[hpsdr] More on Horton LO

[Chuck Clark]

Synergy has a 900-2200 VCO with about -99 dBc 10k offset phase noise.  
This gives you an octave plus tuning range.  They have also announced a 
new series with better phase noise, -110-120 10 k phase noise, 250-1000 MHz.

Worries about noise on the tuning line may be a little over rated in a 
PLL.  Inside the loop bandwidth spurious will be supressed by the loop 
gain, to the level of the multiplied reference oscillator.  As a normal 
rule there will be a large cap at the tuning port of the VCO to filter 
higher frequency components on the tune line.  Normal RF practice would 
attempt to isolate the PLL, reference or DDS from other noise in the 
system using shields, line filters and deadicated regulators.  We should 
probably plan for it from the begining.

Now a question, if the clock for a DDS has jitter(phase noise) how can 
the output not have jitter?  I think if we use a DDS we will want the 
highest possible 500 MHz multiplied crystal to get the cleanest signal.  
I don't have data but I think the higher frequency clock results in 
lower spurs.   Comments
Chuck
AF8Z