PM
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Any FM radio that is tuned with a mechanical variable capacitor can also be tuned with a varactor diode, an ordinary diode or one of the diodes in a transistor by changing the DC voltage fed to the diode.
Because the capacitance of a diode changes when its reverse voltage is changed.
Your FM radio probably will not work if you build it on a breadboard. It needs a compact pcb design. |
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manatee
New Member
Portugal
3 Posts |
Posted - Sep 28 2010 : 10:05:11 PM
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thanks! you answer was very helpfull.
makes sense, i built the circuit on a stripboard and it's not very compact.
i have another couple of questions regarding a very similar circuit with the tda7000.
this one: http://www.circuitstoday.com/single-chip-fm-radio-circuit
the circuit says that the coils are 56nh induction, but the explanation text says to build a 5 turns air coil.
can i use one of the ready avaliable coils?like one of this: http://parts.digikey.ca/1/3/56nh-inductance-coil
Or do i realy need an air coil?
smd it's not a problem since i'm going to design a compact pcb on eagle.
any advice on how to position the components on a pcb? the coil near the chip, or as far as possible? capacitors close to the chip on not?
sorry for all the questions, but i realy don't know much about radio circuits so i'm not very confortable with them.
once again, thanks a lot audioguru.
regards
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audioguru
Nobel Prize Winner
Canada
4218 Posts |
Posted - Sep 28 2010 : 11:12:19 PM
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All high frequency radio circuits use air coils. A purchased coil might not work at the high frequencies because its internal capacitance might be too high.
A short piece of wire is too long because it has too much series inductance at high radio frequencies.
Designing a high frequency radio is an art because you must keep wire lengths as short as possible but parts must not be too close together to cause capacitive coupling between parts.
It is best to use the pcb design shown on the datasheet and applications note for the radio IC.
But frequently these important papers are not available anymore for old obsolete parts. |
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tda 7000 radio reciver (help)
