[Elecraft] KPA100/KAT100 on 160 Hi Current

[Don Wilhelm]

John, Julius,

The normal thing to look at in a high current situation is the low pass
filter.  Check both on the base K2 and the KPA100.  First thing is to count
the turns on the toroids - count only the turns that pass through the center
of the core or you might end up with an extra turn.

On the 160 meter band, one extra turn is all it takes to create a high
current situation because the cutoff frequency of the LPF moves down into
the 160 meter band and shunts some of the signal to ground.

The KAP100 LPF is easy to sweep with an antenna analyzer - connect the
ribbon cable to the K2 and select the band of interest, put a 50 ohm
resistor into the input cable and attach the analyzer to the SO-239.  If you
do not find a low SWR throughout the band, the LPF is to blame.

73,
Don W3FPR

> -----Original Message-----
> From: elecraft-bounces at mailman.qth.net
> [mailto:elecraft-bounces at mailman.qth.net]On Behalf Of John Reiser
> Sent: Thursday, December 07, 2006 10:43 AM
> To: J F; Elecraft Discussion List
> Subject: Re: [Elecraft] KPA100/KAT100 on 160 Hi Current
>
>
> Hi Julius,
>
> Both my K2/100s, #4970 and #5570 exhibit excessive current draw on 160
> meters, as indicated by the ammeter on my 30 watt Astron PS.  It
> gets up to
> 27 or 28 amps.  I use a 30 amp fuse.  In every other respect, my two
> K2/100's work perfectly.  Current draw on all the other bands is
> less than
> 20 amps.
>
> I don't have an antenna for 160, so I never transmit on that band anyway,
> and this is not a big problem for me.  Still, being a bit of a
> perfectionist, it bothers me that it exists.
>
> I mentioned it on the reflector a while ago.  Someone said they
> had the same
> experience, but had no solution.  Someone else suggested that I
> retune the
> 80 meter bandpass filter to represent a compromise between 80 and 160.  I
> tried that, but the excessive current draw continued regardless of the
> bandpass tuning.  (Could it be due to the KPA100 going into
> oscillation at
> the 160 frequency?)
>
> When I saw your post, I became hopeful that it might evoke a
> response from
> someone who had come up with the definitive solution.  But so far there
> hasn't been any.
>
> Good luck and 73,
>
> John, W2GW
>
> ----- Original Message -----
> From: "J F" <phriendly1 at yahoo.com>
> To: "Elecraft Discussion List" <elecraft at mailman.qth.net>
> Sent: Wednesday, December 06, 2006 5:49 AM
> Subject: [Elecraft] KPA100/KAT100 on 160 Hi Current
>
>
> > Well ARRL 160 is history now.
> >
> > As usual, with the K2 I heard more than I could get to
> > hear me ;o) Evidently I heard and worked more than
> > some of the local contesters with "other" brand
> > equipment heheh.
> >
> > Anyway I have a problem... I use the KPA100 with the
> > KAT100, and there may be no connection between the
> > two, to stretch the bandwith of my antenna. If I set
> > the K2 for 100 watts (or just twist the knob far
> > clockwise), the ALC does not kick in. In a key down
> > situation, the current keeps climbing until the fuse
> > blows. If I set it for 99 watts (I realize this is not
> > that precise) the ALC does function somewhat. I've not
> > tried it with a dummy load. The antenna was fairly
> > well matched (1.2:1 at it best point)and has a current
> > balun on it. So this really shouldn't be happening. Do
> > I have a problem with the KPA?
> >
> > Thanks,
> >
> > Julius
> > n2wn
> >
> >
> >
> >
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