Re: Ozark Patrol problem


W0PWE
 

Ed,
On mine the switch is to the left for the higher frequency band. When switched to the right the 560pf capacitor is added in to the oscillator circuit and the lower band should be selected.

I put my scope on the Q1 collector and did some checking. On the high band it could easily be made to oscillate by turning the regen control. I measured the oscillator at roughly 4.6MHz to 13.5MHz at extremes of the tuning capacitor. 

When I switched to the low band however I could not make it oscillate anywhere in the band with any regen pot setting. I then pulled the 560pf capacitor (C11) and checked it with my AADE meter. It looked good (543pf). So then I tried various capacitors in place of C11. Various combinations of mono ceramic capacitors I had on hand all supported oscillation. Even up to about 700pf it oscillated without trouble. I'm not sure what it is about that 560pf disc ceramic but the oscillator doesn't seem to like it. Low Q maybe? 

My current combination of odd capacitors in C11 measures 526pf and the ends of the dial will oscillate at 3.4 and 4.6 MHz. If you have a different capacitor that you could try in C11 it might be worth a shot. Good Luck.
73 - Jerry

Join main@4SQRP.groups.io to automatically receive all group messages.