[Elecraft] P3 - Wandering Baseline ... SOLUTION, I think

[Fred Jensen]

I complained recently about my P3 baseline occasionally wandering 
upward, sometimes on one side, sometimes on the other, and sometimes all 
across, in a sort of "humpish" [an engineering term] fashion.  I took it 
off-list because it was intermittent, unpredictable, and things I might 
try in response to suggestions usually had no effect because "the 
effect" went away as soon as I did anything, like even got near it.

Thanks to Gary at E'cft Supt, I think I may have found the problem and 
fixed it.  If you are about to build a P3, please read:

Like most things Elecraft, the case is in several parts, and you sort of 
build the "chassis/case" around the electronic guts [another engineering 
term] as you assemble it all.  Square areas around the screw holes for 
the case parts will have been masked off and not painted, and the 
E'folks are light years ahead on this from when I built my K2 ... my P3 
parts looked positively sterile.  I checked continuity for several of 
the shiny spots, and they were dead-to-ground.

Don't believe your eyes.  While DC continuity might be there, RF may 
not.  I removed and burnished [as the instructions had suggested when I 
built it] each of those spots.  I reassembled with loose screws, and 
noted the same problem ... baseline humpish [engineering term again], 
hand on top stops it [an engineering diagnostic, sometimes followed by a 
sharp "tap"].  Now, when I tighten down the screws, problem gone.

So, no matter how bright and shiny they look, follow the instructions 
and clean all of them, and when you're ready, make the screws tight. 
Doesn't take long, worth the effort, easier than removing all of them 
afterwards.

For the real engineers in the crowd [my degree is in math]:  I don't 
think this was related to "normal". RFI.  Being a mathematician and not 
a real engineer, I currently have no idea what it really is related to, 
but "clean case mounts = clean display."

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2011 Cal QSO Party 1-2 Oct 2011
- www.cqp.org