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?

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.

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 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.

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.

I found the following on the MFJ site for the MFJ-998RT. See page 2 at
this link:

http://www.mfjenterprises.com/Downlo...df&company=mfj

•Impedance matching range: 12 to 1600 ohms
•SWR matching range: up to 4:1 for 50 ohms and upto 32:1 for 50 ohms
•Minimum power for tuning: 5 watts
•Maximum power while tuning: 100 watts with foldback, 20 watts without
foldback
•RF power limit: 1500 watts SSB/CW
•Frequency range: 1.8 to 30 MHz continuous coverage
•Frequency counter accuracy: ±1 kHz across HF bands

•Capacitance range: 0 to 3926 pF nominal (256 values) on input side 0 to
976 pF nominal (64 values) on output side

•Inductance range: 0 to 24.28 µH nominal (256 values)

On 8/11/2015 6:18 PM, John S wrote:
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.

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.

I found the following on the MFJ site for the MFJ-998RT. See page 2 at
this link:

http://www.mfjenterprises.com/Downlo...df&company=mfj


•Impedance matching range: 12 to 1600 ohms
•SWR matching range: up to 4:1 for 50 ohms and upto 32:1 for 50 ohms
•Minimum power for tuning: 5 watts
•Maximum power while tuning: 100 watts with foldback, 20 watts without
foldback
•RF power limit: 1500 watts SSB/CW
•Frequency range: 1.8 to 30 MHz continuous coverage
•Frequency counter accuracy: ±1 kHz across HF bands

•Capacitance range: 0 to 3926 pF nominal (256 values) on input side 0 to
976 pF nominal (64 values) on output side

•Inductance range: 0 to 24.28 µH nominal (256 values)

I think their minimums are not realistic. I would not know how to
achieve 0pF with a 3926pF variable cap, for example. Also, why 3926
rather than 3900 or even 3920? It isn't all that easy to measure 6pF out
of 3920pF. I'm thinking that somebody just threw some numbers at the
spec sheet.

BUT! It is better than nothing and may help to make some reasonable
judgements.

In article , John S wrote:

I think their minimums are not realistic. I would not know how to
achieve 0pF with a 3926pF variable cap, for example. Also, why 3926
rather than 3900 or even 3920? It isn't all that easy to measure 6pF out
of 3920pF. I'm thinking that somebody just threw some numbers at the
spec sheet.

BUT! It is better than nothing and may help to make some reasonable
judgements.

Typically, these tuners use banks of capacitors, switched in and out
(parallel for caps, series for inductors) using relays. The
components are often in a 1:2:4:8:... power series. "256 values"
implies 8 components, and 8 relays, giving you anywhere from 0 to 255
times the "fundamental" value.

I expect that "0" means "all caps open, or all inductors shorted",
and "3926" is the sum of the nominal values of the caps in the bank.
If their starting value is around 15 pF, 255 times that would be
3825; add in a few pF of stray capacitance per relay and you'd be
in the neighborhood of 3926.

(Having figures like that, in the face of component variations and
strays and measurement errors, reminds me a bit of some dialog from
Harry Harrison's "Star Smashers of the Galaxy Rangers."

"[certain ancient events] took place approximately 14 billion years
ago."

"That figure is exact?"

"Of course."
)

John S wrote:
On 8/11/2015 6:18 PM, John S wrote:
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.

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.

I found the following on the MFJ site for the MFJ-998RT. See page 2 at
this link:

http://www.mfjenterprises.com/Downlo...df&company=mfj


?Impedance matching range: 12 to 1600 ohms
?SWR matching range: up to 4:1 for 50 ohms and upto 32:1 for 50 ohms
?Minimum power for tuning: 5 watts
?Maximum power while tuning: 100 watts with foldback, 20 watts without
foldback
?RF power limit: 1500 watts SSB/CW
?Frequency range: 1.8 to 30 MHz continuous coverage
?Frequency counter accuracy: ?1 kHz across HF bands

?Capacitance range: 0 to 3926 pF nominal (256 values) on input side 0 to
976 pF nominal (64 values) on output side

?Inductance range: 0 to 24.28 ?H nominal (256 values)

I think their minimums are not realistic. I would not know how to
achieve 0pF with a 3926pF variable cap, for example. Also, why 3926
rather than 3900 or even 3920? It isn't all that easy to measure 6pF out
of 3920pF. I'm thinking that somebody just threw some numbers at the
spec sheet.

BUT! It is better than nothing and may help to make some reasonable
judgements.

The parts in a modern autotuner are not variable, they are a bunch of
fixed components switched in and out by relays.

The 3926 pF is the value of ALL the capacitors in parallel and 0 pF
would be a straight connection.



--
Jim Pennino

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

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.