Thanks Said, My object of the exercise was to multiply the error of a 10Mhz Rb /GPSDO source so that I would get 8x phase error between two compared frequencies. This I presume would make adjustments of my sources much easier.
OTOH, if we lock 80Mhz to Rb source and use that as a clock for the Super DDS 2 VFO kit, then I would have a pretty good HF signal source. http://www.pongrance.com/super-dds.html Cheers Raj, vu2zap > >Hello Raj, > >our ULN-1100 and ULN-2550 GPSDO's use a 100MHz VCXO locked to the 10MHz >OCXO via an ADF4002 PLL with less than 40Hz bandwidth. After careful >optimization of the layout and the loop filter, the phase noise results are >quite >excellent at 100MHz, see the attached plot. The plot shows two versions of >the PLL loop filter from the design phase of the products, one has been more >optimized. You can see that the noise floor is almost -170dBc/Hz at 100MHz. > >You get the best of two worlds: the absolute frequency accuracy of the >GPSDO, and the very low phase noise of the VCXO above the PLL bandwidth. It is > >clearly visible that the VCXO phase noise inside the loop bandwidth is >actually also reduced by locking it to the 10MHz OCXO (the PN curve below the >loop bandwidth frequency of ~30Hz would just continue going up without the >PLL) > >Low Noise 100MHz VCXO's are readily available at mouser and digikey (so >are 80MHz units), and programming the ADF4002 is straight forward with the >help from the AD online tools. It can be bit-banged with any microcontroller. > >bye, >Said > > >I was contemplating the same thing. I fed the output to a bifilar >transformer and >diode doubler and got good results. I have to add an amp and double it >again twice >more. It is still on breadboard. The object was to multiply the error 8x >and compare. > >Probably a PLL locking to 80 Mhz will retain the long term accuracy of the >TBolt reference. > >Raj, vu2zap > _______________________________________________ time-nuts mailing list -- [email protected] To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts and follow the instructions there.
