Project #6  A narrow bandwidth 10 MHz PLL

From the TV synchronised 1 MHz PLL, the idea was to have a higher frequency PLL to enable locking a 100 MHz free running VCO.

The 10 MHz TCXO came available as a surplus unit from the Corver Radio-museum in Budel Noord Brabant NL.

This RS920001 source manufactured by RADIOSYSTEM SWEDEN AB was used as a reference oscillator for UHF base-stations.

The intention is to multiply this frequency to 100 MHz to enable locking various Xtal oscillators of microwave LO’s by mixing them down to a lower more manageable frequency.

Operation is straight forward, the 10 MHz oscillator is divided down with use of the HEF4750 by 640 to 15625 Hz.

The reference frequency comes from the 1 MHz derived 15625 Hz of my ZDF locked source level converted by a HEF4104.

The PI filter around the OP27 opamp is the PLL’s loop-filter. Due to the limited tuning range of the TCXO, the time constant of the loop-filter is rather large and so the bandwidth of the PLL is small.