UHF VCO circuit

[Peter Bolch]

Hi,

I'm looking for a low phase noise and low distortion VCO circuit for
frequencies from about 500 MHz to 1GHz. A tuning range of 1:1.5 is enough.

To improve phase noise I thought of using several varicaps in parallel and
so a
circuit with only one variable capacitor would suit me best.

Thanks

Peter

[John Miles]

Very hard to justify hand-building something like this, considering the
great prices on the Mini-Circuits VCO line. Check out
http://www.minicircuits.com/98dg161.pdf for some examples.

-- jm KE5FX

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[JohnsonHE]

>
>> Peter
>
>Very hard to justify hand-building something like this, considering the
>great prices on the Mini-Circuits VCO line. Check out
>http://www.minicircuits.com/98dg161.pdf for some examples.
>
>-- jm KE5FX
>
>

Low phase noise they are not!

W4ZCB

[John Miles]

Lower than anything you're going to build by hand with random hunks of
metal as a resonator, though.

If he is talking about a cavity oscillator, of course, he can do a lot
better. But the 1.5:1 tuning range pretty much rules that out. (Even
the MC VCOs on that page don't have that wide a tuning range, although
they sell others that do.)

[Pushpendra Singh]

Dr Ulrich Rohdes new BOOKs
Microwave and Wireless Synthesizers theory and design isbn
0-471-52019-5
and
Communications Receivers 2nd Ed

has what you want + actual circuits with component values.

[Hugh Duff]

Don't forget to use molded RF chokes around the oscillator circuit to
help reduce the noise generated by resistors.

Hugh Duff VA3TO