Help with troubleshooting KAT1

[Jason Artz]

Hello,

I have a new K1-4 that I built over the last couple
weeks and it seems to work fine.  It passed all its
tests.  Since I don't have an antenna, I went ahead
and built the KAT1 so that I could get on the air.  I
think I'm having a problem with it, but I am not sure
since I don't yet have an RF probe and can't do all of
the tests/calibrations.

The initial test worked - the KAT1 is communicating
with the K1 properly.

The SWR bridge adjustment, I believe, is where I'm
having a problem.  With the dummy load, my SWR in CLS
mode reads about r4.5 or so.  Adjusting C9 changes
voltage in a very narrow range (about 1.3-1.5v).  I
set it for the lowest voltage reading.  

I haven't done the power calibration yet, but if I try
tuning a wire antenna (in "tun" mode), I get a lot of
relay chattering, displayed power level fluctuation,
and eventual r9.9.   Same with the dummy load on all
bands.  All relays work - when I step through the
various L0, L1, etc., they click and I can hear a
difference in received noise level.

Will my problems be taken care of in the power
calibration step, or might I have something else going
on?

Thanks for your help,
Jason
AC6XA


               
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[Tom Hammond-3]

Hi Jason:

You should definitely get less than a 4:1 SWR when using a decent
dummyload. Something closer to 1:1 or 1.1:1 would be expected.

Here are a couple suggestions IF you can implement them:

1) Check the real resistance of your dummyload!!! It should be between 45
and 55 Ohms. If not, MAKE a new one from a couple 100 Ohm 2W (or 3W) metal
oxide resistors. If you can't find metal oxides locally, use a couple 100
Ohm 2W carbon comp or metal films.

2) Do away with ANY coax between the rig and the dummyload...! Several
times I've seen even moderate coax length 'get in the way' of even
semi-accurate SWR null adjustments. If your dummyload will allow it,
directly connect it to the back of the ATU via a BNC to (whatever) adapter.
If not, use the very shortest length of coax you can achieve.

3) Use an analog meter when setting the null... of course it will have to
be pretty sensitive... if you don't have one, use whatever you have.

4) Ensure that the null you're seeing occurs at a point which is NOT at one
of the two tuning extremes of the cap (not at fully open or fully closed).
If it is, then you have a problem elsewhere... often in the transformer of
the directional coupler.

Good luck,

Tom Hammond   N0SS




At 09:18 AM 5/6/05, Jason Artz wrote:

>Hello,
>
>I have a new K1-4 that I built over the last couple
>weeks and it seems to work fine.  It passed all its
>tests.  Since I don't have an antenna, I went ahead
>and built the KAT1 so that I could get on the air.  I
>think I'm having a problem with it, but I am not sure
>since I don't yet have an RF probe and can't do all of
>the tests/calibrations.
>
>The initial test worked - the KAT1 is communicating
>with the K1 properly.
>
>The SWR bridge adjustment, I believe, is where I'm
>having a problem.  With the dummy load, my SWR in CLS
>mode reads about r4.5 or so.  Adjusting C9 changes
>voltage in a very narrow range (about 1.3-1.5v).  I
>set it for the lowest voltage reading.
>
>I haven't done the power calibration yet, but if I try
>tuning a wire antenna (in "tun" mode), I get a lot of
>relay chattering, displayed power level fluctuation,
>and eventual r9.9.   Same with the dummy load on all
>bands.  All relays work - when I step through the
>various L0, L1, etc., they click and I can hear a
>difference in received noise level.
>
>Will my problems be taken care of in the power
>calibration step, or might I have something else going
>on?
>
>Thanks for your help,
>Jason
>AC6XA
>
>
>
>__________________________________
>Do you Yahoo!?
>Yahoo! Mail - Helps protect you from nasty viruses.
>http://promotions.yahoo.com/new_mail
>_______________________________________________
>Elecraft mailing list
>Post to: [hidden email]
>You must be a subscriber to post to the list.
>Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft
>
>Help: http://mailman.qth.net/subscribers.htm
>Elecraft web page: http://www.elecraft.com

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