Need help with adapting AM/FM radios

[kimbear]

I would like to adapt standard AM/FM radios with a circuit that sweeps the radio thru either the AM or FM band (Depending on if the radio is in the AM or FM mode). The speed of the sweep needs to be adjustable, and needs to be able to be added to most solid state radios.
Whatcha think??

I have the attatched schematic, (not from me)

but I dont know what to think of it.

 

[Nigel Goodwin]

It would need to be an electronically tuned AM/FM radio (with varactor diodes), most just use multi-pole variable capacitors.

 

[gophert]

Why not buy one? Sweep/seek is a common feature on modern radios.

 

[kimbear]

Can Variactors replace the Varicap?

 

[kimbear]

Why not buy one? Sweep/seek is a common feature on modern radios.

I do noit want it to stop at stations

 

[gophert]

I do noit want it to stop at stations

Then add some masking tape to keep the seek button pressed.

 

[kimbear]

I would like to be able to be added to units that have a Variable capacitor tuning. Maybe someone can help me with adding variactor tuning to Capacitor tuned circuits??

 

[audioguru]

Every radio will use different variable capacitor values.
You must design a circuit to match the existing variable capacitors (most radios has 3 variable capacitors per band).
You must disconnect and remove the existing variable capacitors to add your varactor circuit.
Why sweep the tuning?

 

[kimbear]

May we chat in private Uncle Scrooge.
I may be mistaken, as I so usually am, but most radios seem to have the standard dual , or center tapped Variable capacitor. Once I find a radio that works, I will probably use the same model of radio

 

[Ylli]

Trying to build a "Spirit Box"?

 

[kimbear]

You bet your furry ass YLLi

 

[audioguru]

Instead of your impossible "reolace the variable capacitors with varactors" idea, it would be more suitable to design and order new parts for a varactor tuned radio. A lot of work.