Don Wilhelm-4 wrote
> Yes, those two mods are old, and apply only to the A level boards (below
> SN 3000).
> There have been improvements in the K2 sidetone incorporated into the B
> level boards, and are also included with the A to B mod kit.
> The changes added a 47k resistor in series with C24 (R11 for the B level
> boards) and a shielded 82mH inductor across pins 7 and 10 of RP5.
> The sidetone is still not a pure sine wave, but it is close if your
> sidetone pitch is between 500 and 700 Hz.
>
> Those old mods would be applicable to unmodified A level boards but
> re-design of the circuits would be required for the B level boards and A
> level boards already modified with the A to B upgrade kit.
Don I beg to differ. From LA3ZA's K2 mod site:
########################################
Sidetone mod
Updated Nov 2006
Even more sinusoidal tone than the mod in serial #3000+ gives
Important to have an inductor with correct series resistance (KT5X)
Simple, one more capacitor
TF3MA
############################################
I installed this mod in my S/N 4119 and it made a huge difference in
sidetone quality. The original design had so much harmonic content that it
was difficult to zero beat stations by ear.
73, Bill W4ZV
--
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http://elecraft.365791.n2.nabble.com/latest-K2-serial-tp7615395p7615492.html
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