[hpsdr] Cyclops 1st LO VCO

[John Miles]

It all comes down to how much complexity you want in the design.  You should
be able to reach HP 8566-level phase noise performance with those Synergy
parts that Chris mentioned, and for many people who want a spectrum
analyzer, that will be good enough.  I wish the Synergy VCOs were more
widely-distributed!

An optimal design would use several good VCOs to cover the required octave,
but that gets very complicated, very quickly.  Spurs are likely to be a
problem if you don't make arrangements to power down the VCO(s) that are
unused at any given time, and of course the loop-filter tweaking process is
more laborious as well.

-- john, KE5FX

> -----Original Message-----
> From: hpsdr-bounces at lists.hpsdr.org
> [mailto:hpsdr-bounces at lists.hpsdr.org]On Behalf Of Lyle Johnson
> Sent: Wednesday, May 07, 2008 5:46 AM
> To: richardh at iinet.net.au
> Cc: chris at chris-bartram.co.uk; n0tvj at atmc.net;
> grant at ghengineering.co.uk; hpsdr at lists.hpsdr.org
> Subject: Re: [hpsdr] Cyclops 1st LO VCO
>
>
> ***** High Performance Software Defined Radio Discussion List *****
>
> > Thinking about this - I presume the first LO has to cover 1000
> - 2000 MHz
> > Not too many VCOs will do this...
>
> Not sure where this all fits in the scheme of Cyclops, but in general
> you do not want to use a VCO with a wide range.  For example, in the K3
> th VCO covers a range from 8 to 44 MHz.  But it does so in 64
> overlapping "bands".  This is necessary to keep phase noise manageable.
>
> For example, if a 10V swing moved your VCO 1 GHz, then 1 uV will move it
> 1 kHz...
>
> 73,
>
> Lyle KK7P
>


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