As promised, here's my "no match" update report.
I checked all coax connections and, even though it's not conclusive,
could see no corrosion, so I started replacing the various lengths of
coax between one piece of equipment and another.
To make it short and sweet, if I remove my station monitor (SM-220)
from the antenna circuit my 940 has no problem finding a "match."
Apparently there is some condition within the station monitor that is
causing the problem. It doesn't matter if I have the monitor on or off.
it won't match above 28.4.I have no idea what this condition could be at
this time, but as long as it's not my rig it's no biggy. I can check out
the SM-220 when time permits. I don't use it too often anyway.
Once again I find myself relearning the lesson of "always check the
simple things first."
Of course, this raises the question to me of why does it match with
the 20 meter dipole and not the 10 meter dipole, but there's probably a
simple solution there, too.
I extend my thanks to all of my brother hams who made the effort and
took the time to offer their input and help me find the solution to my
"match" problem.

73
Charlie Shaw
KB3BTO

Dee D. Flint wrote:

"Charles J. Shaw" wrote in message
...

I understand what you're saying, but everything was working fine,
for several years, and now it's not. The rig, the feed line, and the
antenna - a 10 meter dipole - have not changed in obvious physical
condition.
The last time that this happened, I took the rig into a repair shop.
I was told that it, "was just some carbon build-up on the relay." I
don't know if this was the cause, but the bill didn't add up to much, so
I assumed that this was the case. I felt a little stupid for not
considering something this obvious (always check the simple things
first, right?), but I just packed it away as one of life's little lessons.
I checked the relay on the tuner and sprayed it with some contact
cleaner, but the problem still exists. I "should" be able to fix this. I
think that I'm just overlooking something...but what?
I thank you for your response.

Gary, I did a little copy and paste move to post this to your
message as well as the message from G4FGQ. I think that it sums up the
situation. Do you see any that I might be overlooking? It comes up as
something relatively simple, but I'm missing it and it's making me nuts!

Charlie Shaw
KB3BTO

Gary McAdams wrote:


"Charles J. Shaw" wrote in message:


My Kenwood 940 is failing to find a "match" when I engage the auto
tuner.


Charlie,

The first thing to remember is that the 940's tuner, like most built-in
tuners has a fairly limited range. I have been able to tune a tri-bander
on 160, but that does not mean that the tuner was designed to do it.

What I did, whenever the built in tuner would not match, was this:

1. Meter switch to SWR.

2. AUTO/THRU to AUTO position.

3. Press AT.T.

4. Observe SWR readings on meter. You will note that the meter
readings go up and down as the tuner attempts a match.
when SWR hits an acceptable level, i.e., between 2:1 and
1.5:1, disengage tuner by pressing AUTO/THRU button.

5. After tuner stops, re-engage tuner using the AUTO/THRU button,
go to rtty/am/fm. Set power to lowest level. Transmit and check SWR.

6. If the SWR is still OK, then operate. If not try the cycle again.

The software in the 940 is trying to get to the 1:1 SWR level. This
is simply not always possible given the limited matching
capability ofthis tuner and the unlimited types of loads that
could be presented at the antenna. 1.5:1 or even 2:1 is acceptable
to the finals, but not to the AT software routine.

Then there is the real possibility that you might have a problem
in the tuner/radio combination. If you observe the meter while
the tuner is in operation and see no variance in readings, or
hear no activity of the tuner, then there might be a problem.

73, Gary WG7X




Even though nothing obvious may have changed with the antenna, get hold of
an antenna analyzer and check it. The connection of the feedline to the
antenna may have deteriorated. If you are using coax, water may have gotten
in the line. The joints of the connectors to the line may have
deteriorated. The MFJ antenna analyzer lets you check the impedance and
loss of the line itself. You have to disconnect the line from the antenna
when you are checking the line only.

Note if you had a carbon buildup before, that indicated something else was
wrong with your system. Carbon occurs when something burns. Quite possibly
your tuner has been arcing because something is off with the antenna and has
always been off. Then when the carbon builds up, it won't work.

If you are using a properly cut 10m dipole on 10meters, you really shouldn't
need the tuner at all unless you are at the extremes of the band. What is
your SWR reading when you don't use the tuner?

Dee D. Flint, N8UZE