[Elecraft] KXPA100 not making antenna connection

Wed Sep 3 19:37:30 EDT 2014

Josh,

     Looking at the owner's manual, page 41, there is a simplified 
schematic. In theory, if the unit is in "bypass," it should be a direct 
"in" to "out" connection. There could still be some other 
considerations, but I would suspect that's the way it is. Until someone 
from Elecraft says otherwise or someone with a working unit can measure 
theirs to disprove of prove the idea, I would operate under that 
assumption. You might also want to give the good folks at Elecraft a 
call about your problem. Maybe it has a very simple solution.

     Hope you get it operational soon!


     kurtt WB9FMC
     2015 Hamfesters Hamfest Chairman
     Looking for my replacement since 2014!
     http:\\ham-ham.org

On 9/3/2014 16:41, Josh Lehan wrote:
> On 09/03/2014 03:17 AM, Kurt Pawlikowski wrote:
>> Josh,
>>
>>      Unfortunately, I'm not familiar enough with the KXPA100 to know if,
>> when  bypassing the unit internally, there is DC continuity between the
>> input and output. If there is (I suspect so), you should be able to
>> measure between them with a regular ohm meter. While not 100%
>> definitive, if it fails this test (again, assuming DC continuity), that
>> would be a major indicator of some connection problem.
> Good advice.  I used a multimeter to measure for continuity.  Yikes, the
> tip and the ring of my "RX IN" jack appear to be shorted to each other,
> and also shorted to ground!  Is that normal?
>
> I'm going to open it up and check the wires carefully on the panel where
> the jacks are, hopefully nothing is touching.
>
> I've heard that measuring antenna stuff at DC can be an illusion, as
> some things are supposed to appear open or appear shorted at DC, as
> they're designed to carry RF, not DC.  My meter can only measure
> resistance at DC, it can't do anything fancier (no capacitance or
> inductance, no measuring resistance at AC/RF, no impedance or reactance).
>
> Also, when the antenna is selected, the tip and the ring of "ANT 1" (or
> "ANT 2" if selected) also appear to be shorted to each other and to
> ground.  The KXPA100 isolates the antenna that is *not* selected: its
> ring is still shorted to ground, but its tip has no connection.
>
> Josh
> K6JSH
>
>
>>      Hope that helps!
>>
>>
>>      kurtt WB9FMC
>>      2015 Hamfesters Hamfest Chairman
>>      Looking for my replacement since 2014!
>>      http:\\ham-ham.org
>>
>> On 9/3/2014 03:24, Josh Lehan wrote:
>>> Hi there!
>>>
>>> I assembled my KXPA100 (with ATU) recently, serial number 0595.
>>> Unfortunately, it isn't working.  The link to the KX3 works great
>>> (rather slick, everything was instantly recognized), but the KXPA100 is
>>> not making any antenna connection cleanly.  KX3 is properly configured
>>> to link with the KXPA100.
>>>
>>> I heard nothing at all, on any band, as if the antenna wasn't connected
>>> at all.  I tried initiating an ATU tuning cycle, only to see a SWR fault
>>> on the KXPA100 almost instantly, so I stopped that rather quickly.  The
>>> SWR wouldn't improve below 32.0-1 (terrible).
>>>
>>> I opened it up again and removed then reconnected the tricky little TMP
>>> connectors, and that helped a little.  Using needlenose pliers made all
>>> the difference.  I am now pretty confident I have the TMP connectors
>>> fully inserted (they weren't, earlier).  Now, I can hear stations very
>>> faintly, S0 at most (not enough to light up any signal bars on the KX3).
>>>    This is still very bad, because when bypassing the KXPA100 by using a
>>> barrel connector to connect the KX3 to the antenna directly (for
>>> testing), it's loud and clear, around S5-S9, which is normal for my
>>> antenna.
>>>
>>> I can transmit just fine, using the KX3 and its built-in ATU, without
>>> the KXPA100, so I can rule out anything else in my setup that might be
>>> causing a problem.  Both antenna and dummy load normally work great.
>>> Ruled out cables by using barrel connector to join two cables together
>>> directly (cutting the KXPA100 out of the circuit) and that also worked
>>> great.  I just can't get a good connection when going through the
>>> KXPA100.
>>>
>>> Now, I'm at a loss what to do.  I think there might be a fault with the
>>> ATU connection internally of the KXPA100.  It was straightforward to put
>>> it together, though, I don't think I made any mistakes there, but
>>> probably will disassemble it all and try again.
>>>
>>> Switching between antenna 1 and antenna 2 makes an audible difference in
>>> the noise level, so I know that works.  However, the ATU switch on the
>>> KXPA100 doesn't seem to make a difference at all, there is no difference
>>> in noise level between bypass/manual/auto.  Shouldn't there be an
>>> audible difference here?  There also is no difference when KXPA100 is
>>> powered off vs. on, which seems strange to me.  Same SWR fault happens
>>> instantly when trying to tune with ATU, or doing any transmission for
>>> that matter.
>>>
>>> What should be my next step in troubleshooting?
>>>
>>> Thanks!
>>>
>>> Josh
>>> K6JSH
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>>
>