Australian Amateur Radio Station
|For anyone doing Microwave portable operations, frequency accuracy is very important to success. Many
operators these days have taken advantage of PLL circuits and various synthesiser packages.
Most of my transverters run "free running" Local Oscillator schemes usually as OCXO's and I thought the
idea of having a GPS locked MARKER GENERATOR for quick frequency checking in the field would give me
the "best of both worlds". ( A well designed free running LO cannot be beaten for signal purity!) I am very
happy with the stability of my LO's and thought that I could utilise Graham's Synthesiser as a marker
generator to allow me to be certain of my frequency calibration whilst out portable.
For use like this, I built Graham's board into a small box and placed wire links to the on board switch for
frequency selection on the front panel. A 10 MHz GPS controlled signal is fed into the unit from a seperate
portable unit and by "dialling up" the correct frequncy I can hear a signal all the way to 24 GHz with a short
wire on the SMA output socket in close proximity to my transverter whilst operating portable. Now I don't
need to guess where ***.100 is anymore!
I have also tried one of these synthesiser boards in my 10 GHz terrestrial unit and can not hear any
difference when listening to a weak signal. BUT when listening to a strong signal there is definite
issues with PLL synthesiser noise manifesting itself with very loud sidebands out to +/- 40 KHz. . I would
hate to think what a transmitted signal would sound like and would suggest that anyone utilising them as
part of an LO chain in a transverter would check very closely for the synthesiser noise.
I would like to stress that as a test instrument or a marker generator, they are
.......Thanks Graham ( VK3XDK) for doing the hard work on these and making them available.
I think Graham is still selling these boards (as well as some excellent transverter module kits). Try contacting him directly
if you are interested.
|(Implementation of the VK3XDK Synthesiser)