KX1, ATU, and output power

[w1pns]

Hi folks,

Should the ATU affect output power from the KX1? If not, here's my
conundrum:

After finishing the 80-30 mod, the power output seemed a bit low. As per
the instructions, I adjusted turn spacing on one of the two toroids on
the new filter board and achieved 4 watts out on 80m and 30m, and 3
watts out on 40 and 20 at 14 vdc.

I reinstalled the ATU, buttoned up the case. With the radio running into
a 50-ohm dummy load, and with ATU engaged, I got about 1.5 watts on 80m,
around 3 watts on 40m, 4 watts on 30m, and about 2.5 on 20m. These
readings came from the internal watt meter, as well as an outboard
NorCal wattmeter.

I opened the case again, pulled the ATU, tweaked winding spacing, left
the ATU out of the package, and the power levels returned to the
original 4/3/4/3. I plugged the ATU back in and the same reduction in
power out resulted.

On inspecting the boards, it didn't look as though the ATU was
physically impinging on the new filter board. And with the ATU attached,
but with both boards out of the case, I was able to tweak windings to
get the 4/3/4/3 output again...until the boards went back into the case.
Then it was back to 1.5/3/4/2.5ish.

What could be altering the output? The only thing I could think of was
that the toroids might be wound a bit tight, so that when tweaking the
spacing between windings, the windings basically slide back into more or
less the original positions in about the time it takes to close the
case. Yeah, it's a reach, but it's all I've got at the moment.

Any thoughts/suggestions? I can try operating without the ATU and use my
outboard tuner. But I figured as long as I've got the tuner, I'd like to
use it.

With best regards,

Pete

--
Peter N. Spotts -- W1PNS
http://www.w1pns.net
Email: [hidden email] | Skype: pspotts
QCWA #34679 | SKCC #4853T | QRP-ARCI #4174
NEQRP #714 | NAQCC #2446 | GQRP #13202

"Amateur radio is a contact sport.
Get on the air and make a contact!"
        -- Lyle Amundson, K0LFV
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[Don Wilhelm-4]

Pete,

Any tuner will have losses, but they should be minimal, yours are drastic.

Are you evaluating the power output with the ATU in CAL mode? -- it
should be
Are the powers you reported working into a dummy load? -- it should be.

If those two conditions are met, I suspect that you have some problem
because the L and C components should be bypassed by the relays.  I
would look for a problem in the relays (usually a soldering problem).

If you are getting those results by tuning into an antenna, then I would
suspect the antenna and conclude that the KXAT1 is not capable of tuning
into the range of impedance presented by the antenna.
The KXAT1 is optimized to use the antenna depicted on page 10 of the
KXAT1 manual (and that does not include 80 meters)

73,
Don W3FPR

On 7/24/2013 8:14 PM, Peter N. Spotts wrote:

> Hi folks,
>
> Should the ATU affect output power from the KX1? If not, here's my
> conundrum:
>
> After finishing the 80-30 mod, the power output seemed a bit low. As
> per the instructions, I adjusted turn spacing on one of the two
> toroids on the new filter board and achieved 4 watts out on 80m and
> 30m, and 3 watts out on 40 and 20 at 14 vdc.
>
> I reinstalled the ATU, buttoned up the case. With the radio running
> into a 50-ohm dummy load, and with ATU engaged, I got about 1.5 watts
> on 80m, around 3 watts on 40m, 4 watts on 30m, and about 2.5 on 20m.
> These readings came from the internal watt meter, as well as an
> outboard NorCal wattmeter.
>
> I opened the case again, pulled the ATU, tweaked winding spacing, left
> the ATU out of the package, and the power levels returned to the
> original 4/3/4/3. I plugged the ATU back in and the same reduction in
> power out resulted.
>
> On inspecting the boards, it didn't look as though the ATU was
> physically impinging on the new filter board. And with the ATU
> attached, but with both boards out of the case, I was able to tweak
> windings to get the 4/3/4/3 output again...until the boards went back
> into the case. Then it was back to 1.5/3/4/2.5ish.
>
> What could be altering the output? The only thing I could think of was
> that the toroids might be wound a bit tight, so that when tweaking the
> spacing between windings, the windings basically slide back into more
> or less the original positions in about the time it takes to close the
> case. Yeah, it's a reach, but it's all I've got at the moment.
>
> Any thoughts/suggestions? I can try operating without the ATU and use
> my outboard tuner. But I figured as long as I've got the tuner, I'd
> like to use it.
>
> With best regards,
>
> Pete
>

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