06-07-2015, 02:35 PM
Hi David,
Have you checked to see or hear if the local oscillator is running? If it is running properly it should be heard 1000kc at the low end of the band (530kc) and at 2170kc at the top end. LO frequency= Dial frequency+IF frequency (470kc).
As I mentioned before the larger winding on either coil is critical to the operating frequency of that tuned circuit. On the antenna coil the small winding couples the RF signal from the antenna to the input of the mixer. It isn't very critical, the more turns the more signal applied to the secondary.
On the osc coil the small winding is there to provide feedback to make the LO oscillate. Direction is critical. Number of turns, not enough won't oscillate across entire band. Too many will make the oscillator generate harmonics.
Best I remember about 25turns for either coil should work. Is the IF on frequency?? Use signal generator set at 470kc hooked to the grid cap of the mixer. Peak the IF trimmers.
Terry
Have you checked to see or hear if the local oscillator is running? If it is running properly it should be heard 1000kc at the low end of the band (530kc) and at 2170kc at the top end. LO frequency= Dial frequency+IF frequency (470kc).
As I mentioned before the larger winding on either coil is critical to the operating frequency of that tuned circuit. On the antenna coil the small winding couples the RF signal from the antenna to the input of the mixer. It isn't very critical, the more turns the more signal applied to the secondary.
On the osc coil the small winding is there to provide feedback to make the LO oscillate. Direction is critical. Number of turns, not enough won't oscillate across entire band. Too many will make the oscillator generate harmonics.
Best I remember about 25turns for either coil should work. Is the IF on frequency?? Use signal generator set at 470kc hooked to the grid cap of the mixer. Peak the IF trimmers.
Terry
