I was looking at a MFJ remote antenna tuner, and it is specified as being
able to match 12 to 1600 ohms.

What does that mean? At 12 ohms the SWR would be about 4.2:1 and at 1600
ohms a SWR of about 32:1.

If one started from 1600 ohms around a Smith chart, the circle would
intersect at the other side at about 0.64 ohms.

Likewise starting at 12 ohms and going halfway around the chart would end up
at 210 ohms, not 1600.

How does one use the specs if the antenna to be matched has a complex
impedance? Look at the internal tuner component ranges?

Wayne wrote:
I was looking at a MFJ remote antenna tuner, and it is specified as being
able to match 12 to 1600 ohms.

What does that mean? At 12 ohms the SWR would be about 4.2:1 and at 1600
ohms a SWR of about 32:1.

If one started from 1600 ohms around a Smith chart, the circle would
intersect at the other side at about 0.64 ohms.

Likewise starting at 12 ohms and going halfway around the chart would end up
at 210 ohms, not 1600.

How does one use the specs if the antenna to be matched has a complex
impedance? Look at the internal tuner component ranges?

Those ranges of impedances are basically worthless.

Looking at the component ranges is probably the best, but most complex
way.

Some makers give half way usefull info with things like will tune
a minumum of X feet long at 160 M.

I have both a SGC and a LDG; the SGC is much better range wise.


--
Jim Pennino

On 8/9/2015 12:23 PM, Wayne wrote:
I was looking at a MFJ remote antenna tuner, and it is specified as
being able to match 12 to 1600 ohms.

What does that mean? At 12 ohms the SWR would be about 4.2:1 and at
1600 ohms a SWR of about 32:1.

The 12 to 1600 ohms is the RANGE that the tuner is capable of matching.
Forget SWR because it has no meaning at this point.

If one started from 1600 ohms around a Smith chart, the circle would
intersect at the other side at about 0.64 ohms.

You are not analyzing this correctly. If you are really comfortable with
a Smith chart, put a capacitor across the 1600 ohms and then put an
inductor in series with the results. By adjusting the values, you can
achieve a 50 ohm output.

Likewise starting at 12 ohms and going halfway around the chart would
end up at 210 ohms, not 1600.

This is similar to the above, but now you want a series impedance and a
shunt impedance following it.

How does one use the specs if the antenna to be matched has a complex
impedance? Look at the internal tuner component ranges?

That is a good question. Do you want to buy the tuner and tear it down
to explore the component ranges, or would it be better to ask the
designers? You should ask them to define the type (complex impedance) of
the load to which their specs apply.

"John S" wrote in message ...

On 8/9/2015 12:23 PM, Wayne wrote:
I was looking at a MFJ remote antenna tuner, and it is specified as
being able to match 12 to 1600 ohms.

What does that mean? At 12 ohms the SWR would be about 4.2:1 and at
1600 ohms a SWR of about 32:1.

The 12 to 1600 ohms is the RANGE that the tuner is capable of matching.
Forget SWR because it has no meaning at this point.

That's a bit of what I was getting at. I have another tuner rated for 4:1
SWR, and I assume that means it will match all the way around the 4 circle.

I don't know what to do with a 12 to 1600 ohm spec.



If one started from 1600 ohms around a Smith chart, the circle would
intersect at the other side at about 0.64 ohms.

You are not analyzing this correctly. If you are really comfortable with a
Smith chart, put a capacitor across the 1600 ohms and then put an inductor
in series with the results. By adjusting the values, you can achieve a 50
ohm output.

Likewise starting at 12 ohms and going halfway around the chart would
end up at 210 ohms, not 1600.

This is similar to the above, but now you want a series impedance and a
shunt impedance following it.

I was just showing that the 12 and 1600 are not on the same circle.



How does one use the specs if the antenna to be matched has a complex
impedance? Look at the internal tuner component ranges?

That is a good question. Do you want to buy the tuner and tear it down to
explore the component ranges, or would it be better to ask the designers?
You should ask them to define the type (complex impedance) of the load to
which their specs apply.

I suspect the designers have a gag order from the marketing guys.

wrote in message
...
Wayne wrote:
Those ranges of impedances are basically worthless.
I don't agree :-)
If I had to test such a tuner the first thing I would do
is put a pure resistor of those values and try to
match them accross the frequency and power range announced.
Measuring the insertion loss would be nice too.
Of course it is not the complete story but a good start.

"bilou" wrote in message ...


wrote in message
...
Wayne wrote:
Those ranges of impedances are basically worthless.
I don't agree :-)
If I had to test such a tuner the first thing I would do
is put a pure resistor of those values and try to
match them accross the frequency and power range announced.
Measuring the insertion loss would be nice too.
Of course it is not the complete story but a good start.

That's true, but I would like for the specs to give me an idea if I want to
buy it.

bilou wrote:

wrote in message
...
Wayne wrote:
Those ranges of impedances are basically worthless.
I don't agree :-)
If I had to test such a tuner the first thing I would do
is put a pure resistor of those values and try to
match them accross the frequency and power range announced.
Measuring the insertion loss would be nice too.
Of course it is not the complete story but a good start.

Which basically tells you nothing about the ability to match a complex
load.

I measured the impdance of a vertical to be well under the specified
limits of the LDG tuner I own. However, it fails to get a match on
160 M and 17 M.

The SGC tuner has no problems getting a match.



--
Jim Pennino

On 8/9/2015 4:24 PM, Wayne wrote:


"John S" wrote in message ...

On 8/9/2015 12:23 PM, Wayne wrote:
I was looking at a MFJ remote antenna tuner, and it is specified as
being able to match 12 to 1600 ohms.

What does that mean? At 12 ohms the SWR would be about 4.2:1 and at
1600 ohms a SWR of about 32:1.

I don't know what to do with a 12 to 1600 ohm spec.



If one started from 1600 ohms around a Smith chart, the circle would
intersect at the other side at about 0.64 ohms.

Likewise starting at 12 ohms and going halfway around the chart would
end up at 210 ohms, not 1600.

I was just showing that the 12 and 1600 are not on the same circle.

Now I think I understand your point. I had not considered that you are
thinking in terms of the matching capability using SWR circles on the
chart. Very interesting and quite useful if the specs can be assumed to
mean that.

I have a gut feeling that the 1600 is a bit far out and that the 12 is
more realistic, but I have never used a tuner. My stuff was always
one-band designed so just fixed matching values suited.

If I learn anything I get back to you. Sorry I couldn't help.

On 8/9/2015 12:23 PM, Wayne wrote:
I was looking at a MFJ remote antenna tuner, and it is specified as
being able to match 12 to 1600 ohms.

What does that mean? At 12 ohms the SWR would be about 4.2:1 and at
1600 ohms a SWR of about 32:1.

If one started from 1600 ohms around a Smith chart, the circle would
intersect at the other side at about 0.64 ohms.

Likewise starting at 12 ohms and going halfway around the chart would
end up at 210 ohms, not 1600.

How does one use the specs if the antenna to be matched has a complex
impedance? Look at the internal tuner component ranges?

What antenna are you thinking to match?

In article ,
"Wayne" wrote:

I was looking at a MFJ remote antenna tuner, and it is specified as being
able to match 12 to 1600 ohms.

What does that mean? At 12 ohms the SWR would be about 4.2:1 and at 1600
ohms a SWR of about 32:1.

If one started from 1600 ohms around a Smith chart, the circle would
intersect at the other side at about 0.64 ohms.

Likewise starting at 12 ohms and going halfway around the chart would end up
at 210 ohms, not 1600.

How does one use the specs if the antenna to be matched has a complex
impedance? Look at the internal tuner component ranges?

Wayne-

Your Smith Chart is normalized to 50 Ohms, but the tuner may not have a
"characteristic impedance". So to use the Smith Chart approach, assume
that it does. In that case, Z divided by 12 is equal to 1600 divided by
Z. Therefore Z squared is equal to the product of 12 and 1600, or Z =
138.6 Ohms.

You can normalize a Smith Chart to that value. Now see if the tuner
will work with all values within the circle!

Fred
K4DII