[Milsurplus] BC-221-AK frequency spread question

[WA5CAB at cs.com]

One guess would be that the effective or stray shunt capacitance across the 
circuits is higher than it was 60 years ago.  I don't think that the components 
you are looking at were supposed to be painted with MFP varnish but if 
someone did it, that could be your problem.  I've had BC-611-F's that were heavily 
coated with varnish where I had to use the next higher range antenna coil in 
order to get them to tune up.

In a message dated 12/28/2008 10:41:53 AM Central Standard Time, 
olegerityincj at austin.rr.com writes: 
> Finished rebuilding the Master oscillator re-checking Coils, Capacitors 
> and Resistor values. Replaced 3 of 4 resistors which were way out of 
> spec.  One resistor was still dead nuts 5K. Replaced resistors 14, 
> 15,19. All the CAPS were with in 5% tolerance.  Both the Low and High 
> band coils were within 5% of specified value on the schematic.  After 
> replacing the components, another story, the band spread out a bit but 
> not quite back the original positions with in range of the Corrector.  I 
> can get the top end in but the lower end of the band is off a bit, not 
> with in correctable range of the Corrector. 
> Low Coil spec 7.06 mH measured 7.00 mH
> High Coil spec 25.84uH measured 26.2uH
> 
> 
> Any ideas on what causing the band coverage to narrow? 
> Any ideas on getting the band with in the range of the corrector cap?
> 
> I am going to remove the MO coils and re-check again the corrector plate 
> distances.
> 

Robert Downs - Houston
wa5cab dot com (Web Store)
MVPA 9480
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