The tuning sensitivity kv is 2.4 times the of the receiver VCO. This means the loop filter in the synthesizer will not be at optimum. I have therefore decided to reduce the tuning sensitivity to a closer match to receiver VCO. The modification I have done to reduce the tuning range is to replace the vari-cap diode with a pair BB833 in parallel to give a change of capacitance of ~11pF for a 4V change. The results of the change are shown in the graph on the right and the data below.

66.6MHz @ 1V
73.6MHz @ 5V
Tuning sensitivity 1.75MHz/V

Reduced Tuning Range

Milled Prototype PCB