Re: NOT the feedline

Posted by Peter W2IRT on Jun 02, 2020; 3:49pm
URL: http://elecraft.85.s1.nabble.com/Re-NOT-the-feedline-was-KPA-1500-faulting-on-6m-SWR-issues-tp7661502p7661579.html

Just to clarify, I was **NOT** using the tuner to tune the 6m antenna
system. I was using it as a coax switch, so I could keep the KPA-1500
powered down (silencing the very noisy PSU fan) and still be able to receive
6m as well as other bands.

I need the room to be quiet since my XYL is working-from-home a few feet
away from me in the same room, and the KPA's power supply fan is bothersome
to both her and me.

Ideally, the KPA-1500 should be able to default to either ANT-1 or ANT-2 in
power-down mode but that is not the case. So I need a quiet alternative. I'm
not a fan of tuners of any kind.

In any event, the TT-238 is out of line now and the SWR problem is
MARGINALLY better on the KPA-1500. It's still showing a higher SWR than the
antenna analyzer measured but it hasn't folded back yet.


 - pjd

-----Original Message-----
From: [hidden email] <[hidden email]> On
Behalf Of Mark Goldberg
Sent: Tuesday, June 2, 2020 2:10 AM
To: Bob McGraw K4TAX <[hidden email]>
Cc: Elecraft Mailing List <[hidden email]>
Subject: Re: [Elecraft] NOT the feedline

I want to mention that my LDG AT-600Pro has a minimum capacitance that is
too high for a good match to my antenna on 6 meters. Certainly seems like
removing the Ten Tec tuner would be a good thing to try. Can you open the
Ten Tec tuner and use an IR thermometer to monitor the components? I don't
know anything about it's construction. You could see them heating up.

Just running medium power of maybe 500W would slow things down and let you
see the SWR increasing before the amp trips. That would confirm that
something is heating up vs arcing.

73,

Mark
W7MLG

On Mon, Jun 1, 2020 at 9:01 PM Bob McGraw K4TAX <[hidden email]> wrote:

> Plus there is L1 which is 0.3uH in the circuit and C7 and C8 in the
> circuit when in the bypass position.  This does not allow the tuner,
> even in bypass mode, to work well as an antenna switch on 6M.
>
>   The capacitors in question are not rated for the RF current
> experienced under certain load Z conditions.  They heat, change value,
> and the SWR creeps up.  Allow them to cool and the SWR is back to the
> starting point.    I usually tweaked mine such that the SWR started off
> a bit high, came down as I transmitted and if transmitting a bit longer
> the SWR increased.   Later I got tired of this and changed the group of
> disk ceramic caps to 470 pf Russian doorknob caps.  Problem solved.
>
> 73
>
> Bob, K4TAX
>
>
> On 6/1/2020 10:08 PM, Jim Brown wrote:
> > his might be it, Peter. ! I've used (and loved) the Ten Tec 229 and
> > 238 tuners, but some of their fixed capacitors are under-rated for
> > power. This is fairly well known among Ten Tec users, so I read
> > about it somewhere and replaced those in my tuners with caps having
> > higher power ratings.
>
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