[Elecraft] RE: new rev B K2 build: low sensitivity

[Sverre Holm - LA3ZA]

I took a look at your measured values from some days ago. You said:

"Checked AF amp -- sidetone level 255, no speaker or headphones
connected, 
voltage at speaker connector is 0.56VAC. At setting 128, it's 0.29VAC."

Compare that to my measurements from quite some time ago below. It seems
as yours are too low. On the other hand, what could possibly be wrong
with such a simple circuit as the LM380 AF amplifier, except possibly,
the coupling capacitors?


73
Sverre
LA3ZA


Reply-To: <la3za at qsl.net>
From: "Sverre Holm - LA3ZA" <svholm2 at online.no>
Date: Sun, 30 Dec 2001 19:02:38 +0100
Subject: [Elecraft] K2: more headphone output

I have done some measurements and experiments with a smaller value for
the headphone series resistors. I paralleled the two 82 ohms resistors
with 22 ohms each. I then adjusted my 600 Hz sidetone level for 100 mV
rms before the resistors, on my multimeter, in my K2 this is St L = 056.
I have done the sidetone modification, so my sidetone is close to
sinusoidal.