digital radio

[andrew8485]

hello i have been learning about basic fm radio (complacated) and need some one to point me into the right direction, i want to find some info on how the newer radios work, the ones that when you push a button it scans thew the freuencys or to a memory frequency i tried to do a search but no luck on that topic. i know i can to it with a rotation know hooked on a var cap but how do i so it like new radios ,with the push of a buttion, can some one lead me in the right direction with a search idea thanks a mill

 

[Nigel Goodwin]

hello i have been learning about basic fm radio (complacated) and need some one to point me into the right direction, i want to find some info on how the newer radios work, the ones that when you push a button it scans thew the freuencys or to a memory frequency i tried to do a search but no luck on that topic. i know i can to it with a rotation know hooked on a var cap but how do i so it like new radios ,with the push of a buttion, can some one lead me in the right direction with a search idea thanks a mill

They work by using a 'varicap diode', this is a device whose capacitance varies as it's reverse bias changes - actually most rectifier diodes do this fairly well. There are then basically two ways of searching, you can use a slow analogue ramp to scan the tuning, or you can do it digitally within a PLL (Phase Locked Loop) - where the software would sequentially increase the frequency in the correct steps.

 

[Roff]

Do a Google search for "Direct Digital Synthesis".

 

[andrew8485]

Thank you all for replying now i can do more research with the info you gave me. these are the reasons why message boards are just as important as search engines thanks

 

[andrew8485]

i just got around to looking these topics up and it apears that i need to use programing to do this. does any one have a scamatic of a nice radio. there is accually not alot of tutorials on the web thanks