[Elecraft] K2 output @2W

[Don Wilhelm]

Steve,

If you are seeing an oscillation of the power output level, you might try
reducing the ALC loop gain.

One can increase the value of R98 on the RF Board to decrease the gain
through the K2 power determining ALC loop.  If the value is increased too
much, the power output on 10 meters will be reduced, so some experimentation
is in order.

Increasing R98 is a step sometimes taken when the KPA100 is installed to
decrease the 'power hunting' cycle (my terminology), but I have never seen
the base K2 need such treatment (the KPA100 adds more gain inside the loop
and the loop overshoots).  Be aware that this is a condition where the power
output varies with a longer keydown (or TUNE) time.  If your actual problem
is confined to a mismatch between the power requested and the actual power
output, then the answer to that problem may be different - in that case,
look for something that may cause the load to vary, or something like a bad
solder connection in the K2 output detector and its path back to the
microprocessor.  In my experience, the base K2's power determination is
quite stable.  If the KAT2 or KAT100 is involved, the wattmeter section of
those parts may be providing incorrect data to the K2 microprocessor and
cause such behavior.

73,
Don W3FPR

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net]On Behalf Of Leigh L Klotz, Jr.
> Sent: Saturday, February 04, 2006 12:51 PM
> To: Larry Phipps; w3fpr at arrl.net
> Cc: Elecraft; Steve Hostetler
> Subject: Re: [Elecraft] K2 output @2W
>
>
> The HFPacker amp has a 3dB pad on the input so you might need to take
> that into account.  I use mine with a KAT100 on the output and an
> internal KAT2.  I disconnected the Vrfdet on the KAT100 cable as it has
> the amp in the gain loop, and the K2 software only knows about the
> KPA100.  With the KAT100 enabled, the KAT2 is put into passthrough
> mode.
>
> The K2 power control seems about the same for me with the amp in or out
> -- 1.7 gets 1.5, and 2.0 gets 2.5, and there is no choice between, as
> measured by the KAT2 internal Vrfdet.
>
> Leigh / WA5ZNU
> On Sat, 4 Feb 2006 8:40 am, Larry Phipps wrote:
> >
> > Along these lines, you can isolate the K2 from the amp by putting a pad
> > between them. You can then run the K2 in a more linear range, and
> > guarantee a good load at all times. I would try 6 dB. Of course,
> > efficiency will suffer.
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