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