[Elecraft] K3 - background hiss (noisy K3) - update

[dmb at lightstream.net]

Hello Bozidar,

I suspect that the issue may be particular to your particular K3. You did
not mention the S/N range of your radio, and I may be incorrect about this
but I think that very early K3's had an issue similar to this, that was
quickly resolved.

The S/N of my K3 is in the 58XX range, and I have never heard any of the
hiss that you describe. I have a pair of Grado SR225e headphones that have
an impedance of 32 ohms, and are very sensitive. I plugged them into the
Phones jack on the front of the K3, and with the AF gain control turned
fully CCW, there is no hiss or for that matter any sound at all.

It's possible that there is an issue with your AF Gain control/encoder.
You might want to use the built-in test that allows you to check the
encoder steps of the two AF gain and two RF gain controls that is
available from the CONFIG > SW TEST menu on the radio. This requires that
you first make sure that "Tech Mode" is enabled. To do so, go to CONFIG >
TECH MD and then turn your VFO-A dial so that "On" shows above TECH MD on
your K3. Then, rotate your VFO-B dial to navigate over to the "SW TEST"
menu option. Then slowly rotate your AF Gain control on the K3. You should
see the encoder steps (visible on your K3 display) increasing in number as
you rotate it clockwise, and decreasing in number as you rotate it CCW. In
my case, rotating the AF Gain control fully CCW shows a step of 2. If your
value is higher than that at fully CCW, perhaps your AF Gain encoder has a
problem.

73,

Dale, WA8SRA


> Hi,
> i have studied all the posts about this topic.
> Seems, that is still, huge confusion about that, so i will try to
> formulate
> a problem on simply way:
>
> *With low impedance earphones plugged into the audio jack on the K3, you
> can
> hear a really annoying noise (hiss) even with the AF and RF volume set to
> zero(CCW). This audio hiss has a constant level, is added to the audible
> RF
> noise and can prevent one from hearing weak  signals on an otherwise quiet
> band.*
>
> That hiss has nothing to do with K3 receiver or settings - simply is
> permanent present.
> This indicate that something must be wrong with earphones amplifier
> LM4811MM, and that is
> odd, because LM4811MM seems to be an high quality chip, designed exactly
> to
> work with low impedance earphones , with a minimal amount of external
> components?
> My question is:
> is, in the mean time, known any hardware (or anything else) modification
> for
> that issue?
>
> best regards,
> Bozidar
>