[ARC5] Subject: Re: Easy selectivity improvement.

[J. Forster]

If you have an old RF signal generator it is relatively easy to add a
'wobulator' - a small speaker turned into an audio frequency driven
variable capacitor- to turn it into a narrow range sweeper.

These days, adding a variacap to an RF generator is nearly trivial, All
you need is a back-biased signal diode as a varicap (or a real one... 
they are cheap), a coupling cap, and a couple of resistors and an source
of sweep waveform.

It'd be a trivial retrofit for some kit-built RF generators.

-John

===============



> There is a specific sweeper circuit for viewing IF curves on a scope was
>  called a "Wobbulator"  the British vintage radio magazine "Radio Bygones'
> No. 82 April/May 2003"   featured a updated advanced model - If you search
> for it - you will find a copy of it on the net.
>
> A UK glowbug that goes by the moniker "AndyDaviesByTheSea" on You Tube has
> a nice demonstration of the unit in action - he credit the
> units usefulness in one of video in getting a grossly misaligned
> Eddystone
> communications receiver  back on track.   Try Videos   44- 48
>
>
> Fred Cousins
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