[Elecraft] KI6WX modes for the KSB2 ?

[John Grebenkemper, KI6WX]

Jeff;


> I have been reading over KI6WX modes for the KSB2 and have a few questions
> before I jump in.
>
> First the simple one. I have a whole box of parts marked "2N2222". Are
these
> equivalent to the PN2222? If not, what is the difference? It would be nice
> to know for future reference.

The PN2222 is a plastic case version of the 2N2222.  I'd be a little
reluctant to use the metal case version because the collector is tied to the
metal case and might short to a nearby part.  The PN2222A/2N2222A has
slightly better breakdown voltages and can be used as a substitute.  I
believe Radio Shack still carries the PN2222.
>
> Now the more difficult question. I have a Heil HC4 microphone element, and
> changed R2 to get more drive. Everything works now, including VOX, but I
> suspect that a little more drive would be beneficial.
>
> As I read John's notes the "KSB2 Increased Gain Modification" is
appropriate
> for my microphone, but I should leave R2 as I have it and skip the "KSB2
> Reduced Intermodulation Distortion Modification." Is this correct? Would
it
> be better to do the "KSB2 Reduced Intermodulation Distortion Modification"
> and add a pre-amp to my microphone if the drive is insufficient? I have
had
> the parts for a pre-amp in an envelope for almost 2 years.

This is a more difficult question to answer.  Reducing R2 increases the
audio gain of the KSB2, but makes it more likely you will drive the NE602
input into clipping, especially if you set SSBC greater than 1-1.  With a
low gain microphone, I would do the following.  Add the increased gain mod
and put the 2.2K resistor across R1 (this resistor reduces your dependency
on the input impedance of the NE602 to set the audio gain).  If there isn't
enough audio gain to get to a full 10 watts on 10 meters in SSBC 1-1, I
would then decrease R2 until I can get enough output.  I wouldn't reduce R2
below 2K unless you avoid running SSBC above 1-1; audio compression will
create really strong audio clipping with compression enabled at this audio
gain level.  An audio preamp on the mic input would be even a better
solution.

-John
 KI6WX
>
>
>
> Jeff Burns
>
> AD9T
>