[Elecraft] Re: KAT100 LEDs Overactive on Reflected SWR

[James Brown]

Gentlemen:

I am having a strange problem with my KAT100, similar to that stated by
Mario, but with a twist -- it only occurs on 20m and only with my Gap Titan
antenna, and only on highpower SSB, and only when using the KAT100 with the
K2. The LEDs bounce with voice peaks up to #5, resulting in Hi Refl error.
It appears as if the K2 goes into oscillation until I unkey the MH2; the
power supply indicates a steady 18 amps. If I unkey and rekey within a
second or so, it returns to a locked condition. If I let a few seconds
elapse before rekeying, everything is again normal.

If I drive the Gap directly from the K2, everything is fine, as it is with
my TS-530S and Collins S-Line.

The tuner drives 88' doublet via a RadioWorks Remote Balun and ladder line,
and an end-fed135' wire at full power with a near 1:1 match on all bands
with no problems. It matches the Gap at 1:1 on all bands.

Station is properly grounded.

Troubleshooting steps taken to no avail:

-Updated firmware to 1.04.
-Replaced all station jumpers with commercial RG-8X jumpers.
-Inserted RadioWorks T-4 line isolator between tuner and K2.
-Installed large split-core chokes on Y-cable between tuner and K2, and
between K2 and computer.
-Installed large split-core choke on MH2 cable. Also tested with an MC-50
mic.
-Disconnected VRFDET line at K2 end of cable.
-Verified calibration of tuner. It is in close agreement with an Autek WM1
computing watt meter.
-Hurled non-repeatable epithats at the tuner.

Any ideas, help, or condolences greatly appreciated.

Thanks,
Jim Brown, K5JAZ

-----------Original Message-------------
Date: Mon, 20 Jan 2003 17:47:06 -0800
From: Wayne Burdick <n6kr@elecraft.com>
Organization: Elecraft
To: Mario Lorenz <ml@vdazone.org>
Cc: elecraft@mailman.qth.net
Subject: Re: [Elecraft] Re: KAT100 LEDs Overactive on Reflected SWR

Mario,

If you see unwarranted high peak-SWR readings, and they are not dealt with
by
the new revision of KAT100 firmware (1.04), then they almost always indicate
high RF on the VRFDET line and/or a spontaneous mismatch condition of some
kind.
There are a number of suggestions in the back of the KAT100 manual, to which
I
would add those you mentioned here.

Thanks,
Wayne
N6KR


Mario Lorenz wrote:
>
> Am 19. Jan 2003, um 22:49:13 schrieb Wayne Burdick:
> > Hi Roy,
> >
> > KAT100 f/w revision 1.04 (the latest) does a lot more averaging, and
should
> > eliminate this problem. If it doesn't, please let me know.
>
> Wayne, I can confirm this problem happening with 1.04 as well. Sometimes
> thats up right into the red LEDs. I push tune, the tuner matches SWR down
> to 1.2:1 or so, and while I talk on SSB (80m in this case) the LEDs
> illuminate, in some cases up to the reds.
>
> I think the issue is twofold.
>
> 1. correct allignment. I've found the dummy loads to be critical. I have 3
> dummy loads, all supposedly 50 Ohms, with different power ratings. All of
them
> requiring slight adjustments to the trimmer to zero the bridge. Depending
> uppon which dummy load I used for alignment, the effect is better or
worse.
>
> 2. Stray RF. I seem to have such problems, I have seen the K2 loose
contact
> with the KAT100 (ATU vanishing, Ant A/B switch going Not-Inst, until
> power-cycle). The latter went away after applying proper grounding to
> both the K2 and the EC2 with the KAT and the KPA (I run the KPA in the EC2
> together with the KAT)....

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