KX1 Sidetone?

[Richard Todd Perry]

I've got my KX-1 board construction complete through Part II, and am working
the Part II checks.

A few questions -

First, the sidetone level is VERY low. When the AF Gain is at the 12 o'clock
position as per the manual, I can't hear the sidetone on any of the three
levels. With the level at three, and taking the AF Gain knob to the upper
"stop" results in some background noise with a _barely_ audible sidetone
using the code speed menu to generate the tones (about a "2" or "3" signal
against the noise, if I was listening to it on the air.)

I'm a little confused, too - I thought side tones were generated through the
transmitter section (I'm not the hottest guy in the world for radio design,
but I seem to remember that it normally comes from the BFO?) - the point is
that I don't have any of that stuff installed yet. Does the sidetone in the
KX-1 get generated in U1, perhaps? I thought that perhaps that the level
would improve when I peaked the receiver trimmer caps (since the manual says
that sidetone level is set in relation to the normal received audio), but
that didn't help. The AF level with the gain cranked up isn't what I'd call
overwhelming, either (but it's not weak, either.)

Now, as a related thing, I was cruising the archives and noticed that not
all earbuds are created the same (which shouldn't surprise me, I guess.) Can
anyone suggest a good model and online source for use with the KX1? I'm
currently using a set of the "flat disc"  waterproof-style Sonys (that's
what I had on hand). No idea of the sensitivity.

And finally, I've had ongoing problems with U1 seating. Part I worked great,
but the first time I turned the unit on for Part II, I only had about half
of the LED lines working. A few troubleshooting minutes later, I pushed U1
into it's socket a touch further and have had no problems since (or maybe I
have?) I guess my question about U1 is this - the pins on U1 measure roughly
3/64 from the surface of the socket to the "shoulder" - is this "seated far
as possible"? Or do I need to push harder?

IF the sidetone is generated in U1, and IF U1 isn't seated far enough, these
problems might be related.

I should add that all resistance, voltage and solder checks are normal. I
checked that the ATU jumper was OK, too. The only other unusual things that
I've seen so far is a little noise in the headphone jack when moved
(unsurprising) and all three pots having a little noise when moved (however,
resistance checks are normal.) I thought that I would go back and
doublecheck the physical position of everything in Part II tonight, but
since this is the only problem, I'm not thinking I'll turn up anything
(famous last words!)

Can you all help? I'm thinking that (either) something in the sidetone
generation process is screwed up, or that something in the AF amplifier
circut is.

Oh, and finally - can I use the Elecraft noise generator to peak the bands?
I've been using an antenna wire, since I wasn't sure if the noise generator
was a large enough signal to activate the AGC or not, but the noise
generator would be a lot more convienient and repeatable.

I know the above is a lot to answer, but before I really get this thing torn
apart for troubleshooting, I thought I'd check to see what actual problems I
had, first!

72 DE V7/KF4BAL

Richard Perry


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