Help with MFJ Antenna Analyzr
 

This post may be a bit OT, but I believe this is the forum where I can =
get some useful information.

I have an MFJ-259B antenna analyzer which works fine. I also have an =
MFJ-269 (the one also working on UHF) which instead gives me odd results =
on the HF bands.

I then sent the 269 back to MFJ for warranty repair, and when it came =
back it had exactly the same problem, despite I gave them a very =
detailed explanation of the problem.

In summary the problem is the following:

- loading the MFJ-269 with 50 ohm all is OK (it gives R=3D50, X=3D0)
- loading it with a different value, say a small 200 ohm carbon resistor =
with very short leads, it gives R=3D200, X=3D0 at around 10 MHz but, =
LOWERING the frequency (e.g. down to 3.5 MHz), it progressively shows an =
higher and higher X value. This result is clearly wrong as a resistor =
having 0 reactance at 10 MHz cannot show reactance at 3.5 MHz. This is =
confirmed by the the fact the MFJ-259 loaded with the same resistor =
shows X=3D0 at 3.5 MHz! So, no question about that!

Interesting to note that the MFJ-269 Product Review on QST magazine (May =
2005 issue, Table 3) shows EXACTLY the same problem! A 269 design =
problem which does not exist in the 259?

Reading the MFJ-269 factory calibration procedure (I have a copy of it), =
they instruct the operator to adjust the instrument at 10 MHz. And at 10 =
MHz it works fine!=20

Has anyone carried out a similar test?

Thanks & 73

Tony I0JX (also K0JX when in the US)

I did some playing with mine after getting it, but didn't see anything like
this. I did pretty much the same things, as I recall.

HOWEVER, I did notice that going into the advanced mode and setting it for
ZO of 75 ohms that is didn't report SWR correctly (should be 1:1 w/75 ohms
attached and it still said 1.5 as though it still was thinking 50 ohms). I
called and the "tech" who answered clearly didn't understand (said return
it) and I elected to drop it since it worked ok otherwise.


I'll try to find some time to re-check this issue.

73, Steve, K9DCI


"Antonio Vernucci" wrote in message
...
This post may be a bit OT, but I believe this is the forum where I can get
some useful information.

I have an MFJ-259B antenna analyzer which works fine. I also have an MFJ-269
(the one also working on UHF) which instead gives me odd results on the HF
bands.

I then sent the 269 back to MFJ for warranty repair, and when it came back
it had exactly the same problem, despite I gave them a very detailed
explanation of the problem.

In summary the problem is the following:

- loading the MFJ-269 with 50 ohm all is OK (it gives R=50, X=0)
- loading it with a different value, say a small 200 ohm carbon resistor
with very short leads, it gives R=200, X=0 at around 10 MHz but, LOWERING
the frequency (e.g. down to 3.5 MHz), it progressively shows an higher and
higher X value. This result is clearly wrong as a resistor having 0
reactance at 10 MHz cannot show reactance at 3.5 MHz. This is confirmed by
the the fact the MFJ-259 loaded with the same resistor shows X=0 at 3.5 MHz!
So, no question about that!

Interesting to note that the MFJ-269 Product Review on QST magazine (May
2005 issue, Table 3) shows EXACTLY the same problem! A 269 design problem
which does not exist in the 259?

Reading the MFJ-269 factory calibration procedure (I have a copy of it),
they instruct the operator to adjust the instrument at 10 MHz. And at 10 MHz
it works fine!

Has anyone carried out a similar test?

Thanks & 73

Tony I0JX (also K0JX when in the US)

Steve,

from what you write I presume you have the 269, not the 259B (which =
works fine).

As you are the only person who answered me, if you have time could you =
please re- check your 269 by loading it with a resistor in the range 150 =
to 200 ohm, verifying that the reactance (X) indication remains nearly =
zero when varying frequency in range 2 to 10 MHz.

The only 269s I know are mine and the one tested by ARRL on QST. And =
both of them have a problem. So, if yours does not show that problem, =
then I have some hope

73

Tony I0JX


"Steve Nosko" ha scritto nel =
messaggio ...
I did some playing with mine after getting it, but didn't see anything =
like
this. I did pretty much the same things, as I recall.
=20
HOWEVER, I did notice that going into the advanced mode and setting it =
for
ZO of 75 ohms that is didn't report SWR correctly (should be 1:1 w/75 =
ohms
attached and it still said 1.5 as though it still was thinking 50 =
ohms). I
called and the "tech" who answered clearly didn't understand (said =
return
it) and I elected to drop it since it worked ok otherwise.
=20
=20
I'll try to find some time to re-check this issue.
=20
73, Steve, K9DCI
=20
=20
"Antonio Vernucci" wrote in message
...
This post may be a bit OT, but I believe this is the forum where I can =
get
some useful information.
=20
I have an MFJ-259B antenna analyzer which works fine. I also have an =
MFJ-269
(the one also working on UHF) which instead gives me odd results on =
the HF
bands.
=20
I then sent the 269 back to MFJ for warranty repair, and when it came =
back
it had exactly the same problem, despite I gave them a very detailed
explanation of the problem.
=20
In summary the problem is the following:
=20
- loading the MFJ-269 with 50 ohm all is OK (it gives R=3D50, X=3D0)
- loading it with a different value, say a small 200 ohm carbon =
resistor
with very short leads, it gives R=3D200, X=3D0 at around 10 MHz but, =
LOWERING
the frequency (e.g. down to 3.5 MHz), it progressively shows an higher =
and
higher X value. This result is clearly wrong as a resistor having 0
reactance at 10 MHz cannot show reactance at 3.5 MHz. This is =
confirmed by
the the fact the MFJ-259 loaded with the same resistor shows X=3D0 at =
3.5 MHz!
So, no question about that!
=20
Interesting to note that the MFJ-269 Product Review on QST magazine =
(May
2005 issue, Table 3) shows EXACTLY the same problem! A 269 design =
problem
which does not exist in the 259?
=20
Reading the MFJ-269 factory calibration procedure (I have a copy of =
it),
they instruct the operator to adjust the instrument at 10 MHz. And at =
10 MHz
it works fine!
=20
Has anyone carried out a similar test?
=20
Thanks & 73
=20
Tony I0JX (also K0JX when in the US)
=20
=20

Help with MFJ Antenna Analyzr
 

Roger doger Antonio.

Guess I _didn't_ really look @ this back when I got it. SO...I did two
things with the same problem showing up. I even remember looking over the
QST comparisons and seeing some of the modles WORSE than the MFJ, but now
that I think of it I don't remember fi it was the 259 or the 296 they tested
nor so long ago. I probably figured they were the same bridge...


I used Huber Suhner 50 ohm loads (really good 50 ohm loads).

From 1.4 to 70 MhZ ( just flipped the 269 range switch) they show 49-51 ohms
and not more than 1-2 ohms X. All in the series representation (Rs + Xs)
Put 4 in parallel for a good 12.5 ohm load and at 4 and 1.9 I see 3-4 ohms
of X. this is 25% of R !!

Then, I got an old 1/4 W. carbon comp 180 ohm resistor. At 10 it showed
quite close to 180 ohms. I believe it was 176 and around 25 ohms X However
it showed up to 70-some ohms of X at 4 AND 1.9 MHz (same at both
frequencies). Again around 25% of R.

Being an RF electrical Engineer, I never expected this thing to be right on.
I only figures it would get me in the right direction and let me know when I
was in a "relatively small" 50 ohm circle. However, you are right. This
seems to be quite poor. You'd think you'd see poorer accuracy higher in
freq.

73, Steve, K,9'D;C.I


"Antonio Vernucci" wrote in message
...
Steve,

from what you write I presume you have the 269, not the 259B (which works
fine).

As you are the only person who answered me, if you have time could you
please re- check your 269 by loading it with a resistor in the range 150 to
200 ohm, verifying that the reactance (X) indication remains nearly zero
when varying frequency in range 2 to 10 MHz.

The only 269s I know are mine and the one tested by ARRL on QST. And both of
them have a problem. So, if yours does not show that problem, then I have
some hope

73

Tony I0JX


"Steve Nosko" ha scritto nel messaggio
...
I did some playing with mine after getting it, but didn't see anything
like
this. I did pretty much the same things, as I recall.

HOWEVER, I did notice that going into the advanced mode and setting it for
ZO of 75 ohms that is didn't report SWR correctly (should be 1:1 w/75 ohms
attached and it still said 1.5 as though it still was thinking 50 ohms).
I
called and the "tech" who answered clearly didn't understand (said return
it) and I elected to drop it since it worked ok otherwise.


I'll try to find some time to re-check this issue.

73, Steve, K9DCI


"Antonio Vernucci" wrote in message
...
This post may be a bit OT, but I believe this is the forum where I can get
some useful information.

I have an MFJ-259B antenna analyzer which works fine. I also have an
MFJ-269
(the one also working on UHF) which instead gives me odd results on the HF
bands.

I then sent the 269 back to MFJ for warranty repair, and when it came back
it had exactly the same problem, despite I gave them a very detailed
explanation of the problem.

In summary the problem is the following:

- loading the MFJ-269 with 50 ohm all is OK (it gives R=50, X=0)
- loading it with a different value, say a small 200 ohm carbon resistor
with very short leads, it gives R=200, X=0 at around 10 MHz but, LOWERING
the frequency (e.g. down to 3.5 MHz), it progressively shows an higher and
higher X value. This result is clearly wrong as a resistor having 0
reactance at 10 MHz cannot show reactance at 3.5 MHz. This is confirmed by
the the fact the MFJ-259 loaded with the same resistor shows X=0 at 3.5
MHz!
So, no question about that!

Interesting to note that the MFJ-269 Product Review on QST magazine (May
2005 issue, Table 3) shows EXACTLY the same problem! A 269 design problem
which does not exist in the 259?

Reading the MFJ-269 factory calibration procedure (I have a copy of it),
they instruct the operator to adjust the instrument at 10 MHz. And at 10
MHz
it works fine!

Has anyone carried out a similar test?

Thanks & 73

Tony I0JX (also K0JX when in the US)