[hpsdr] GIBRALTAR LO generation question

[CT1IZU]

> Speaking of the AD995x... I see where Giuliano I0CG
> <http://it.geocities.com/giulianoi0cg/ad9951.html> used a 500 MHz
> source with his AD9951 that was derived from a 100 MHz oscillator with
> the 5th harmonic filtered by a Toko helical resonator filter.  The
> helical filters are expensive.

I wonder if you specified this too tight. Most people use the the cheaper
5HW/7HT types in this sort of application. These are around 3-4 pounds
sterling( around 2 bucks) in singles and as low as 2.64 on 100 off. G4HGT
used the 252MX-1549A to filter a 100MHz Butler osc for 405MHz out for 432
transverter. DB6NT shows similar circuits for 2.4GHz using 5HW types.
Assuming a clean osc we are talking about removing a component 100MHz away.


 I wonder if you could get the same
> results with a 80 MHz oscillator's 5th harmonic filtered by a ECS SAW
> filter at 400 MHz?  The SAW filter has a bw of 80 kHz centered on 400
> MHz and cost about $4.  This would drive the AD9958 at 400 MHz would
> still should be good up to 160 MHz or so.

A variation may be a  VCO  based on 180 deg phase shift SAW. Some info was
in TT (RADCOM) September 1995. Design was attributed to Di Paolo Franco of
Ericsson Fatme Rome.

Shel CT1IZU



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