[Elecraft] Sidetone with harmonics at 400 Hz...

[Ron D'Eau Claire]

The frequency of the sidetone makes a *big* difference in the waveform. 

Also, rather than assume it's as good as it gets, it might be worth taking a
close look at the filter circuit provided. The sidetone is filtered by U10B
on the Control Board and associated components. If something is amiss there,
the filtering might not be as good as it should.

I noticed that Ken K3IU pointed out that there *was* a mod that took place
somewhere around S/N 3000 that did clean up the sidetone a bit more. It'd be
worth looking into that further if you have a pre-S/N3000 K2. I believe that
involved adding a 47k resistor between C24 and RP7 pin 8, changing
electrolytic C33 to 4.7 ufd, and  adding a small 47 mHy choke from RP5 pin 7
to ground. 

Just because some of us aren't so bothered by a little buzz'n and clunk'n
doesn't mean that it must be so ;-) 

Indeed, the grumbling about the K2's sidetone died down so much that I
suspect the mods did a very good job. That sounds to me like it's likely
something not quite right rather than a design deficiency. 

Ron AC7AC

-----Original Message-----
From: elecraft-bounces at mailman.qth.net
[mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Rob Locher W7GH
Sent: Saturday, August 04, 2007 11:59 AM
To: Elecraft Discussion List
Subject: Re: [Elecraft] Sidetone with harmonics at 400 Hz...


Hi Ken,

Thanks for the email.  I've compared the sidetone from my K2 to the sidetone
from several others, and mine is about typical.  I don't doubt that my tone
would look sinusoidal on a scope, since the harmonics are probably several
dB down from the fundamental tone.  However, they are there, they can be
seen on Spectrogram, and they are annoying (to me at least, but not to Ron
AC7AC).  I also have a problem zero-beating with the stock tone, like Steve
N6VL.

The bottom line is that the audio from the SCAF-1 is much nicer, and I think
that many other K2 users would think so also.

73!
- Rob W7GH