Hi,
As others have already noted, there's a paucity of circuits or down to earth advice on this topic - unless your poison is "millimetre wave" technology. I set out to GPS-lock my Icom 706 transceiver some while ago. This uses a (single) hi-stability master 30MHz xtal oscillator. With support from Murray (ZL1BPU), I decided to IL rather than generate an external GPS-locked 30MHz source. The only reference other than that by Uzunoglu to IL oscillator design I managed to find was in Jessop, 4th Ed, 1994 (p9.50) which stated: P1/P2 = [2Q*deltaF/F]^2 where: P1 = pwr of injected signal P2 = Oscillator (to be controlled) power Q = loaded Q of cavity (ie: xtal osc) F = oscillator frequency delta F = locking range Working the formula backwards together with lab testing confirmed that the greater the injection level, the greater the lock-in range and vice-versa. In practice, I coupled a +10dBm 10MHz square wave via a ~15dB attenuator into the 30MHz xtal osc's "pulling inductor" via a 2 turn loop. This allowed the IC-706 to lock-up within 10" of turning on from cold and then remain in lock. Theory suggests that lock sensitivity could be improved in this instance if the 10MHz duty cycle was changed from 1:1 to 6 or 7:1, the idea being that the narrower pulse should be <0.5 period of the frequency of the oscillator to be locked. I didn't pursue this avenue as the additional stray GPSDO 10MHz signal present within the Icom didn't interfere too greatly with WWV reception on 10MHz. Spectran's display, however, showed another story. Measuring the lock BW with varying injection levels was an interesting exercise ! On a related topic, I found some while ago - and promptly lost - a graph/chart showing harmonic level variations with varying duty-cycle of an input waveform. This was to some degree a graphical representation of the Wenzel document referenced by Bruce recently. Has anyone got a link to this document please ? Kit VK2LL ------------------------------------------------------- > Joop, > > you may also search for "synchronous oscillator". You will find for > example: > > http://www.amalgamate2000.com/radio-hobbies/radio/synchronous_oscillat > or.htm > > Best regards > Ulrich > >> Are there references to some practical circuits? That would be great. >>snip >> Cheers, >> Joop >> -- _______________________________________________ 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.
