[Elecraft] 2 meter amp for K3 or KX3

[Joel Hallas]

The problem with most 2 meter "brick" type amplifiers, is that while they
may have an "SSB" switch position, it generally only changes the TR
switching method, and doesn't make them linear. The only medium-power 2 M
amp I found that was linear, while we were testing them for QST was the
Tokyo Hy-Power 300 W amp, that was in a whole different price category from
the bricks, until they discontinued it.

While transmit linearity may not be a big deal for casual operation, the
consequences of transmit IMD for other folks in busy areas during a VHF
contest (about the only time people around here are on 2 M SSB) can be as
severe as on the HF bands. Since I couldn't seem to generate any interest
from Eric and Wayne in offering a suitable amplifier, I commissioned Jim
Klitzing, W6PQL to come up with a lower power version of his excellent 2
meter kilowatt that he published in QST. He did, and you can read about it
in:

May 2013 - QST (Pg. 30)
Build a Linear 2 Meter 80 W All Mode Amplifier

It can put out 100 W on CW, 80 W on SSB, with HF like IMD. It is fairly
simple because it is based on a single amplifier module, and costs less to
build than a brick. For this application, you can eliminate the automatic
switching circuitry, although it doesn't take much, and then can be used
with your FM handheld. It doesn't include a preamp because the K3 has a
better NF than most preamps.

It can operate at almost any input level (including that of the KX3 2 meter
mod, I believe) by setting the input attenuator. Because its current drain
is less than the K3 during 100 W transmit, it can be run from the same power
supply, since the K3 HF PA is off when on 2 meters. I have one and have been
very happy with it. I believe Jim offers various parts kits on his website.

You do have to remember to switch it off when you go to 6 meters, since the
amp quiescent current is high enough when the PTT switches to pop the PS
breaker with 100 W on 6. You learn quickly.   
 

Regards, Joel Hallas, W1ZR
Westport, CT


Subject: [Elecraft] Suggestions for a 2 meter amp?
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I installed the internal 2 meter module in my K3 so now I'm in the
market for a good Amplifier to bring it up to at least 100 watts.

The K3 puts out 10 watts so the amp needs to be 10 Watts input

Any Suggestions?