[hpsdr] Cyclops Front end questions

[richardh at iinet.net.au]

OK - I have a weekend to start on this
Some questions for the gurus:

(1) Input circuitry
I note the SSA at 
http://www.scottyspectrumanalyzer.com/msaslim.html#Mixer_1_using

just uses DC connection to the input mixer
Should we have attenuators here?
What about AC vs DC coupling/limiting/matching pad etc?

(2) 1st Mixer
We seem to have settled on the ADE-11X +7dBm device - any better ideas?
What about associated circuitry?

(3) 1st LO
Several candidates for the VCO 

Minicircuits ROS - 2150VW as has been used in SSA
+5V supply +4dBm  out Phase noise at 10KHz -96 dBc/Hz Range 975 - 2150 MHz
Cost $29.95 in 5
Stocked Minicircuits ?anywhere else

Crystek CVCO55CW - 1000 - 2000 
+10V supply +5.5dBm  out Phase noise at 10KHz -100 dBc/Hz Range 1000 - 2000 MHz
Cost $30.00
Stocked Mouser - not Digikey

Synergy Microwave "YIG replacement" DCYS100200-12
+12V supply +4dBm  out Phase noise at 10KHz -105 dBc/Hz Range 1000 - 2000 MHz
Cost ? - anyone know?
Stocked ?

I guess we will have to use a buffer to bring the outputs up to +7dBm
?Which

(4) PLL 
All the previous circuits have used the National LMX2326
Is there a better alternative?
I note that the SSA uses a IC regulator with minimal filtering after it to supply 
the reference for the loop filter opamp - these have a fair bit of low frequency 
noise - we used a zener/pass transistor for our supplies in the microwave synth a 
few years ago. 
What sort of noise floor can we expect from the loop filter?
We would aim to have 2MHz steps so the reference shouldnt be an issue.
The loop filter needs a higher voltage supply than Atlas currently provides - could 
we put say 24V on the Atlas bus? A switch mode regulator wouldnt be great on the 
Cyclops board

(5) Roofing filter
I am proposing a Toko 4 pole 6DFC-1030C-10 dielectric filter as in the Cyclops wiki.
Would this be sufficient?

(6) What about all the losses through this setup - do we need some gain?
will be in the order of 13-15dB so far with the same again in the second mixer/SAW 
filter.

(7) Where are all the signals for the tracking Generator derived?
I am still a bit vague on this.

I await soem responses

Thanks
Richard VK6BRO