Editing Variable-frequency oscillator (section)

{{Short description|Oscillator whose frequency can be tuned over some range}}
{{Redirect|VFO}}
[[File:Heathkit DX-60B HG-10B 090403.JPG|thumb|upright=1.5|A Heathkit [[amateur radio]] transmitter ''circa'' 1969, with external VFO]]

A '''variable frequency oscillator''' ('''VFO''') in [[electronics]] is an [[oscillator]] whose [[frequency]] can be tuned (i.e., varied) over some range.<ref name="arrlhandbook">{{cite book |title=The ARRL Handbook for Radio Amateurs, Sixty-Eighth Edition |editor=Larry D. Wolfgang |year=1991 |publisher=American Radio Relay League |location=Newington, Connecticut |isbn=0-87259-168-9 |pages=Chapter 10 |no-pp=true }}</ref> It is a necessary component in any tunable [[radio]] transmitter and in receivers that work by the [[superheterodyne]] principle. The oscillator controls the [[radio frequency|frequency]] to which the apparatus is tuned.