[sdiy] voltage-controlled AM radio tuning

[Simon Brouwer]

Scott Gravenhorst schreef:
> A note about the AM (American band) radio: I used to play with crystal
> sets as a kid
> and it was quite standard that the variable capacitor for tuning the
> circuit was a
> 365 pF job.  That's a little big for varactors, but as been said they can
> be paralleled.

The ones in cheap transistor radios have much smaller values, around 150
pF. The section for the oscillator is even smaller.

See for example items BC-540 and BC-88 on
http://www.oselectronics.com/ose_p98.htm

5 BB153 varicaps (ca. 0.2 EUR in small quantities) in parallel give at
least 173 pF.

-- 
Vriendelijke groet,

Simon Brouwer
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