"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

wrote in message
...
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.
Hello
You are absolutely right in fact a perfect ferrite transformer would be
better.
But an aerial must have a real impedance part to be of any use :-)
Specifications must be easy to verify.
Here it is the case.
How do you check the 0.1dB noise figure advocated by many LNB's ?
:-)

bilou wrote:

wrote in message
...
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.
Hello
You are absolutely right in fact a perfect ferrite transformer would be
better.

It is rather difficult for a ferrite transformer to convert a random
complex impedance to approximately 50 Ohm resistive, which is what
an autotuner does.

But an aerial must have a real impedance part to be of any use :-)

Which is why one uses an autotuner to convert the random complex impedance
to approximately 50 Ohm resistive.

Specifications must be easy to verify.

And life must be fair...

Here it is the case.
How do you check the 0.1dB noise figure advocated by many LNB's ?

With test equipment.


--
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.

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?

"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.

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?

My yard is very difficult for getting antennas up. I currently use a
vertical on 20-10 that is mounted on top of a rather large metal patio
cover.
The cover does have AC voltage available for patio lights/fans/bird bath
pump and such. So I could power a remote tuner separate from the coax if
required.

The current antenna for 20-10 is a 14.5 foot vertical, fed with a short run
of good coax and tuned at the rig end of the coax.

IIRC, the swr is about 6:1 on 20 meters, dips around 18 MHz and rises to
about 20:1 on 10 meters.
For 20:1 the charts say I will lose not more than 3 db with the short run of
coax, which is acceptable.

In practice, the antenna is performing well enough for me to leave it alone.
.....but you know how hams are.....

On 8/10/2015 8:30 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.

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?

My yard is very difficult for getting antennas up. I currently use a
vertical on 20-10 that is mounted on top of a rather large metal patio
cover.
The cover does have AC voltage available for patio lights/fans/bird bath
pump and such. So I could power a remote tuner separate from the coax
if required.

The current antenna for 20-10 is a 14.5 foot vertical, fed with a short
run of good coax and tuned at the rig end of the coax.

IIRC, the swr is about 6:1 on 20 meters, dips around 18 MHz and rises to
about 20:1 on 10 meters.
For 20:1 the charts say I will lose not more than 3 db with the short
run of coax, which is acceptable.

In practice, the antenna is performing well enough for me to leave it
alone. ....but you know how hams are.....

I remember now. I even made an EZNEC model (including your metal patio)
and got results for all the ham bands. Using the specs for the
MFJ-998RT, it seems that it may match all but the 1.8MHz band IF the
specs can be relied upon.

I don't want to encourage you to spend a lot of money based on my input.
I just had fun doing the modelling.

"John S" wrote in message ...

On 8/10/2015 8:30 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.

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?

My yard is very difficult for getting antennas up. I currently use a
vertical on 20-10 that is mounted on top of a rather large metal patio
cover.
The cover does have AC voltage available for patio lights/fans/bird bath
pump and such. So I could power a remote tuner separate from the coax
if required.

The current antenna for 20-10 is a 14.5 foot vertical, fed with a short
run of good coax and tuned at the rig end of the coax.

IIRC, the swr is about 6:1 on 20 meters, dips around 18 MHz and rises to
about 20:1 on 10 meters.
For 20:1 the charts say I will lose not more than 3 db with the short
run of coax, which is acceptable.

In practice, the antenna is performing well enough for me to leave it
alone. ....but you know how hams are.....

# I remember now. I even made an EZNEC model (including your metal patio)
# and got results for all the ham bands. Using the specs for the
# MFJ-998RT, it seems that it may match all but the 1.8MHz band IF the
# specs can be relied upon.

# I don't want to encourage you to spend a lot of money based on my input.
# I just had fun doing the modelling.

That's what money is for...to buy toys. Nowadays for me, that means radio
gear, cameras or guns

Wayne wrote:


"John S" wrote in message ...

On 8/10/2015 8:30 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.

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?

My yard is very difficult for getting antennas up. I currently use a
vertical on 20-10 that is mounted on top of a rather large metal patio
cover.
The cover does have AC voltage available for patio lights/fans/bird bath
pump and such. So I could power a remote tuner separate from the coax
if required.

The current antenna for 20-10 is a 14.5 foot vertical, fed with a short
run of good coax and tuned at the rig end of the coax.

IIRC, the swr is about 6:1 on 20 meters, dips around 18 MHz and rises to
about 20:1 on 10 meters.
For 20:1 the charts say I will lose not more than 3 db with the short
run of coax, which is acceptable.

In practice, the antenna is performing well enough for me to leave it
alone. ....but you know how hams are.....

# I remember now. I even made an EZNEC model (including your metal patio)
# and got results for all the ham bands. Using the specs for the
# MFJ-998RT, it seems that it may match all but the 1.8MHz band IF the
# specs can be relied upon.

# I don't want to encourage you to spend a lot of money based on my input.
# I just had fun doing the modelling.

That's what money is for...to buy toys. Nowadays for me, that means
radio gear, cameras or guns


Hams substitute the word 'necessities' for 'Toys'! :-)

Irv VE6BP

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