[Elecraft] KX1 ATU Problem Revisited

Sun Dec 7 14:33:00 2003

I sent this to Wayne this AM.  On the off chance he is off somewhere, I 
am posting it here, too.

The problems noted in my original message appeared to have been resolved 
by simpling removing and replacing the ATU PCB.  I'm thinking that 
perhaps the process of soldering the PCB to the installed (in the main 
PCB) plugs may have cause oxidation or some other reason for marginal 
connection at one of the pins.

But, even though it is working differently now (L and C not always zero 
after a tune), one thing troubles me.

I connect antenna A and the tuner does a reasonable job of matching it 
(say swr of 1.5:1 or r1.5).  Now I again tune without doing anything 
else, and the relays operate and come up with the same result.  It seems 
like the relays should not operate if they are already at the correct 
setting when I initiate Tune.  At least that is how the other ATUs seem 
to work.

Plus if I replace antenna A by a dummy load,  the relays do NOT operate 
and r is 1.0

Am I correct in concluding that my KXAT1 is not operating properly?  If 
so, what should I be looking for?  I've done all the troubleshooting 
steps and all seems normal there.  And I am getting a null of 10 mV or 
so with the trimmer.

I hesitate to tear into it without your confirmation that it is no 
working correctly (maybe this is how you designed the firmware) and 
advice as to how to proceed?

73, Phil

-------- Original Message --------
Subject: 	Re: [Elecraft] Probable KXAT1 Problem
Date: 	Sat, 06 Dec 2003 16:59:01 -0800
From: 	Phil Wheeler <[email protected]>
Reply-To: 	[email protected]
To: 	Elecraft <[email protected]>
References: 	<[email protected]>

Regarding the following, it appears I fixed it.  My first thought was to 
remove the atu pcb and look it over for unsoldered joints, etc.  All 
looked good.

Then it occured to me that I had had a similar problem with a pcb in the 
K2 which was cured by an R&R of the board.

Apparently that worked here, too.

The assembly process -- inserting the plugs in the main board and 
installing the atu pcb on the plugs may have had something to do with 
it.  Likely if I had done an R&R as part of the assy process, I would 
not have had this problem.  Who knows?

In any case, I now get non zero values of C and L after a tuneup and r 
is indicating the result of tuning, not the swr of the untuned antenna.

If only all my troubles and errors were so easy to fix :-)

73, Phil

Phil Wheeler wrote:

> When building the atu, it passed all checks.  I even went through all 
> the Troubleshooting steps on page 11 of the manual.  So all seemed 
> OK.  And I thought all was good, since it loaded the antenna I was 
> using well. BUT -- that antenna is pretty much 1.0:1 where I operate, 
> so I suspect that led to a false sense of success.
>
> Now I am trying the rig with a variety of wires and balanced antennas 
> and I am coming to suspect that the atu is not working correctly.
>
> Consider three cases (from among many):
>
> Antenna A (beam): MFJ analyzer says it is 2.0:1 on 14050
>
> Antenna B (D4 multiband dipole): MFJ says 1.2:1
>
> Dummy load:  1.0:1
>
> Scenario is as follows:
>
> 1.  I connect Antenna A and push Tune.  Relays clatter away and 
> eventually stop.  Indication is r2.2
>
> 2.  I connect either Antenna B or the dummy load: Relays do nothing. 
> Indication is r1.0
>
> 3.  I reconnect Anenna A.  More clattering and r2.2 results.
>
> Then I read the L and C using the ATU menu.  I get L.00 and C.00
>
> I would expect very different behavior and result.  r should indicate 
> the swr after tuning, not that of the untuned antenna.  And L, C of 00 
> does not look right when loading an antenna with an inherent swr of 
> 2:1 or so.
>
> It is basically as though the atu, while making the dutiful noises, is 
> not matching the antenna.  BTW -- band does not matter; I just chose 
> 20 m for this data set.
>
> Now I know why my initial attempts to load a 24 ft wire a few days ago 
> were so odd.  I think the atu is not doing what it is supposed to.
>
> Since I have done all the troubleshooting steps with the expected 
> results re C and L readings, relay switching and so on, adjusted R1 
> and R2 according to the manual, etc. -- where should I look for this 
> problem?
>

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