My Kenwood 940 is failing to find a "match" when I engage the auto
tuner. Has anyone else run into this problem and come up with a solution
beside sending it out for repair?

73
KB3BTO
Charlie Shaw

"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

"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

Try giving the auto-tuner a little external assistance.

Connect a few micro-henrys or a capacitor in series or in parallel with the
transmission line at the antenna end of the tuner. This will often shift
the line input impedance into a range which the auto-tuner can accommodate.

Or try changing the length of the line by a few feet.


If the line input impedance is measured it can be deduced what sort of
additional component is needed for one awkward band. It may not adversely
affect other bands.


In the worst case situation you can always prune the antenna. Never give
up.
----
Reg, G4FGQ

Try giving the auto-tuner a little external assistance.

Connect a few micro-henrys or a capacitor in series or in parallel with the
transmission line at the antenna end of the tuner. This will often shift
the line input impedance into a range which the auto-tuner can accommodate.

Or try changing the length of the line by a few feet.


If the line input impedance is measured it can be deduced what sort of
additional component is needed for one awkward band. It may not adversely
affect other bands.


In the worst case situation you can always prune the antenna. Never give
up.
----
Reg, G4FGQ

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.

Charlie Shaw
KB3BTO

Reg Edwards wrote:
Try giving the auto-tuner a little external assistance.

Connect a few micro-henrys or a capacitor in series or in parallel with the
transmission line at the antenna end of the tuner. This will often shift
the line input impedance into a range which the auto-tuner can accommodate.

Or try changing the length of the line by a few feet.


If the line input impedance is measured it can be deduced what sort of
additional component is needed for one awkward band. It may not adversely
affect other bands.


In the worst case situation you can always prune the antenna. Never give
up.
----
Reg, G4FGQ

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.

Charlie Shaw
KB3BTO

Reg Edwards wrote:
Try giving the auto-tuner a little external assistance.

Connect a few micro-henrys or a capacitor in series or in parallel with the
transmission line at the antenna end of the tuner. This will often shift
the line input impedance into a range which the auto-tuner can accommodate.

Or try changing the length of the line by a few feet.


If the line input impedance is measured it can be deduced what sort of
additional component is needed for one awkward band. It may not adversely
affect other bands.


In the worst case situation you can always prune the antenna. Never give
up.
----
Reg, G4FGQ

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

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

On Wed, 31 Dec 2003 01:56:39 GMT, "Charles J. Shaw"
wrote:

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.

What band(s) are you trying to match to your 10 meter dipole?

Bob
k5qwg