K2 XMT Power Meter is Gone

[Curt Milton]

My K2 seems to be working fine -- the KAT100 is working, and it is transmitting
full power.  But there is no power indication on the LED meter, and instead I
get a high current warning even though all is well.  This just turned up today
on 'an old K2.'  It is misbehaving at all power levels - woops I just figured
out the power control does not seem to be working when I am above 'QRP'
settings.  The rig was only moved a few inches since it was last used.  Has
anyone else experienced this ?

73 Curt


     
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[Don Wilhelm-4]

  Curt,

Situation -- lack of proper power control - the K2 transmits a full
power no mater what the power request knob is set to.

I suspect that you left the antenna connected to the K2/100 when not
operating.  A static surge from the antenna (wind, rain, snow, lightning
induced) caused the KPA100 diodes D16 and D17 to be damaged (I would
check the wattmeter diodes on the KAT100 as well).  These diodes are
right at the K2 antenna jack and are critical for the K2 to control its
power level.

The best future cure for this problem is to disconnect the antennas from
the K2 when not operating.  An antenna switch is preferred rather than
physically disconnecting the coax.  PL-259 connectors mate the center
conductor before the shield and if there is a charge on the antenna,
that can damage the diodes when the antenna is connected - a simple
antenna switch solves that problem.

Wind, rain, snow and nearby lightning can produce a significant amount
of charge on the antenna.  A DC path between the coax center conductor
and shield will do wonders to minimize that charge.  A high value
resistor (5 k to 10k) or an RF Choke of 100 uHy value will provide an
adequate DC path.  That resistor can be placed inside an antenna switch
or can be installed directly at the KPA100 SO-239 jack with a TEE
adapter.  Mount the choke or resistor into a PL-259 body and connect it
to one side of the TEE adapter, the other side connects to the antenna.  
That will provide protection from normal antenna static buildup, but if
there is evidence of nearby lightning, disconnecting the antennas is the
only solution that will prevent damage.

73,
Don W3FPR

On 2/22/2011 8:51 PM, Curt Milton wrote:

> My K2 seems to be working fine -- the KAT100 is working, and it is transmitting
> full power.  But there is no power indication on the LED meter, and instead I
> get a high current warning even though all is well.  This just turned up today
> on 'an old K2.'  It is misbehaving at all power levels - woops I just figured
> out the power control does not seem to be working when I am above 'QRP'
> settings.  The rig was only moved a few inches since it was last used.  Has
> anyone else experienced this ?
>
> 73 Curt
>
>
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
>

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