W3JDR wrote:

Has anyone here built a GOOD antenna/network analyzer?

From what I can determine, the MFJ stuff doesn't resolve the sign of
reactances, nor does it have a computer interface. I was looking at Analog
Devices' AD8302 IC (http://www.analog.com) for this application. This is a
single-chip device that measures the gain and phase difference between 2 RF
inputs up to 2.7 GHZ with very high accuracy. It occurred to me that this
chip, together with a PIC that has A-D conversion, and a computer-controlled
station transceiver, could form the basis for a very nice programmable
antenna/network analyzer that would run rings around the MFJ units.

Comments?

Joe
W3JDR

Hi Joe,
Look at:
http://www.njqrp.org/antanal/
Perhaps your IC could be combined with this controller.

Dale W4OP

Dale,
Actually, I was thinking that the controller is a PC or laptop. It would
control the station transciever as a swept low-power frequency source, and
get the phase and gain readings from the PIC that would be paired with the
Analog Devices part (and of course a directional coupler of some sort...even
a simple bridge would suffice). This design could result in a very simple,
low-cost, and powerful vector network analyzer for the average ham.

Joe
W3JDR


"Dale Parfitt" wrote in message
...


W3JDR wrote:

Has anyone here built a GOOD antenna/network analyzer?

From what I can determine, the MFJ stuff doesn't resolve the sign of
reactances, nor does it have a computer interface. I was looking at
Analog
Devices' AD8302 IC (http://www.analog.com) for this application. This is
a
single-chip device that measures the gain and phase difference between 2
RF
inputs up to 2.7 GHZ with very high accuracy. It occurred to me that
this
chip, together with a PIC that has A-D conversion, and a
computer-controlled
station transceiver, could form the basis for a very nice programmable
antenna/network analyzer that would run rings around the MFJ units.

Comments?

Joe
W3JDR

Hi Joe,
Look at:
http://www.njqrp.org/antanal/
Perhaps your IC could be combined with this controller.

Dale W4OP

The chip you're looking at does have a 180 degree ambiguity unresolved.
Makes it tough to do the job you're asking of it. Wait a couple weeks and
look on Google for N2PK. You'll find a real vector network analyzer good
from 50 KHz to 60 MHz with narrow band application to 2 meters and 432 MHz.

W4ZCB

Harold,

The chip's phase measurement transer function has a positive slope for phase
angles less than 0deg and a negative slope for phase angles greater than
0deg. So it seems to me that resolving the 180 deg ambiguity is just a
matter of knowing which slope you're on. This might be done by switching in
a small known reactive component and observing which direction the phase
output changes. Once you know which slope you're on, I think you're home
free...no??

Joe
W3JDR
"Harold E. Johnson" wrote in message
news:Yhiab.496033$Ho3.84151@sccrnsc03...
The chip you're looking at does have a 180 degree ambiguity unresolved.
Makes it tough to do the job you're asking of it. Wait a couple weeks and
look on Google for N2PK. You'll find a real vector network analyzer good
from 50 KHz to 60 MHz with narrow band application to 2 meters and 432
MHz.

W4ZCB

The chip's phase measurement transer function has a positive slope for
phase
angles less than 0deg and a negative slope for phase angles greater than
0deg. So it seems to me that resolving the 180 deg ambiguity is just a
matter of knowing which slope you're on. This might be done by switching
in
a small known reactive component and observing which direction the phase
output changes. Once you know which slope you're on, I think you're home
free...no??

Do it the way you want to.

W4ZCB

Do it the way you want to.

Harold,
I'm puzzled by your reply. Does it mean that you agree, or that you
disagree, or that you're just brushing me off? If it's the latter, I can
accept that too...I'm just looking for a sincere dialog about an idea.

Joe
W3JDR

In article ,
says...
Do it the way you want to.

Harold,
I'm puzzled by your reply. Does it mean that you agree, or that you
disagree, or that you're just brushing me off? If it's the latter, I can
accept that too...I'm just looking for a sincere dialog about an idea.


Who knows what he meant by that, but the idea of using a "line
stretching" hack to resolve the phase ambiguity sounds like a great one
to me. I'd definitely be up for building a VNA that has decent
frequency coverage and that's PC-driven. I'll take a gander at the
AD8302's specs first chance I get and see how it looks!

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

I'm puzzled by your reply. Does it mean that you agree, or that you
disagree, or that you're just brushing me off? If it's the latter, I can
accept that too...I'm just looking for a sincere dialog about an idea.

Joe
W3JDR

I'm just brushing you off. I wrote to let you know of another avenue to do
the job you wish to do where someone else has invested a tremendous amount
of professional work in both the hardware and software. It will be available
on the Internet in a week or so. (Several of us have enjoyed the end product
as a Beta test group for something over a year.) I don't have any time or
interest in participating in a sincere dialog.

Regards

W4ZCB

In article ,
says...
Do it the way you want to.

Harold,
I'm puzzled by your reply. Does it mean that you agree, or that you
disagree, or that you're just brushing me off? If it's the latter, I can
accept that too...I'm just looking for a sincere dialog about an idea.


Who knows what he meant by that, but the idea of using a "line
stretching" hack to resolve the phase ambiguity sounds like a great one
to me. I'd definitely be up for building a VNA that has decent
frequency coverage and that's PC-driven. I'll take a gander at the
AD8302's specs first chance I get and see how it looks!

-- jm

------------------------------------------------------
http://www.qsl.net/ke5fx
Note: My E-mail address has been altered to avoid spam
------------------------------------------------------

I'm puzzled by your reply. Does it mean that you agree, or that you
disagree, or that you're just brushing me off? If it's the latter, I can
accept that too...I'm just looking for a sincere dialog about an idea.

Joe
W3JDR

I'm just brushing you off. I wrote to let you know of another avenue to do
the job you wish to do where someone else has invested a tremendous amount
of professional work in both the hardware and software. It will be available
on the Internet in a week or so. (Several of us have enjoyed the end product
as a Beta test group for something over a year.) I don't have any time or
interest in participating in a sincere dialog.

Regards

W4ZCB