[Elecraft] Issues with K2 Align & Test

[Don Wilhelm]

Ron,

Yes, your BFO is out of range.  It may be that your BFO crystals are a 
bit higher than they should be.  You could ask Elecraft for a 
replacement or you can pad your crystals down a bit with capacitors.

There are two ways to pad the BFO - the first is to add capacitors in 
parallel with C173 and C174 - try adding 47 pf to C174 and 120 pf to 
C173 (other value combinations are possible, but try to keep the ratio 
of the two values in the 1:2.6 range).

The second way to pad the frequency down is to add a small value 
capacitor from the junction of the crystals and C174 to ground.  Do not 
exceed 20 pf if you use this method.

The broadband signal may just be the effect of the BFO being off 
frequency.  Wait until the BFO is correct before making any further 
judgments.

73,
Don W3FPR

Ron Hahn wrote:
> Colleagues,
> 
> I've just finished the receiver section of my K2 and have run into some 
> issues with alignment and test (part 2)..
> 

> 
> BFO Hi : 4917.62 >= 4916.3
> BFO Lo : 4913.59 <= 4912.7 !!!
> Range  : 4.03    >= 3.6kHz
> 
> All BFO components checked and confirmed to be correct..
> BFO coil checked for shorts against resistor retainer..
> 
> Now, the problems...
> 
> 1.  The BFO Lo is out of range;  This appears to have a knock on effect 
> with the filter cal.  I've checked all the component values and also 
> rechecked the 4MHz osc calibration, and can't get the BFO within range. 
> What could possibly be wrong? Built-in frequency counter seems to be 
> accurate when measuring an external reference.
> 
> 2.  There is a constant broad-band S5 signal on the S-meter, and this 
> can be confirmed by plugging in the headphones.  ALC works normally. 
> Injecting a signal into the aerial input is masked by the internal 
> signal (wherever its coming from).  Changing filter settings has some 
> impact on the signal strength. This says to me that something is 
> oscillating that shouldn't be??
>