[Elecraft] KX3 Faulty SWR indication

[Peter Lambert]

The funny SWR also appears with the ATU in circuit but not at the tuning PWR level.  It appears when the rig is in "normal" transmit mode after tuning.  Bob is likely right though - try turning the power down and see if results in "normal" operation.  You may find it power dependent - if so it could be very hard to fix unless you're experienced and willing to solder and unsolder parts.

73's Peter VK4JD

-----Original Message-----
From: elecraft-bounces at mailman.qth.net [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Bob McGraw K4TAX
Sent: Wednesday, 31 January 2018 11:38 AM
To: elecraft at mailman.qth.net
Subject: Re: [Elecraft] KX3 Faulty SWR indication

Based on your description, I'd say there is some instability in one of the stages.   The dummy load will present a uniform impedance at all frequencies, thus the SWR will be 1:1.   output network will show evidence of reflected power.   Using the ATU, it adds filtering thus eliminating the spurious output.    I suggest looking at the output on a spectrum analyzer.

73

Bob, K4TAX


On 1/30/2018 7:09 PM, Dave Sublette wrote:
> A few weeks ago I posted this problem, worked on it a bit, then got 
> distracted into other projects.  I am now back trying to resolve the 
> faulty SWR issue with My KX3.  The problem only occurs on 160, 80 and 60 meters.
>
> Using a known good dummy load and cable the indicated SWR on the KX3 
> is high --- 1.8 to one using 10 watts.  An external wattmeter/SWR 
> meter shows the Dummy Load as a perfect load.  The reflected power needle does not move.
>
> I have done repeated Power Out Calibrations with the KXPA100 (not 
> relevant, I know).  The KX3 shows the same faulty SWR Readings with or 
> without the KXPA100.  Of course the ATU mode is in bypass.  But, when 
> the ATU is active, it matches, shows a proper SWR briefly, then shows 
> the faulty reading as the rig transmits.
>
> It was a factory built unit S/N 4932.
>
> I'm stumped.  I guess it is time to send it home for healing.
>
> Dave, K4TO
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