Sync devices locked to AM broadcast carrier.

These devices provide a common, synchronous clock signal.  This signal can be very handy when two stations  experiment in digital or frequency hopping modes.

The reference is derived from the carrier of an AM broadcast transmitter.  In this case we use BTRN Wereldomroep; at 540 KHZ.  The signal is very strong in Belgium and moreover, the carrier frequency of 540 KHz is just right to PLL lock a 27 MHz crystal oscillator  ( 27000 / 50 = 540 ).

Experiments with one device in Brussels and another in Gent have shown that the two devices stay perfectly synchronised for long periods of time. 

These experiments were done by day.  At night, when the signals of foreign broadcast stations on nearby  frequencies become stronger,  more severe problems can occur.  To solve this problem better filtering of the incoming signal will be necesarry (eg. using a 540 KHz crystal).