[Elecraft] KPA1500 RFI on 12m

[Martin Sole]

I use a C3 up at 80 feet it works quite well. I have not really spent a 
lot of time on 12m, really no activity here to make it worthwhile but on 
17m it works rather well despite not being a particularly good match. I 
fixed that by measuring the actual impedance at the end of my feeder 
then adding a foot or so of feeder and cutting a shorted stub to create 
a good match. In my case it's very close to perfect but anything less 
than 1.5:1 I would consider excellent.

An antenna analyser and 5 minutes with the excellent SimSmith program 
can do wonders for your matching worries. Properly sorted at just the 
right point on the feeder with an antenna switch a tee piece and a few 
stubs you could probably get a good match on a bunch of bands though I 
suspect the losses might be a bit high if you try 40m, eek!

The C3 on 17m certainly has directivity albeit 180 degree from the 
regular 20-15-10 antenna.

Martin, HS0ZED






On 25/10/2019 03:08, 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?  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
>
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