[Elecraft] UPDATE KPA1500 on 160M

[James Bennett]

Ronnie,

I’m kinda late to this dance, but did want to toss in my thoughts. I assume you are running a length of beefy coax from the back of the KPA1500 to the balun. I do the same with my KPA500/KAT500. About 10 feet of 9913 coax to the Balun Designs box, then 110 feet of 600 ohm line to the antenna feed point. I initially had a very ugly SWR on 20 meters that the KAT500 balked at; the other bands were fine. Changing the length of the coax between the tuner and the balun cured the problem - I went from 20 feet (a convenient piece of coax I had lying around) to 10 feet. If you’ve got some other lengths of coax available, you might want to try switching them in / out - might be easier than chopping the ladder line.

73, Jim / W6JHB



> On Sep 2, 2020, at 6:06 PM, Jim Miller <jtmiller47 at gmail.com> wrote:
> 
> Have you measured the impedance presented to the amplifier with an antenna analyzer?
> 
> Jim ab3cv 
> 
> On Sep 2, 2020, at 9:03 PM, Adrian <vk4tux at gmail.com <mailto:vk4tux at gmail.com>> wrote:
> 
> Ronnie, well done. Moving to a different ratio balun is a smart obvious move towards obtaining a better match,
> 
> especially at higher power maintaining insulation specs required.
> 
> From curiosity what was the model number of the BD 4:1 balun you had initially please ?
> 
> 
>> On 3/9/20 10:03 am, Ronnie Hull wrote:
>> The original thread has gone off on some tangents. I truly appreciate all the suggestions.
>> 
>> I seem to have cured the problem!
>> 
>> ORIGINAL ISSUE was using a new W7FG 160m doublet with 600 ohm true ladder line. The ladder line was hooked to a Balun Design 4:1 ( as recommended by the seller of the antenna). The antenna would be matched great in 160M by the internal ATU in the K3 but with the KPA1500 inline it all went north really fast, resulting in the 1500 faulting out
>> 
>> Earlier today I swapped in a DX Engineering maxi core 4:1 and it worked a hell of a lot better but the KPA1500 still could not match it better than 9:1
>> 
>> Mind you this antenna matches superb on other bands with the KPA1500
>> 
>> Also the KPA1500 works great into a dummy load so I knew the issue was the antenna or part of it
>> 
>> Last I put in line a DX Engineering maxi core 6:1 and BAM... it worked!
>> The KPA1500 matches to 2.5:1 which is good enough for now.
>> 
>> Next I will experiment with the 600 ohm ladder line length. Right now I’m using 57’.  I will add 10’ tomorrow and see what shakes out and will let you fellas know
>> 
>> Thanks for all the help and suggestions!
>> 
>> Ronnie W5SUM
>> 
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