[Heathkit] Mohican BFO question, other things.

[Edward B Richards]

Phil;

The RF tuning should have prominent peaks. Is the correct transistor in
the RF amp stage ?

73, Ed Richards K6UUZ


On Sat, 22 Jan 2005 02:33:48 -0000 "Philip Atchley"
<beaconeer at sbcglobal.net> writes:
> Hi,
> 
> In working on this Mohican and going through it thoroughly I've 
> found an 
> anomaly in the BFO circuit (varactor tuned).
> 
> 1.  The schematic (BAMA download) shows resistor R91, 1.5K between 
> the 
> low side of the Pot and ground.  On this set the low side of the Pot 
> 
> goes directly to ground, no R91.  Was this a design change or did 
> somebody do it themselves, perhaps to get additional BFO range?  The 
> 
> problem I have with it is this allows the Varactor to have "Zero" 
> bias 
> on it, and it could then act as a "rectifier" of the generated 
> signal 
> Voltage, instead of a capacitor as it's supposed to be.  It just 
> doesn't 
> seem "right".
> 
> 2.  The tuning of the antenna coils/trimmers, antenna tune control 
> seems 
> to have very little response.  The RF amplifier is now working after 
> 
> replacing it's RF amplifier, but the tuning is non critical/almost 
> non 
> existent.  Is this a very "Low Q" circuit and just not responsive or 
> 
> should I be looking for a problem component/wiring?
> 
> 73 de Phil,  KO6BB
> 991 Different NDB's heard to date.
> 
> http://www.geocities.com/ko6bb/
> Merced, Central California, 37.3N  120.48W  CM97sh 
> 
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