tunercoil

[ghoattriple]

Ok i have read on the internet for a while now that you make an tuner like in the pic.I have seen plenty of picures and they dont make sense to me so,My question is how do you hook this up to a transistor to start blocking out unwanted signals.and how is the tuner in the pic different from an FM tuner???they sould really post more abought this stuff on the net.I was unable to find what i wanted to no so i turn to you guy's.

 

[TheOne]

pic? Is there suppose to be a picture attached or are we talking about pic micro project?

 

[ghoattriple]

ok

sorry bought that i had to redo the pic it was to big.Here ya go

 

[TheOne]

OK, this is a parallel tuned circuit. The frequency of interest will be determined by F=1/(2*Pi*[SQRT(L*C)]) where L is in Henry and C in Farad. This means that at the selected frequency there will be a high resistance (impedance in AC terms) from the top of the coil/cap to the bottom of the coil/cap. All the other frequencies will be shorted out to GND (the bottom of coil/cap should be connected to GND)

If you want to amplify the signal, normally a small capacitor is used to feed the signal available at the top of L and C to a amplifier stage that will not load this tuned circuit i.e.. it must have a high input impedance, and for that reason a FET is often used or a tap near the bottom end of the coil where the impedance is lower to drive a bipolar transistor amplifier stage.

This is a very crude and basic explanation and you should be able to find volumes on this and how to design on Google like the one's below

**broken link removed**

**broken link removed**

 

[JimB]

Try googling "crystal radio".
You will find LOTS of information.

JimB

 

[zachtheterrible]

hi ghoatripple, i luv working on these little FM transmitters too. try searching this forum by typing in FM transmitter in search. you'll find a lot of postings by me in my trying to understand this thing. as well as others trying to understand these too.

also, go to radioshack and get "basic communications electronics". i think its a really good book for understanding amplifiers and oscillators (even though i don't fully understand them yet).

if you havent already BUILD IT!! it really helps to have hands on. and when it doesn't work, we'll give ya a hand :lol: