[time-nuts] sub harmonic VCO locking

[glen english LIST]

Before I commit the soldering iron, can anyone share their sub-harmonic 
injection locking experiences ?

I have to make 393.216 from 49.152 .
Yes, lots of ways.... I know.

injection locked at 1/8 of the frequency from the decent source.

There wont be any issue of locking to the wrong harmonic, the VCO will 
be on the money.I was thinking of using a dielectric loaded TEM 
resonator  or TEM coax line VCO .

and why do this : ?
- I need all the non related spurs to be > 115dB down.

- a double-double-double could work, but my experience is for x2 x2 x2 I 
really need to filter well at each stage to avoid sum and difference 
products.. which might be OK for this application , especially if I 
filter really well after the first x2 . but avoid if I can. filters at 
908 MHz need space, and shield cans where it is going.

- and I dont know too much about phase noise and SRD or varactor 
multipliers. but maybe that's an option.

- my attempts at generating low phase noise x6 with class C multipliers 
has been dismal.

- onboard VCO chip/PLLs have all sorts of unrelated spurs in the output.

- sure I can use a good PLL and a external VCO, but if my N value is 
fixed, and I can use injection locking, why bother with the PLL chip 
that is likely to introduce PD related spurs anyway.

regards

glen