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AM or FM receiver schematic using electronic tuning?

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DaKandEKid

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I'm trying to build an electronically tuned AM receiver.

The circuit will consist of an AM receiver which contains the RF amp, the mixer and IF amp and a tuning circuit which would consist of a VCO, PLL and low pass filter.

I haven't been able to find a site which contains a project which contains a receiver done this way.

I'm trying to minimize the overall components and cost of the reciever.

It seems like many people have had to design a circuit such as this. Thanks for any info in advance.
 

hamfiles

New Member
I think I have one, but its not in electronic media, give me a day or two, and I will draw and post a schematic.


By electronic tuning, do you mean a servo, or what? The one I have is FM w/PLL and superhet mixer, tuned with a potentiometer varactor combo, but it can be adapted into an AM receiver.
 

hamfiles

New Member
Mine is manually tuned, but I suppose it could be modded for a microcontroller. I will post it anyway, it uses a varactor-potentiometer combo for tuner.

Closest thing I can think of to what you want is TDA 7084, it has push button tuning, continues to step up voltage feedback untill it locks, kind of like the many cheap walkman's that have push-button tuning. I'm not sure that qualifies as 'electronic' tuning, though. TDA 7000's series are simple superhet chips that use a very low frequency IF stage. Circuit I have uses the NE 602/AN 602 for mixer, then a PLL chip. I can't remember the # for PLL chip, but I have the chip. Probably you could look up the data sheet spec's for it.

Probably you could get ahold of a manufacturer's schematic for a commercial one. I'll look around and post back later.
 

DaKandEKid

New Member
Since my first post i came across that chip (TDA7088 i think is what you meant) and i am very interested in implementing a circuit in that fashion. I found a sample circuit at:
http://www.mikroelektronika.co.yu/english/product/books/rrbook/chapter4/chapter4b.htm

But, i don't know how to convert it to an AM solution the datasheet gives an example of how to do it with both an AM and FM solution but it uses a lot of external components that would raise the cost to much.

I'm not sure however if you converted it to an AM only circuit if it would require as many passives.

datasheet for TDA7088:
http://www.electro-tech-online.com/custompdfs/2003/06/TDA7088T_2.pdf
 
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