KX-1 power output varies

[Barry N1EU]

I've been using a KX-1 with KXAT1 ATU and random wire on 20M.  At various
times I notice anywhere from about 1.9 to 3 watts power output.  In all
cases, the ATU has indicated a low SWR after tuning.  I'm wondering why the
power output varies so much.  Is this due to varying losses in the tuner as
the match varies at different locations?

Thanks & 73,
Barry N1EU
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[Bill K9YEQ]

Simple answer:  Yes.

73,
Bill
K9YEQ


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Barry N1EU


I've been using a KX-1 with KXAT1 ATU and random wire on 20M.  At various
times I notice anywhere from about 1.9 to 3 watts power output.  In all
cases, the ATU has indicated a low SWR after tuning.  I'm wondering why the
power output varies so much.  Is this due to varying losses in the tuner as
the match varies at different locations?

Thanks & 73,
Barry N1EU
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[vk4tux]

The tuner is losing little. The losses are in the feedline with variance of
match.

-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Bill K9YEQ
Sent: Saturday, 25 August 2012 1:05 AM
To: 'elecraft'
Subject: Re: [Elecraft] KX-1 power output varies

Simple answer:  Yes.

73,
Bill
K9YEQ


-----Original Message-----
From: [hidden email]
[mailto:[hidden email]] On Behalf Of Barry N1EU


I've been using a KX-1 with KXAT1 ATU and random wire on 20M.  At various
times I notice anywhere from about 1.9 to 3 watts power output.  In all
cases, the ATU has indicated a low SWR after tuning.  I'm wondering why the
power output varies so much.  Is this due to varying losses in the tuner as
the match varies at different locations?

Thanks & 73,
Barry N1EU
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[Don Wilhelm-4]

Barry,

The losses through a properly assembled tuner are small.  I suggest you
check the power output into a dummy load - I would believe there is a
problem if the power is less than 3 watts with a 13.8 volt power
supply.  Check first with the ATU menu parameter set to CAL, and then
again with the ATU menu set to "tun" - you should obtain close to the
same power.

If you still suspect the KXAT1, remove it and put the jumper on J7
(between pins 1 and 3) and measure the power with an external wattmeter.

Be aware that the KAT1 wattmeter power indication is not always "right
on" (it is not a precision wattmeter, but indicates "in the ballpark"),
it will vary in the indication - you should assume that the actual power
is somewhere between the two values it indicates.
The variation in the readings is typically about 0.3 watts - the range
you are seeing is greater than normal, so be certain your antenna
connections are solid and your coax is good.  If you are using UHF
connectors in your feedline, make certain they are seated properly and
tight.  UHF connectors depend on tightness for good conductivity.  Use a
tool and tighten just a shade more than finger tight.

73,
Don W3FPR

On 8/24/2012 8:01 AM, Barry N1EU wrote:
> I've been using a KX-1 with KXAT1 ATU and random wire on 20M.  At various
> times I notice anywhere from about 1.9 to 3 watts power output.  In all
> cases, the ATU has indicated a low SWR after tuning.  I'm wondering why the
> power output varies so much.  Is this due to varying losses in the tuner as
> the match varies at different locations?
>
>

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[Michael Babineau-2]

It is also worth noting that the power output of the KX1 is quite sensitive to
DC voltage in. If you can give it 12v the power output should be closer to
3 to 4 watts.  It is much more sensitive to this than my K1.

Michael VE3WMB

>From: Barry N1EU <[hidden email]>
>Date: August 24, 2012 8:01:37 AM EDT
>To: elecraft <[hidden email]>
>Subject: [Elecraft] KX-1 power output varies


>I've been using a KX-1 with KXAT1 ATU and random wire on 20M.  At various
>times I notice anywhere from about 1.9 to 3 watts power output.  In all
>cases, the ATU has indicated a low SWR after tuning.  I'm wondering why the
>power output varies so much.  Is this due to varying losses in the tuner as
>the match varies at different locations?

>Thanks & 73,
>Barry N1EU
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[Don Wilhelm-4]

Michael,

The KX1 does not have a power control loop as the K1 (or K2, K3, KX3)
have, so its power output is highly dependent on the voltage. Those with
power control loops measure the output power and report it to the MCU
which will adjust the drive to attempt to produce the requested power.  
If the voltage is low, it will just take more current to produce the
requested power output.  The KX3 is a bit different in that it switches
output impedances at lower voltages (and reduces the power) to remain
more efficient.

73,
Don W3FPR

On 8/27/2012 8:19 PM, Michael Babineau wrote:
> It is also worth noting that the power output of the KX1 is quite sensitive to
> DC voltage in. If you can give it 12v the power output should be closer to
> 3 to 4 watts.  It is much more sensitive to this than my K1.
>
>

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