[Elecraft] K2 freq stability

[Don Wilhelm]

LS,

That is not usually a problem if the rubber mounting stem has been cut 
off as instructed and the 1/8 watt resistor is pushed down inside the 
toroid core (so the core cannot move).

One does not usually manipulate the bottom cover during operation, so 
the only time the BFO is liable to shift is when pressure is placed on 
the bottom cover.
That is not 'drift' IMHO, but a change because of the physical proximity 
of the bottom cover.

73,
Don W3FPR

On 4/24/2016 9:31 AM, lstavenhagen wrote:
> Hi all,
> Here's an interesting finding, though I apologize if this is already in the
> past archives.
>
> No matter how careful you are when installing L33 on the bottom of the
> board, it's so close to the bottom cover that any movement of it, say when
> you're picking up the rig or manipulating the bale, etc., will pull the BFO.
> On my 2nd K2 that I just completed it was so bad that I could pick up the
> rig, set it back down and the tone of signals was very slightly, but
> noticeably off.
>
> So what I did was put a lockwasher between the cover and the standoff near
> L33 to raise the cover a little bit and get it the heck away from L33 as
> much as I could. It actually made a large improvement in the general
> frequency stability of the rig - which means before I was seeing more
> contributions in overall drift from the BFO in addition to the rest of the
> circuitry.
>
> The washer is an ugly fix, since the cover bows out a little bit, but it's
> totally non-destructive and reversible. I did the same fix to my other K2
> which didn't have the problem to the same degree, but it helped on that one
> too.
>
> Fortunately the slightly bowed out bottom cover is under the rig and you
> never see it. But just in case you've been experiencing more drift in your
> K2 than you think you should get, or it pulls when you pick it up.... that's
> a fix that is working on mine.
>
>