I would first check the parameters of the tuners using the KAT500
utility. If the tune routine is done with 100 watts or more (per the
manual) will cause a fault condition. The tune power should be
between 7 and 30 watts. At 30 watts and above the ATU will not open the
amp key line and may be the cause of relay damage.
In the KAT500 Utility program one can select the SWR threshold value.
Typical values are 2.5:1 or 3.0:1. I suggest one review their
configuration, amp key control method if used, and power used for
tuning. I don't recall the relays being reed type relays but ones which
are much more robust.
I find that optimum TUNE power should be about 20 to 25 watts and no
more. By all means, any amp should be in the bypass mode when the TUNE
routine is initiated.
What transceiver and what amp are being used with the KAT500?
73
Bob, K4TAX
On 7/19/2025 11:00 AM, [email protected] wrote:
Message: 7
Date: Fri, 18 Jul 2025 20:28:48 -0800 (PST)
From: dave ingebright<[email protected]>
To:"[email protected]" <[email protected]>
Subject: [Elecraft] Two KAT 500s Intermittent High SWR
Message-ID:<[email protected]>
Content-Type: text/plain; charset=UTF-8
I own two Elecraft KAT500 autotuners (main and spare) They are finding erratic
solutions on all three antenna outputs and then fault due to high SWR. It's
driving me crazy due to both exhibit the same problem. One will find a solution
one day, but not the next, or an hour later on the same or a different band.
New coax runs. If I connect the cantenna to the end of the coax next to the
antenna, same condx. Then I go back to it and it's OK.
So today I caught it. Started transmitting, and ATU went to full HIGH SWR and
then into fault mode. Checked the antenna and nothing amiss. I think the small
reed relays that tune the match are arcing or opening up. You guys know there
are some high voltages in these tuners as they tune and operate. How does
Elecraft handle this in their design?
I still think these are the best autotuners on the market, but what the heck. I
have two of these exhibiting the same symptoms. Checked the catalog, $1024 on
sale $25 off. Sheesh
Guess I will call the tech line and see what they say...
//dave
WB7ELY
--
Retirement: It's nice to get out of the rat race, but you have to learn
to get along with less cheese.
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