[Elecraft] Re: New Problem after Stability Mod

[Wayne Burdick]

Jim,

Let's take these one at a time.

BFO: The resolution (increments) possible in setting the BFO vary a bit, but 20
Hz is pretty typical. Because of this, there's no guarantee that you'll be able
to hit 4916.30 exactly. Getting to anywhere within 10 to 20 Hz of your target is
more than adequate since the narrowest filter bandwidth you can get from K2
filtering is 4 to 5 times that.

PLL: If you have an instability in the PLL, the first thing to check is the
value of R19, which you no doubt soldered on the bottom of the board (it isn't
present on the rev A RF board). Unfortunately some early BFO mod kits were sent
out with 220 ohm resistors for R19, and this value turned out to be too small.
This was the subject of a recent builder alert. The value should be between 1.8
and 3.3 k. It is 2.7 k in the Rev B K2.

Let me know if this helps.

73,
Wayne
N6KR



Jim G wrote:
> 
> Installed the PLL/BFO kit to my K2 (s/n 2105 with Rev A board).  When I
> began re-entering the BFO settings I noticed that the last digit would
> jump around; for example, if my BFO setting was 4916.30, it would jump
> from .29 to .31.  I was not able to set it exactly on .30.  I've also
> noticed that I have a frequency instability that shows up every 5 Khz
> when tuning.
> 
> Reading the Rev B PDF indicates that this is a PLL instabilty problem.
> However, I notice this problem every 5 Khz across the entire 40 meter
> band.  It's also showing up on 20 meters.
> 
> Any ideas on what I should be looking for?
> 
> Thanks-
> 
> Jim
> K4GT
> 
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