[Elecraft] KPA1500 RFI on 12m

[Jim Brown]

On 10/24/2019 1:08 PM, eric norris via Elecraft wrote:
> My Force 12 C3 antenna is not resonant on 12m.  Using the K3 barefoot, the internal atu tunes the antenna fine.  Bypassing the K3 atu, but still running barefoot into the KPA1500 atu, the KPA atu loses it's mind and goes in and out of TUNE mode uncommanded.  Even though the KPA has found a match, trying to transmit through it at the 100w level is impossible because of the constant retuning.
> I have put my small collection of mix-31 ferrites on the antenna output, input, and KPA control line at the KPA, each at a time, with no success.  Any ideas?

Yes. First, and most important, the place for the common mode choke is 
at the antenna feedpoint, NOT in the shack, and it must be a 
well-designed multi-turn choke. http://k9yc.com/2018Cookbook.pdf

Second, make sure that you entire station is properly bonded, 
chassis-to-chassis of all interconnected equipment, and that operating 
desk bonded to every ground in your home.
http://k9yc.com/GroundingAndAudio.pdf

Also, this is a good time to verify that EVERY  coax connector and 
adapter has its shield well terminated (well soldered or properly 
crimped) and that all solder-type connectors are an Amphenol 83-1SP. 
Make sure that all adapters are Amphenol or have a MIL-spec part number 
stamped on them. Off-brand connectors are often junk, and often cause 
problems like what you're seeing. Also make sure that every connector is 
wrench-tight.

Station design issues like these may not show up at low power but cause 
problems with high power.

73, Jim K9YC

   I would like to be able to run the KPA at least a few hundred watts 
to have the proverbial snowball's chance to break the VP6R pileup on 12m CW.
> Any useful comments appreciated.
> 73 Eric WD6DBM
> 
> Sent from Yahoo Mail on Android
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:Elecraft at mailman.qth.net
> 
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to jim at audiosystemsgroup.com
>