[Elecraft] ALC indication on K2

Sun Dec 7 22:57:08 2003

The amount of ALC you see is a function of the gain of the RF circuits =
in
the transmit path as well as the amount of audio being delivered to the
balanced modulator. A "decent" amount of ALC is when a single bar lights =
on
voice peaks when you have the POWER control set for full output and the
compression set to whatever level you like. That indicates that you are
reaching the peak output power set by the POWER control. Any more bars
simply indicates that the ALC is turning the gain down farther. It =
doesn't
help the signal in any way.=20

Normally, the K2's RF circuits have the least gain on 10 meters, but the =
way
the output circuits shared between 80 and 160 are designed can result in
lower-than-normal transmitter path signal levels there too.=20

The first question to answer is whether the K2 makes full RF output in =
CW
mode (10 watts if a K2 or 100 watts for a K2/100) into a suitable dummy
load. If not, then you need to  troubleshoot the transmitter signal path =
to
find out why it's low.=20

If the CW power reaches spec then take a  close look at how the ALC =
behaves
as you reduce the POWER setting.=20

First, be sure you have SSBA set to 2 or 3. SSBA 1 attenuates the mic =
input
about 10 dB.=20

Next, see how close to full output you are. If you start to see ALC on =
160
as you drop the POWER control slightly below maximum (say, down to 9 =
watts
instead of 10 for a K2 or 90 instead of 100 watts for a K2/100) then you
have ALMOST all the gain you need. It's probably too close to care =
about.
But if you have to drop the POWER level too far, then you probably need =
a
little more audio into the mic jack. (The K2 RF indication on the =
bar-graph
is a "peak reading" output meter, so you can see directly how much power =
you
are getting by watching it too).=20

Increasing the audio level from your microphone is the usual way to =
increase
the RF signal path by getting more out of the balanced modulator. That =
works
FB as long as you don't use so much extra amplification in the mic that =
you
over-drive the audio or balanced modulator.=20

One easy mod to get more audio without changing mics or adding an =
external
mic pre-amplifier is to change R14 on the SSB board. The "stock" value =
is
1k. Raising it to about 6K ohms will provide substantial additional gain
with most mics.=20

Beyond that, look at the builder's resources on the Elecraft WEB page,
particularly the mods developed by John Grebenkemper. He has one that
provides much greater TX gain without distortion.=20

Ron AC7AC

-----Original Message-----

My K2 does not give me any ALC indication when I am on 160. It is decent =
on
75 and 40 and week on the other bands.

The Rig seems to operate just fine with the exception I am still =
tweaking
the VOX. It has a Elecraft MH2 (Heil) mike.

Any thoughts?

73,

Rich

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