MFJ259 conversion help
 

I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek

MFJ259 conversion help
 

"amdx" wrote in message
...
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek

Simple answer is you are wasting your time.

MFJ259 conversion help
 

On Tue, 03 Dec 2013 21:07:35 -0600, amdx wrote:

I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


Ever heard about OHM'S LAW?


w.

MFJ259 conversion help
 

On 12/4/2013 3:07 AM, Helmut Wabnig wrote:
On Tue, 03 Dec 2013 21:07:35 -0600, amdx wrote:

I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


Ever heard about OHM'S LAW?


w.


Yes Helmut I have. Obviously you don't have any understanding
of my question or you wouldn't have ask a smart ass question.
An MFJ259 is an antenna analyzer, it has two analog meters on it,
one displays the resistance of the load and the other the SWR.
Both meters have a non linear scale on the faceplate.

One would normally think a 50 ohm resistor would display a ratio
of 2 to 1 when compared to a 100 ohm resistor. As you can see the ratio
is 1.3 to 1. Also a 500 ohm and a 50 ohm resistor have a ratio of 10.
But the voltage ratio is 3.56.
So, do you have any other ideas?
Mikek

MFJ259 conversion help
 

On 12/3/2013 10:30 PM, Ralph Mowery wrote:
"amdx" wrote in message
...
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek

Simple answer is you are wasting your time.



Is that because you think MFJ is junk, or because
there is no easy relationship?

*&^%$# noticed I slipped the decimal point on the last few
measurements.
They should read,

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts
Sorry, Mikek

MFJ259 conversion help
 

On 12/4/2013 4:25 AM, amdx wrote:
On 12/4/2013 3:07 AM, Helmut Wabnig wrote:
On Tue, 03 Dec 2013 21:07:35 -0600, amdx wrote:

I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


Ever heard about OHM'S LAW?


w.


Yes Helmut I have. Obviously you don't have any understanding
of my question or you wouldn't have ask a smart ass question.
An MFJ259 is an antenna analyzer, it has two analog meters on it,
one displays the resistance of the load and the other the SWR.
Both meters have a non linear scale on the faceplate.

One would normally think a 50 ohm resistor would display a ratio
of 2 to 1 when compared to a 100 ohm resistor. As you can see the ratio
is 1.3 to 1. Also a 500 ohm and a 50 ohm resistor have a ratio of 10.
But the voltage ratio is 3.56.
So, do you have any other ideas?
Mikek

I noticed I slipped a decimal point on the last few measuements.


7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts
The last Ratio I posted as 3.56 to 1 should be 2.8 to 1.

MFJ259 conversion help
 

On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

MFJ259 conversion help
 

On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.0100 volts
365 0.0106 volts
498 0.0109 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

If you want it closer to your data, use the 4th order polynomial...

V = -5E-12*R^4 + 6E-09*R^3 - 3E-06*R^2 + 0.0007*R + 0.0334

MFJ259 conversion help
 

amdx wrote:
Is that because you think MFJ is junk, or because
there is no easy relationship?



It's a noise bridge. It works by putting a signal into an unknown tuned
circuit and looking for null points. If the antenna is not connected or
totally nonresonant, all of the signal coming out of the oscillator
goes to the meter. If it is totally resonant, it all goes out the antenna.

Before the MFJ, people used wide range noise generators, and receivers
tuned to the frequency you wanted to measure. You tuned the circut
to get a null in the receiver.

The more sophistocated ones had a variable resistance, you could adjust to
compensate for extra inductance or capacitance in the circuit.

How the impedance meter actually works I don't know, but I will hazzard a
guess. If you were to place a meter at the known resistance, you could get
an indication of impedance, possibly voltage, possibly current flow.

So what they do is calibrate the meter so that it reads 50 ohms at the
center, then place a 25 ohm load and read where the meter is. They do this
at several known resistances, and then make a meter scale. It is not a
precision instrument, so the same scale can be reproduced for the entire
production run.

It's only useful in context of the device it is in, and can't be used
for something else. Again a guess, but mine is that it is less than 10%
accurate (i.e. wider than 45ohms to 55 ohms reads 50 ohms).


Geoff.


--
Geoffrey S. Mendelson, N3OWJ/4X1GM/KBUH7245/KBUW5379

MFJ259 conversion help
 

On Wed, 04 Dec 2013 04:25:29 -0600, amdx wrote:


Ever heard about OHM'S LAW?


w.


Yes Helmut I have. Obviously you don't have any understanding
of my question or you wouldn't have ask a smart ass question.
An MFJ259 is an antenna analyzer, it has two analog meters on it,
one displays the resistance of the load and the other the SWR.
Both meters have a non linear scale on the faceplate.

One would normally think a 50 ohm resistor would display a ratio
of 2 to 1 when compared to a 100 ohm resistor. As you can see the ratio
is 1.3 to 1. Also a 500 ohm and a 50 ohm resistor have a ratio of 10.
But the voltage ratio is 3.56.
So, do you have any other ideas?
Mikek

Could it be you don't know how to calculate an SWR?
Then look at this:
https://sites.google.com/site/tapeme...wave-ratio-swr


w.

MFJ259 conversion help
 

On 12/4/2013 6:14 AM, Helmut Wabnig wrote:
On Wed, 04 Dec 2013 04:25:29 -0600, amdx wrote:


Ever heard about OHM'S LAW?


w.


Yes Helmut I have. Obviously you don't have any understanding
of my question or you wouldn't have ask a smart ass question.
An MFJ259 is an antenna analyzer, it has two analog meters on it,
one displays the resistance of the load and the other the SWR.
Both meters have a non linear scale on the faceplate.

One would normally think a 50 ohm resistor would display a ratio
of 2 to 1 when compared to a 100 ohm resistor. As you can see the ratio
is 1.3 to 1. Also a 500 ohm and a 50 ohm resistor have a ratio of 10.
But the voltage ratio is 3.56.
So, do you have any other ideas?
Mikek

Could it be you don't know how to calculate an SWR?
Then look at this:
https://sites.google.com/site/tapeme...wave-ratio-swr


w.

I haven't started with SWR yet.
I'm reading the voltage across the meter that displays the R of the
load. The analog meter is fairly accurate, but the distance between 0
and 50 is the same as the distance between 50 and 500. It makes reading
an R of 275 ohms difficult. I was just hoping I could put a digital
meter on the unit and be able to get a bit more detailed numbers. But,
alas, now that I have the voltage readings, the only way I know how to
make sense of them is a conversion chart.
If 50mv = 50 ohms and 100mv = 100 ohms this would make sense but the
voltage vs resistance is non linear.
Thanks, Mikek
chart.

MFJ259 conversion help
 

On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for me.

Mikek

MFJ259 conversion help
 

On 12/4/2013 8:48 AM, amdx wrote:
On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for me.

Mikek

Good. I can tell you how I accomplished it if you are interested.

MFJ259 conversion help
 

"amdx" wrote in message
...
Is that because you think MFJ is junk, or because
there is no easy relationship?


No it is not that I think the MFJ is junk, just there is no easy
relationship.

You did not mention if the volts were AC or DC or RF that I recall.

If DC there is no relationship at all. You do not use DC to measure the
inpedance of an antenna. If AC that most voltmeters will show, the
frequency range is too low to get a meaningful showing. If RF, you most
likely loose too much in the length of the leads.

What you are doing is sort of like sticking the probes in the side of a
tree and trying to see how tall that tree is. You see something on the
meter, but it does not help to tell how tall that tree is.

What you are doing while a learning experiance , is just a negative one.
One that does not work for anything. Like Tom Edison and the light bulb.
When he had tried about 60 differant things for the filiment of the bulb, he
said I now know 60 things that do not work.

MFJ259 conversion help
 

On Wed, 04 Dec 2013 08:39:56 -0600, amdx wrote:

On 12/4/2013 6:14 AM, Helmut Wabnig wrote:
On Wed, 04 Dec 2013 04:25:29 -0600, amdx wrote:


Ever heard about OHM'S LAW?


w.


Yes Helmut I have. Obviously you don't have any understanding
of my question or you wouldn't have ask a smart ass question.
An MFJ259 is an antenna analyzer, it has two analog meters on it,
one displays the resistance of the load and the other the SWR.
Both meters have a non linear scale on the faceplate.

One would normally think a 50 ohm resistor would display a ratio
of 2 to 1 when compared to a 100 ohm resistor. As you can see the ratio
is 1.3 to 1. Also a 500 ohm and a 50 ohm resistor have a ratio of 10.
But the voltage ratio is 3.56.
So, do you have any other ideas?
Mikek

Could it be you don't know how to calculate an SWR?
Then look at this:
https://sites.google.com/site/tapeme...wave-ratio-swr


w.

I haven't started with SWR yet.
I'm reading the voltage across the meter that displays the R of the
load. The analog meter is fairly accurate, but the distance between 0
and 50 is the same as the distance between 50 and 500. It makes reading
an R of 275 ohms difficult. I was just hoping I could put a digital
meter on the unit and be able to get a bit more detailed numbers. But,
alas, now that I have the voltage readings, the only way I know how to
make sense of them is a conversion chart.
If 50mv = 50 ohms and 100mv = 100 ohms this would make sense but the
voltage vs resistance is non linear.
Thanks, Mikek
chart.


Ah..now I think I understand

It looks like this:
http://img203.imageshack.us/img203/4766/863l.gif


w.

MFJ259 conversion help
 

On 12/4/2013 9:14 AM, John S wrote:
On 12/4/2013 8:48 AM, amdx wrote:
On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for me.

Mikek

Good. I can tell you how I accomplished it if you are interested.

Hi John S,
Please don't let me work you if your not interested, this is now
probably more of a curiosity than a way to make the MFJ259 more useful.
I ran all the numbers with the formula, it is not accurate enough to
me usable. I don't know if that is a calibration error, resistor error,
(I used 1% resistors) a me error, or the wrong formula.


I don't think it correlates very well with my measurements.
Might need to use fixed font to read this.

My Measurements.

Real R Calculated R Measured Voltage


7.5 ohms 11.4 0.0388 volts
15 15.3 0.0444 volts
25.5 18.3 0.0478 volts
39 30.7 0.0577 volts
50 37.3 0.0614 volts
100 102 0.0807 volts
140 158.9 0.0891 volts
174 200 0.0935 volts
221 253 0.0980 volts
249 284 0.1000 volts
365 384.6 0.1060 volts
498 457.4 0.1090 volts

This is really only usable at 100 ohms. Only 2% error.
52% error low end and 8.1% top end
Is there a better formula.
I'm trying to use a digital meter in place of basically a hand drawn
dial that is very nonlinear.
I'm wondering if I calibrated 50 ohms to read a bit lower
or higher voltage it might help

Anyone's helpful thoughts,
Thanks, Mike

MFJ259 conversion help
 

On 12/5/2013 4:13 AM, Helmut Wabnig wrote:
On Wed, 04 Dec 2013 08:39:56 -0600, amdx wrote:

On 12/4/2013 6:14 AM, Helmut Wabnig wrote:
On Wed, 04 Dec 2013 04:25:29 -0600, amdx wrote:


Ever heard about OHM'S LAW?


w.


Yes Helmut I have. Obviously you don't have any understanding
of my question or you wouldn't have ask a smart ass question.
An MFJ259 is an antenna analyzer, it has two analog meters on it,
one displays the resistance of the load and the other the SWR.
Both meters have a non linear scale on the faceplate.

One would normally think a 50 ohm resistor would display a ratio
of 2 to 1 when compared to a 100 ohm resistor. As you can see the ratio
is 1.3 to 1. Also a 500 ohm and a 50 ohm resistor have a ratio of 10.
But the voltage ratio is 3.56.
So, do you have any other ideas?
Mikek

Could it be you don't know how to calculate an SWR?
Then look at this:
https://sites.google.com/site/tapeme...wave-ratio-swr


w.

I haven't started with SWR yet.
I'm reading the voltage across the meter that displays the R of the
load. The analog meter is fairly accurate, but the distance between 0
and 50 is the same as the distance between 50 and 500. It makes reading
an R of 275 ohms difficult. I was just hoping I could put a digital
meter on the unit and be able to get a bit more detailed numbers. But,
alas, now that I have the voltage readings, the only way I know how to
make sense of them is a conversion chart.
If 50mv = 50 ohms and 100mv = 100 ohms this would make sense but the
voltage vs resistance is non linear.
Thanks, Mikek
chart.


Ah..now I think I understand

It looks like this:
http://img203.imageshack.us/img203/4766/863l.gif


w.

Yes! and this is one way I could handle this is to add more grid lines
and just use the graph to find R by finding were V crosses.
I posted new info using the formula John S developed, as you may read
the formula does not come out as accurate as I'd like, I'm not sure why.
Thanks for the interest, Mikek

MFJ259 conversion help
 

On 12/5/2013 10:26 AM, amdx wrote:
On 12/4/2013 9:14 AM, John S wrote:
On 12/4/2013 8:48 AM, amdx wrote:
On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for me.

Mikek

Good. I can tell you how I accomplished it if you are interested.

Hi John S,
Please don't let me work you if your not interested, this is now
probably more of a curiosity than a way to make the MFJ259 more useful.
I ran all the numbers with the formula, it is not accurate enough to
me usable. I don't know if that is a calibration error, resistor error,
(I used 1% resistors) a me error, or the wrong formula.


I don't think it correlates very well with my measurements.
Might need to use fixed font to read this.

My Measurements.

Real R Calculated R Measured Voltage


7.5 ohms 11.4 0.0388 volts
15 15.3 0.0444 volts
25.5 18.3 0.0478 volts
39 30.7 0.0577 volts
50 37.3 0.0614 volts
100 102 0.0807 volts
140 158.9 0.0891 volts
174 200 0.0935 volts
221 253 0.0980 volts
249 284 0.1000 volts
365 384.6 0.1060 volts
498 457.4 0.1090 volts

This is really only usable at 100 ohms. Only 2% error.
52% error low end and 8.1% top end
Is there a better formula.
I'm trying to use a digital meter in place of basically a hand drawn
dial that is very nonlinear.
I'm wondering if I calibrated 50 ohms to read a bit lower
or higher voltage it might help

Anyone's helpful thoughts,
Thanks, Mike

I was going to suggest you try the polynomial, but I just discovered
that Excel has lied grossly to me. The trend line shows it to match very
well. However, I used the equation Excel produces to calculate using the
original values and saw a 34% error at the high end not shown by the
trend line. This has nothing to do with your data. I will see if I can
determine the cause of this.

Cheers,
John

MFJ259 conversion help
 

On Thu, 05 Dec 2013 10:26:33 -0600, amdx wrote:

On 12/4/2013 9:14 AM, John S wrote:
On 12/4/2013 8:48 AM, amdx wrote:
On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for me.

Mikek

Good. I can tell you how I accomplished it if you are interested.

Hi John S,
Please don't let me work you if your not interested, this is now
probably more of a curiosity than a way to make the MFJ259 more useful.
I ran all the numbers with the formula, it is not accurate enough to
me usable. I don't know if that is a calibration error, resistor error,
(I used 1% resistors) a me error, or the wrong formula.


I don't think it correlates very well with my measurements.
Might need to use fixed font to read this.

My Measurements.

Real R Calculated R Measured Voltage


7.5 ohms 11.4 0.0388 volts
15 15.3 0.0444 volts
25.5 18.3 0.0478 volts
39 30.7 0.0577 volts
50 37.3 0.0614 volts
100 102 0.0807 volts
140 158.9 0.0891 volts
174 200 0.0935 volts
221 253 0.0980 volts
249 284 0.1000 volts
365 384.6 0.1060 volts
498 457.4 0.1090 volts

This is really only usable at 100 ohms. Only 2% error.
52% error low end and 8.1% top end
Is there a better formula.
I'm trying to use a digital meter in place of basically a hand drawn
dial that is very nonlinear.
I'm wondering if I calibrated 50 ohms to read a bit lower
or higher voltage it might help

Anyone's helpful thoughts,
Thanks, Mike



Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

MFJ259 conversion help
 

On 12/5/2013 11:31 AM, Helmut Wabnig wrote:
On Thu, 05 Dec 2013 10:26:33 -0600, amdx wrote:

On 12/4/2013 9:14 AM, John S wrote:
On 12/4/2013 8:48 AM, amdx wrote:
On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for me.

Mikek

Good. I can tell you how I accomplished it if you are interested.

Hi John S,
Please don't let me work you if your not interested, this is now
probably more of a curiosity than a way to make the MFJ259 more useful.
I ran all the numbers with the formula, it is not accurate enough to
me usable. I don't know if that is a calibration error, resistor error,
(I used 1% resistors) a me error, or the wrong formula.


I don't think it correlates very well with my measurements.
Might need to use fixed font to read this.

My Measurements.

Real R Calculated R Measured Voltage


7.5 ohms 11.4 0.0388 volts
15 15.3 0.0444 volts
25.5 18.3 0.0478 volts
39 30.7 0.0577 volts
50 37.3 0.0614 volts
100 102 0.0807 volts
140 158.9 0.0891 volts
174 200 0.0935 volts
221 253 0.0980 volts
249 284 0.1000 volts
365 384.6 0.1060 volts
498 457.4 0.1090 volts

This is really only usable at 100 ohms. Only 2% error.
52% error low end and 8.1% top end
Is there a better formula.
I'm trying to use a digital meter in place of basically a hand drawn
dial that is very nonlinear.
I'm wondering if I calibrated 50 ohms to read a bit lower
or higher voltage it might help

Anyone's helpful thoughts,
Thanks, Mike



Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

Yes, the trend line is very close. But, please perform a calculation on
the 498R value using the equation and let me know if it agrees. If yours
does, then something is wrong here.

Thanks,
John

MFJ259 conversion help
 

On 12/5/2013 1:49 PM, John S wrote:
On 12/5/2013 11:31 AM, Helmut Wabnig wrote:
On Thu, 05 Dec 2013 10:26:33 -0600, amdx wrote:

On 12/4/2013 9:14 AM, John S wrote:
On 12/4/2013 8:48 AM, amdx wrote:
On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for
me.

Mikek

Good. I can tell you how I accomplished it if you are interested.

Hi John S,
Please don't let me work you if your not interested, this is now
probably more of a curiosity than a way to make the MFJ259 more useful.
I ran all the numbers with the formula, it is not accurate enough to
me usable. I don't know if that is a calibration error, resistor error,
(I used 1% resistors) a me error, or the wrong formula.


I don't think it correlates very well with my measurements.
Might need to use fixed font to read this.

My Measurements.

Real R Calculated R Measured Voltage


7.5 ohms 11.4 0.0388 volts
15 15.3 0.0444 volts
25.5 18.3 0.0478 volts
39 30.7 0.0577 volts
50 37.3 0.0614 volts
100 102 0.0807 volts
140 158.9 0.0891 volts
174 200 0.0935 volts
221 253 0.0980 volts
249 284 0.1000 volts
365 384.6 0.1060 volts
498 457.4 0.1090 volts

This is really only usable at 100 ohms. Only 2% error.
52% error low end and 8.1% top end
Is there a better formula.
I'm trying to use a digital meter in place of basically a hand drawn
dial that is very nonlinear.
I'm wondering if I calibrated 50 ohms to read a bit lower
or higher voltage it might help

Anyone's helpful thoughts,
Thanks, Mike



Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

Yes, the trend line is very close. But, please perform a calculation on
the 498R value using the equation and let me know if it agrees. If yours
does, then something is wrong here.

Thanks,
John


Helmut -

Please see this. I think Excel is screwed up.

https://imageshack.com/i/mrg919p

MFJ259 conversion help
 

On Thu, 05 Dec 2013 14:42:02 -0600, John S
wrote:

On 12/5/2013 1:49 PM, John S wrote:

Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

Yes, the trend line is very close. But, please perform a calculation on
the 498R value using the equation and let me know if it agrees. If yours
does, then something is wrong here.

Thanks,
John


Helmut -

Please see this. I think Excel is screwed up.

https://imageshack.com/i/mrg919p


Yes, you are right.
Although EXCEL calculated the curve correctly in its own diagram,
it outputs false (rounded) parameters for the curve fitting polynom.
Compare with the Graphmatica plot, they are ident.
Have to find out tomorrow how to get the polynom factors without
rounding errors, if possible.
http://img834.imageshack.us/img834/8177/altv.gif

w.

MFJ259 conversion help
 

On 12/5/2013 11:31 AM, Helmut Wabnig wrote:
On Thu, 05 Dec 2013 10:26:33 -0600, amdx wrote:

On 12/4/2013 9:14 AM, John S wrote:
On 12/4/2013 8:48 AM, amdx wrote:
On 12/4/2013 4:50 AM, John S wrote:
On 12/3/2013 9:07 PM, amdx wrote:
I may be asking for something that doesn't have an answer.

I connected a voltmeter to the R meter of my MFJ259.
I checked a bunch of resistors and recorded the voltages.
Now I have all these voltage readings vs. Resistance and
don't know how to relate them except for a conversion graph.

Is there a math function that relates these voltages to Resistance?

Load Resistance Voltage reading

7.5 ohms 0.0388 volts
15 0.0444 volts
25.5 0.0478 volts
39 0.0577 volts
50 0.0614 volts
100 0.0807 volts
140 0.0891 volts
174 0.0935 volts
221 0.0980 volts
249 0.1000 volts
365 0.1060 volts
498 0.1090 volts

If you can figure this out, I'll reward you with the
SWR chart :-)

Thanks, Mikek


V = 0.0191*ln(R) - 0.0077

You're welcome.

Thanks, I'll learn about that and see if I can make it work for me.

Mikek

Good. I can tell you how I accomplished it if you are interested.

Hi John S,
Please don't let me work you if your not interested, this is now
probably more of a curiosity than a way to make the MFJ259 more useful.
I ran all the numbers with the formula, it is not accurate enough to
me usable. I don't know if that is a calibration error, resistor error,
(I used 1% resistors) a me error, or the wrong formula.


I don't think it correlates very well with my measurements.
Might need to use fixed font to read this.

My Measurements.

Real R Calculated R Measured Voltage


7.5 ohms 11.4 0.0388 volts
15 15.3 0.0444 volts
25.5 18.3 0.0478 volts
39 30.7 0.0577 volts
50 37.3 0.0614 volts
100 102 0.0807 volts
140 158.9 0.0891 volts
174 200 0.0935 volts
221 253 0.0980 volts
249 284 0.1000 volts
365 384.6 0.1060 volts
498 457.4 0.1090 volts

This is really only usable at 100 ohms. Only 2% error.
52% error low end and 8.1% top end
Is there a better formula.
I'm trying to use a digital meter in place of basically a hand drawn
dial that is very nonlinear.
I'm wondering if I calibrated 50 ohms to read a bit lower
or higher voltage it might help

Anyone's helpful thoughts,
Thanks, Mike



Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

FWIW, I measured a 549 ohm resistor and
the voltage was. 0.1105mv

Mikek

MFJ259 conversion help
 

On 12/4/2013 9:48 AM, Ralph Mowery wrote:
"amdx" wrote in message
...
Is that because you think MFJ is junk, or because
there is no easy relationship?


No it is not that I think the MFJ is junk, just there is no easy
relationship.

You did not mention if the volts were AC or DC or RF that I recall.

I'm reading DC volts across a DC meter.


If DC there is no relationship at all. You do not use DC to measure the
inpedance of an antenna. If AC that most voltmeters will show, the
frequency range is too low to get a meaningful showing. If RF, you most
likely loose too much in the length of the leads.


I'm using the MFJ259, you might want to get a little information about it.

What you are doing is sort of like sticking the probes in the side of a
tree and trying to see how tall that tree is. You see something on the
meter, but it does not help to tell how tall that tree is.

What you are doing while a learning experiance , is just a negative one.
One that does not work for anything. Like Tom Edison and the light bulb.
When he had tried about 60 differant things for the filiment of the bulb, he
said I now know 60 things that do not work.


Again, look up the MFJ259

Thanks, Mikek

MFJ259 conversion help
 

In article ,
Ralph Mowery wrote:

So you are using a DC meter . How do you expect to get any thing meaningful
out of it ?

If I understand correctly, the original poster has lightly modified an
MFJ259, and is "tapping out" the DC voltage which drives its internal
meter circuitry. This voltage is a function of the impedance being
calculated by the MFJ's RF-impedance-measurement circuit.

The original poster is *not* trying to use a DC meter to measure the
RF coming out of the MFJ's SO-239 port.

MFJ259 conversion help
 

"amdx" wrote in message
...
You still don't understand. Do you want to?
I'll post exactly what I'm doing if you want to know.
The simple answer, this antenna analyzer has to DC meters
that display R and SWR. I'm reading the voltage across one of those meters
with my meter set on DC 200mV scale.
Might help if Googled MFJ259 Schematic, don't get the 259B, not the
same.
Mikek

OK, It is my fault for not understanding where you were placing the meter.
I see now that you are just hooking across one of the meters on the MFJ to
get a more accurate measurment.

I thought you were placing it across the actual resistor hooked to the MFJ.

MFJ259 conversion help
 

On 12/5/2013 8:56 PM, Ralph Mowery wrote:
"amdx" wrote in message
...
You still don't understand. Do you want to?
I'll post exactly what I'm doing if you want to know.
The simple answer, this antenna analyzer has to DC meters
that display R and SWR. I'm reading the voltage across one of those meters
with my meter set on DC 200mV scale.
Might help if Googled MFJ259 Schematic, don't get the 259B, not the
same.
Mikek

OK, It is my fault for not understanding where you were placing the meter.
I see now that you are just hooking across one of the meters on the MFJ to
get a more accurate measurement.

I thought you were placing it across the actual resistor hooked to the MFJ.



Ahh, no problem, sometimes hard to explain things when details you
see as obvious may not be seen that way by others. Glad you got it,
but I'm still a bit lost. The Formula John S gave me was close but not
close enough. They are into a problem with excell now, don't know if
they will get back to me or not :-).

MFJ259 conversion help
 

On 12/5/2013 4:38 PM, Helmut Wabnig wrote:
On Thu, 05 Dec 2013 14:42:02 -0600, John S
wrote:

On 12/5/2013 1:49 PM, John S wrote:

Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

Yes, the trend line is very close. But, please perform a calculation on
the 498R value using the equation and let me know if it agrees. If yours
does, then something is wrong here.

Thanks,
John


Helmut -

Please see this. I think Excel is screwed up.

https://imageshack.com/i/mrg919p


Yes, you are right.
Although EXCEL calculated the curve correctly in its own diagram,
it outputs false (rounded) parameters for the curve fitting polynom.
Compare with the Graphmatica plot, they are ident.
Have to find out tomorrow how to get the polynom factors without
rounding errors, if possible.
http://img834.imageshack.us/img834/8177/altv.gif

w.


I found these coefficients at a site called ZunZun dot com:

y = a + bx + cx2 + dx3 + fx4 + gx5

Fitting target of lowest sum of squared absolute error =
7.0645972802275931E-06

a = 3.3214807109861584E-02
b = 7.2539508790925885E-04
c = -3.2830626216867792E-06
d = 7.9094355769986563E-09
f = -9.4574857953126017E-12
g = 4.3679252922923517E-15

Worst case error is .202% at 50.

John

MFJ259 conversion help
 

On Fri, 06 Dec 2013 03:57:40 -0600, John S
wrote:

On 12/5/2013 4:38 PM, Helmut Wabnig wrote:
On Thu, 05 Dec 2013 14:42:02 -0600, John S
wrote:

On 12/5/2013 1:49 PM, John S wrote:

Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

Yes, the trend line is very close. But, please perform a calculation on
the 498R value using the equation and let me know if it agrees. If yours
does, then something is wrong here.

Thanks,
John


Helmut -

Please see this. I think Excel is screwed up.

https://imageshack.com/i/mrg919p


Yes, you are right.
Although EXCEL calculated the curve correctly in its own diagram,
it outputs false (rounded) parameters for the curve fitting polynom.
Compare with the Graphmatica plot, they are ident.
Have to find out tomorrow how to get the polynom factors without
rounding errors, if possible.
http://img834.imageshack.us/img834/8177/altv.gif

w.


I found these coefficients at a site called ZunZun dot com:

y = a + bx + cx2 + dx3 + fx4 + gx5

Fitting target of lowest sum of squared absolute error =
7.0645972802275931E-06

a = 3.3214807109861584E-02
b = 7.2539508790925885E-04
c = -3.2830626216867792E-06
d = 7.9094355769986563E-09
f = -9.4574857953126017E-12
g = 4.3679252922923517E-15

Worst case error is .202% at 50.

John


Yes, that's better

neither EXCEL nor OPEN OFFICE can do it correctly.
Excel generates the correct formula, but outputs only truncated or
rounded coefficients.
I do not know how to access the internal correct coefficients
in Excel.

Then I found this site:
http://www.xuru.org/rt/PR.asp#CopyPaste
Which outputs the following:

http://img43.imageshack.us/img43/6194/jmph.jpg


Which gives the correct curve when inserted into EXCEL
with some editing.
=4,368089718E-15*(B4)^5-9,457445532E-12*(B4)^4+0,000000007909410217*(B4)^3-0,000003283056669*(B4)^2+0,0007253920186*(B4)+0,03 321499593
http://img547.imageshack.us/img547/1012/o8io.gif

To improve the curve fitting I suggest to take additional measurements
in the upper range.

w.

MFJ259 conversion help
 

On 12/6/2013 4:27 AM, Helmut Wabnig wrote:
On Fri, 06 Dec 2013 03:57:40 -0600, John S
wrote:

On 12/5/2013 4:38 PM, Helmut Wabnig wrote:
On Thu, 05 Dec 2013 14:42:02 -0600, John S
wrote:

On 12/5/2013 1:49 PM, John S wrote:

Well I did it using an old dirty trick:
adding one fake data point at the end to bend the curve.

http://img560.imageshack.us/img560/1845/yi2.gif

You must then not use the values
which are above the last valid data point.

You may program this formula into an Arduino .-)

w.

Yes, the trend line is very close. But, please perform a calculation on
the 498R value using the equation and let me know if it agrees. If yours
does, then something is wrong here.

Thanks,
John


Helmut -

Please see this. I think Excel is screwed up.

https://imageshack.com/i/mrg919p


Yes, you are right.
Although EXCEL calculated the curve correctly in its own diagram,
it outputs false (rounded) parameters for the curve fitting polynom.
Compare with the Graphmatica plot, they are ident.
Have to find out tomorrow how to get the polynom factors without
rounding errors, if possible.
http://img834.imageshack.us/img834/8177/altv.gif

w.


I found these coefficients at a site called ZunZun dot com:

y = a + bx + cx2 + dx3 + fx4 + gx5

Fitting target of lowest sum of squared absolute error =
7.0645972802275931E-06

a = 3.3214807109861584E-02
b = 7.2539508790925885E-04
c = -3.2830626216867792E-06
d = 7.9094355769986563E-09
f = -9.4574857953126017E-12
g = 4.3679252922923517E-15

Worst case error is .202% at 50.

John


Yes, that's better

neither EXCEL nor OPEN OFFICE can do it correctly.
Excel generates the correct formula, but outputs only truncated or
rounded coefficients.
I do not know how to access the internal correct coefficients
in Excel.

Then I found this site:
http://www.xuru.org/rt/PR.asp#CopyPaste
Which outputs the following:

http://img43.imageshack.us/img43/6194/jmph.jpg


Which gives the correct curve when inserted into EXCEL
with some editing.
=4,368089718E-15*(B4)^5-9,457445532E-12*(B4)^4+0,000000007909410217*(B4)^3-0,000003283056669*(B4)^2+0,0007253920186*(B4)+0,03 321499593
http://img547.imageshack.us/img547/1012/o8io.gif

To improve the curve fitting I suggest to take additional measurements
in the upper range.

w.


Together, I think we got a reasonable answer. Thanks for your
information. I did not know about adding an additional data point to
help the curve. Nice work.

MFJ259 conversion help
 

On 12/6/2013 1:52 AM, Jeff wrote:
Maybe I am missing something,and I don't have a MFJ259, but I assume
that the resistance reading is not a true resistance reading but Mod Z.
So any reactive part of the load will contribute to the reading. So when
used with a real antenna I am not sure why you would need such an
accurate readout, because Mod Z can have a resistive part that is well
away from the 'Resistance' reading on the meter.

73
Jeff

You are correct, Jeff. However, the exercise is to help him with
constructing an equation which relates his data points. It is his
decision to use the info or not.

I'm not trying to be nasty. I have just put blinder on myself to answer
only his direct question without offering better solutions (as if I had
any).

MFJ259 conversion help
 

On 12/6/2013 6:30 AM, John S wrote:
On 12/6/2013 1:52 AM, Jeff wrote:
Maybe I am missing something,and I don't have a MFJ259, but I assume
that the resistance reading is not a true resistance reading but Mod Z.
So any reactive part of the load will contribute to the reading. So when
used with a real antenna I am not sure why you would need such an
accurate readout, because Mod Z can have a resistive part that is well
away from the 'Resistance' reading on the meter.

73
Jeff

You are correct, Jeff. However, the exercise is to help him with
constructing an equation which relates his data points. It is his
decision to use the info or not.

I'm not trying to be nasty. I have just put blinder on myself to answer
only his direct question without offering better solutions (as if I had
any).

At a freq of 100 MHz I measured a 100 ohm resistor R = 100 SWR = 1.9
Then a 100 in series with 30pf (Xc=53 ohms) R = 85 SWR = 2.4
Then 100 ohms in parallel with 30pf R = 25 SWR = 6

This is not what I expected, so I've learned something.
I have equipment to measure up to 10 MHz, and I can measure
Q up to 50MHz.
I was hoping to use the MFJ259 to do something at higher frequencies.
I don't think this is the direction I should be looking.

Thanks for all your help, Mikek

MFJ259 conversion help
 

"amdx" wrote in message
...
).

At a freq of 100 MHz I measured a 100 ohm resistor R = 100 SWR = 1.9
Then a 100 in series with 30pf (Xc=53 ohms) R = 85 SWR = 2.4
Then 100 ohms in parallel with 30pf R = 25 SWR = 6

This is not what I expected, so I've learned something.
I have equipment to measure up to 10 MHz, and I can measure
Q up to 50MHz.
I was hoping to use the MFJ259 to do something at higher frequencies.
I don't think this is the direction I should be looking.


I am not sure what ou are trying so may be speaking out of turn again.

With the resistor and capacitors, have you tried adjusting the frequency for
the lowest SWR to see what the R value is at that frequency ?

MFJ259 conversion help
 

On 12/6/2013 11:31 AM, amdx wrote:
On 12/6/2013 6:30 AM, John S wrote:
On 12/6/2013 1:52 AM, Jeff wrote:
Maybe I am missing something,and I don't have a MFJ259, but I assume
that the resistance reading is not a true resistance reading but Mod Z.
So any reactive part of the load will contribute to the reading. So when
used with a real antenna I am not sure why you would need such an
accurate readout, because Mod Z can have a resistive part that is well
away from the 'Resistance' reading on the meter.

73
Jeff

You are correct, Jeff. However, the exercise is to help him with
constructing an equation which relates his data points. It is his
decision to use the info or not.

I'm not trying to be nasty. I have just put blinder on myself to answer
only his direct question without offering better solutions (as if I had
any).

At a freq of 100 MHz I measured a 100 ohm resistor R = 100 SWR = 1.9
Then a 100 in series with 30pf (Xc=53 ohms) R = 85 SWR = 2.4
Then 100 ohms in parallel with 30pf R = 25 SWR = 6

This is not what I expected, so I've learned something.
I have equipment to measure up to 10 MHz, and I can measure
Q up to 50MHz.
I was hoping to use the MFJ259 to do something at higher frequencies.
I don't think this is the direction I should be looking.

Thanks for all your help, Mikek


I'm not sure how the 259 is supposed to work, but I can supply the
theoretical values I think you should get.

100 R = 100 SWR = 2
100 + 30pF R = 100 SWR = 2.7
100||30pF R = 22 SWR = 4

Hope this helps.

MFJ259 conversion help
 

On 12/6/2013 4:34 PM, John S wrote:
On 12/6/2013 11:31 AM, amdx wrote:
On 12/6/2013 6:30 AM, John S wrote:
On 12/6/2013 1:52 AM, Jeff wrote:
Maybe I am missing something,and I don't have a MFJ259, but I assume
that the resistance reading is not a true resistance reading but Mod Z.
So any reactive part of the load will contribute to the reading. So
when
used with a real antenna I am not sure why you would need such an
accurate readout, because Mod Z can have a resistive part that is well
away from the 'Resistance' reading on the meter.

73
Jeff

You are correct, Jeff. However, the exercise is to help him with
constructing an equation which relates his data points. It is his
decision to use the info or not.

I'm not trying to be nasty. I have just put blinder on myself to answer
only his direct question without offering better solutions (as if I had
any).

At a freq of 100 MHz I measured a 100 ohm resistor R = 100 SWR = 1.9
Then a 100 in series with 30pf (Xc=53 ohms) R = 85 SWR = 2.4
Then 100 ohms in parallel with 30pf R = 25 SWR = 6

This is not what I expected, so I've learned something.
I have equipment to measure up to 10 MHz, and I can measure
Q up to 50MHz.
I was hoping to use the MFJ259 to do something at higher frequencies.
I don't think this is the direction I should be looking.

Thanks for all your help, Mikek


I'm not sure how the 259 is supposed to work, but I can supply the
theoretical values I think you should get.

100 R = 100 SWR = 2
100 + 30pF R = 100 SWR = 2.7
100||30pF R = 22 SWR = 4

Hope this helps.

At this point I've pretty much given up on the idea that this device
will do what I want, even with some mods.
Thanks, Mikek

MFJ259 conversion help
 

On 12/6/2013 8:07 PM, amdx wrote:
On 12/6/2013 4:34 PM, John S wrote:
On 12/6/2013 11:31 AM, amdx wrote:
On 12/6/2013 6:30 AM, John S wrote:
On 12/6/2013 1:52 AM, Jeff wrote:
Maybe I am missing something,and I don't have a MFJ259, but I assume
that the resistance reading is not a true resistance reading but
Mod Z.
So any reactive part of the load will contribute to the reading. So
when
used with a real antenna I am not sure why you would need such an
accurate readout, because Mod Z can have a resistive part that is well
away from the 'Resistance' reading on the meter.

73
Jeff

You are correct, Jeff. However, the exercise is to help him with
constructing an equation which relates his data points. It is his
decision to use the info or not.

I'm not trying to be nasty. I have just put blinder on myself to answer
only his direct question without offering better solutions (as if I had
any).

At a freq of 100 MHz I measured a 100 ohm resistor R = 100 SWR = 1.9
Then a 100 in series with 30pf (Xc=53 ohms) R = 85 SWR = 2.4
Then 100 ohms in parallel with 30pf R = 25 SWR = 6

This is not what I expected, so I've learned something.
I have equipment to measure up to 10 MHz, and I can measure
Q up to 50MHz.
I was hoping to use the MFJ259 to do something at higher frequencies.
I don't think this is the direction I should be looking.

Thanks for all your help, Mikek


I'm not sure how the 259 is supposed to work, but I can supply the
theoretical values I think you should get.

100 R = 100 SWR = 2
100 + 30pF R = 100 SWR = 2.7
100||30pF R = 22 SWR = 4

Hope this helps.

At this point I've pretty much given up on the idea that this device
will do what I want, even with some mods.
Thanks, Mikek

Do you know about VK1OD's Web site? It is full of information concerning
measurements, antennas, etc. I think I remember something about the 259.
You can just dig around and get a great education in RF. And he has lots
of calculator for RF stuff. That's where I learned a lot. Here is the
link...

http://www.vk1od.net/

Good luck.

John

MFJ259 conversion help
 

On 12/11/2013 11:24 AM, Jim Higgins wrote:
On Thu, 05 Dec 2013 19:21:13 -0600, in ,
amdx wrote:

On 12/5/2013 6:45 PM, Ralph Mowery wrote:

As I said, what you are doing is a waste of time.


You still don't understand. Do you want to?
I'll post exactly what I'm doing if you want to know.
The simple answer, this antenna analyzer has to DC meters
that display R and SWR. I'm reading the voltage across one of those
meters with my meter set on DC 200mV scale.
Might help if Googled MFJ259 Schematic, don't get the 259B, not the same.
Mikek


I think we've passed the point of no return here... where the OP is no
worse off than he was to start with, but now it's all our fault.


No, it's not "all our fault"
Ralph, did not have any knowledge of the workings of an MFJ259.
Once he had some 259 understanding, how I was hooking my meter made
sense to him.
This was a useful exercise for me, not so much for you.
Tell me a reason you gave your input, other than your boring life.
Mikek