Re: NOT the feedline

Posted by Ted Edwards W3TB on Jun 02, 2020; 12:08am
URL: http://elecraft.85.s1.nabble.com/Re-NOT-the-feedline-was-KPA-1500-faulting-on-6m-SWR-issues-tp7661502p7661547.html

Back to Bob K4TAX
I had a common mode current problem when I lived in Virginia and ran 100
watts barefoot, and it came as I could not do a significant angle away from
the antenna --- which I eventually solved.

I really do love the OCF idea.  Through modeling it and patterns and then
careful selection of trees for directionality, I have been able to land the
lobes on Europe, South America, and East Asia for 40m, 20m, and 15m with
upwards of 8 dBi --- not too shabby for a wire antenna.

I have some LMR-400 and RG-9 B/U here and plan to change out the coax.  I
no longer expect that work to solve the issue, so I am looking at baluns.
While it is a change back from a current balun to voltage balun, I must may
do it.

Thanks for all the good wisdom, guys!

On Mon, Jun 1, 2020 at 6:33 PM David Gilbert <[hidden email]> wrote:

> I had an antenna for 160m that had a fairly high SWR at the feedpoint, but
> was easy to match to 50 ohms with a series inductor less than 30 feet
> further down the line toward the shack.  I put a common mode choke per
> K9YC's designs at the antenna feedpoint, though, and even though it was
> actually two chokes in series (two large cores with separate windings) that
> should easily handle 5 KW under matched conditions, at 1.5 KW it heated up
> in less than two seconds to put the QRO Tech HF-2500DX amp into a fault.  I
> could have moved the choke to the shack side of the matching inductor, but
> I decided it was best to just fix the antenna.  No problems after I did.
>
> Common mode chokes don't need high saturation current to get hot (and
> that's rarely the problem anyway) ... high SWR voltages work just fine for
> that.  And at high power it can happen in a very brief period of time.
>
> Everyone stay safe,
> Dave   AB7E
>
>
> >
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--
73 de Ted Edwards, W3TB and GØPWW

and thinking about operating CW:
"Do today what others won't,
so you can do tomorrow what others can't."
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