[Elecraft] KSB2 in K2/100

[John, KI6WX]

I know this message is a bit old, but I've been too tied up with other 
projects to read the reflector mail for the last two months (fyi - the 
reflector generated over 2000 emails in the last 2 months).

The increased gain mod I did for the KSB2 was originally designed to 
increase the transmit gain in SSB for a barefoot K2.  The original K2 had 
difficulty reaching 10 watts of power output in SSB on 10 meters.  When you 
drove the audio input harder to get to full power, the K2 would start to 
clip on the audio peaks.  This does not create a wider bandwidth signal 
because the SSB modulator is followed by the SSB filter, but it does 
increase the audio distortion.  I added the extra emitter follower stage to 
increase the overall IF gain in the SSB transmit signal path.

This mod should not be necessary with the KPA100, since it can reach full 
power with only a few watts of drive.  Some folks have reported that the 
emitter follower stage can cause power output instability when the KPA100 is 
installed.  There is at least one fix around that reduces the gain of the 
emitter follower stage by increasing the emitter resistor value and 
apparently eliminates this instability.  I would recommend that the emitter 
follower gain stage not be used in a K2/100 since it does appear to cause a 
stability problem, and there is no need for the extra gain on 10 meters.

-John
 KI6WX

----- Original Message ----- 
From: "Roy Morris" <w4wfb at carolina.rr.com>
Sent: Saturday, June 03, 2006 9:41 AM


I would like to hear from anyone who has K2/100s with both the unmodified 
KSB2 and the modified KSB2 with the KI6WX 2N2222 amp mod (and 1.08 
firmware).  How does this mod affect mic gain and VOX operation?  How does 
the absence of this mod affect mic gain and VOX operation?  Does the mod 
help SSB modulation on 10 meters with the power level set at 5 watts?  Do 
you find this mod helpful at 100 watts?  Thanks for your input.  Roy Morris 
W4WFB