[Elecraft] Audio Drive and transverter

[Ron D'Eau Claire]

I have suspected that my HC-4 microphone element is not driving the K2
hard enough, but have never had a good way of testing it. I have made
many SSB contacts and VOX sort of works.....We switched to 10m to verify
that the K2 was working. There the report was week but good audio. I am
wandering if my audio drive is too week to put enough power out of the
K2 to reliably key the transporter. Is this reasonable?.
Jeff Burns
AD9T

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It's easy to tell if your mic is putting out enough audio, Jeff.,
without anything but the K2 itself. 

First, transmit into a dummy load with the POWER control set at 10 watts
and switch the meter to ALC mode (press/hold the DISPLAY) button. In ALC
mode the bargraph reads right to left. Transmit in SSB and watch for the
right bar to flicker. On 10 meters it might flicker just a bit. But as
long as one bar is flickering occasionally, that means that you have all
the audio gain you can use. The flicker means that the K2 is
automatically reducing the audio gain to keep the r-f output down to 10
watts PEP. If you reduce the POWER and transmit, you will see more bars
flicker as the ALC must cut the audio gain more to hold the PEP Power
output down to the level set by the POWER control.

On some other bands, such as 40 meters, you will usually see two or
three bars flicker with the POWER control set to 10 watts. That's
because the r-f gain of the transmitter is higher on that band, meaning
that the K2 must reduce the audio more to hold the output level to 10
watts. 

You can switch back to "RF" mode (press and hold the DISPLAY button) and
transmit again. Now the r-f output meter is acting as a "peak" reading
power meter. When you set the power to 10 watts, the bar to the far
right should just flicker on some voice peaks, meaning that the peak
envelope power (PEP) is just touching 10 watts. 

If you are not getting the full power, or if at least one bar of the ALC
display is not lighting when you transmit, then you have low audio gain
for some reason. If everything else is okay, perhaps a preamp will help.
But the MH1 was chosen as a mic to provide adequate gain for the K2, so
I'd look carefully at other possible causes first. 

One obvious thing to check is the SSBA setting on the MENU. It should be
set to 2 or 3. If it is set to 1, it will attenuate the microphone input
by 10 dB. That should only be used if you have a very high level audio
source that tends to "over drive" the K2. 

Ron AC7AC
K2 # 1289