K2: HI Power OUT during Tuning with an external ATU: normal?

[VK7JB]

Hello Group,

K2 #6998 is now singing. The calibration and alignment went very smoothly. I
feel very pleased with myself :)  I've built the KSB2, KDSP2 and KNB2 to go into
this rig, but it's currently still a base K2 while I learn to drive it.

I have noticed something odd about the power while tuning using an external
autotuner and I'm wondering if it this is normal:

Set up:
Base K2
13.5V power supply
LDG z11 pro 11 auto ATU

Running the K2 into my DL1 50ohm dummy load, all works perfectly.  Expected
power out on all bands as measured by a voltmeter attached to the DL1 and on my
Autek WM1. No problems, until I connect the autotuner.

On 80, 40 and 30m when I hit "TUNE", the LDG autotuner starts and completes a
tuning cycle and indicates a 1:1.0 match, confirmed on the Autek meter.  But,
regardless of what power I request on the K2 prior to tuning, as the tuning
cycle starts, I get a Hi Cur warning as current draw rises to between 3-4A for a
power out of 12-15W measured on the Autek.  Power and current draw stay High,
despite the 1:1 match, until I hit TUNE and exit TUNE mode.  Then, if I
transmit, or hit tune again with a match already set, the power reduces to  or
what is dialed in to the K2 power setting and all is OK until I change bands and
hit TUNE to initiate another tuning cycle.  This occurs with the LDG tuner and
my Elecraft T1 tuner.  But again, operating into the dummy load, all works
perfectly - the power you dial in is what you get, on any band.

It's seems as if the reactive load presented to the K2 prior to the tuning cycle
is causing the K2 to ramp up the power out and current draw and the K2 stays in
this high output state until TUNE mode is interrupted.

Hope this makes sense.  

So can anyone tell me if this is expected behaviour when using an external
autotuner with the K2?  The fact that all works as expected into a dummy load
makes me think the problem's not with the rig.

And a second question - is it OK to leave the frequency counter permanently
connected inside the rig to TP2 so you can adjust the BFO/Filter settings on the
fly?

Thanks in advance for any advice and 73,

John
VK7JB




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[Geoffrey Mackenzie-Kennedy]

Hello John,

Here I use a 40m dipole at 70 ft fed with open wire line and a homebrewed
remote antenna tuner as a reference antenna system, and I have not seen any
sign of the problems that you have described when using my K2 barefoot, nor
with the KPA100 in line, on any of the HF bands. But I should add that this
tuner requires less than 1 watt to adjust itself.

To confirm or otherwise that a reactive load is the cause of your problem, I
suggest that a useful test would be to TUNE using a dummy load ( 50 +j0
ohms) with a suitable value of capacitance in shunt right at the dummy load.
The voltage rating of the capacitor must be adequate of course, but an open
ended stub of coax whose length is roughly between 1/8 to 1/4 wavelength X
coax's velocity factor at the test frequency could be used in lieu of a
discrete capacitor.

With regard to a permanent frequency counter connection, based on a lot of
work that I did to remove my K2/100's receiver "birdie" problem I would not
do this. However our operating habits might differ, birdies drive me daft
:-)

If I do not reply immediately to any further thoghts you might have, please
bear with me because I will away - as I have been for some time.

73,

Geoff
GM4ESD


John, on Saturday, October 16, 2010 at 13:28 + 0100 you wrote:

> Hello Group,
>
> K2 #6998 is now singing. The calibration and alignment went very smoothly.
> I
> feel very pleased with myself :)  I've built the KSB2, KDSP2 and KNB2 to
> go into
> this rig, but it's currently still a base K2 while I learn to drive it.
>
> I have noticed something odd about the power while tuning using an
> external
> autotuner and I'm wondering if it this is normal:

<snip>

> It's seems as if the reactive load presented to the K2 prior to the tuning
> cycle
> is causing the K2 to ramp up the power out and current draw and the K2
> stays in
> this high output state until TUNE mode is interrupted.
>
> Hope this makes sense.
>
> So can anyone tell me if this is expected behaviour when using an external
> autotuner with the K2?  The fact that all works as expected into a dummy
> load
> makes me think the problem's not with the rig.

> And a second question - is it OK to leave the frequency counter
> permanently
> connected inside the rig to TP2 so you can adjust the BFO/Filter settings
> on the
> fly?


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