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

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 technology has been available for several years to enable a manufacturer
to produce a reasonably priced, small, hand-held, battery-operated, antenna
analyser which displays the sign of jX.

But the manufacturers have not yet extracted all that's available from the
market. Its too early to introduce a new model which would outclass the old.

What is needed in the market is a new manufacturer who has no history to
take advantage of.

Chinese ?

Reg,
I don't think it has much to do with planned product lifecycle...it's just
inertia and complacency. Nor do I don't think there's enough volume for a
"Chinese" manufacturer.

I think the main reason we haven't seen something better is that it's too
small a market for a startup to tackle. It's definitely a product for a tiny
company.

Joe
W3JDR

"Reg Edwards" wrote in message
...
The technology has been available for several years to enable a
manufacturer
to produce a reasonably priced, small, hand-held, battery-operated,
antenna
analyser which displays the sign of jX.

But the manufacturers have not yet extracted all that's available from the
market. Its too early to introduce a new model which would outclass the
old.

What is needed in the market is a new manufacturer who has no history to
take advantage of.

Chinese ?

Reg,
I don't think it has much to do with planned product lifecycle...it's just
inertia and complacency. Nor do I don't think there's enough volume for a
"Chinese" manufacturer.

I think the main reason we haven't seen something better is that it's too
small a market for a startup to tackle. It's definitely a product for a tiny
company.

Joe
W3JDR

"Reg Edwards" wrote in message
...
The technology has been available for several years to enable a
manufacturer
to produce a reasonably priced, small, hand-held, battery-operated,
antenna
analyser which displays the sign of jX.

But the manufacturers have not yet extracted all that's available from the
market. Its too early to introduce a new model which would outclass the
old.

What is needed in the market is a new manufacturer who has no history to
take advantage of.

Chinese ?

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 technology has been available for several years to enable a manufacturer
to produce a reasonably priced, small, hand-held, battery-operated, antenna
analyser which displays the sign of jX.

But the manufacturers have not yet extracted all that's available from the
market. Its too early to introduce a new model which would outclass the old.

What is needed in the market is a new manufacturer who has no history to
take advantage of.

Chinese ?

All the analyzers I have considered have always been to inaccurate. They
sure may work on the DC bands below 30MHz where people think an
antenna is good if the SWR is below 3.

This IC seem promising. Together with a small MCU and AD and some flash
memory you might be able to build a really good instrument that could
beat everything on the market.

Does anyone know a source for these chipts whithin the EU? I have some
directional couplers without detectors that could easily be combined
with this chip.

Your Idea to use a PC to control the radio as a source seem interesting.
The only drawback would be the size of all the stuff you need to bring
into the garden when measuring.

Perhaps a modular design.
a) Optional RF-circuit (directional couplers) different for different
bands to increase accuracy.
b) Detector device (AD-chip, small controller with calibration data)
c) Optional display for computerless operation
d) Optional signal source for rig-less operation.

/Leif

Leif,

Does anyone know a source for these chipts whithin the EU?
I believe you can purchase them from the Analog Devices Web site. Don't know
if that works outside the US though.

I have some directional couplers without detectors that could easily be
combined with this chip.
Do you really need a directional coupler? How about just driving the load
through a known resistor
and measuring the voltage & phase shift across the unknown?

Your idea to use a PC to control the radio as a source seem interesting.
The only drawback would be the size
of all the stuff you need to bring into the garden when measuring.


I suggested the station rig as a source because it already has a
programmable frequency generator for any frequency the ham is likely
to need to measure...why reinvent it? On the other hand, it's easy these
days to build a DDS frequency source that works into the VHF range.
Used laptop PC's are plentiful and cheap, and have great computational and
display facilities. I was thinking of a small module that works
with the station PC or a laptop.

Joe
W3JDR

Leif,

Does anyone know a source for these chipts whithin the EU?
I believe you can purchase them from the Analog Devices Web site. Don't know
if that works outside the US though.

I have some directional couplers without detectors that could easily be
combined with this chip.
Do you really need a directional coupler? How about just driving the load
through a known resistor
and measuring the voltage & phase shift across the unknown?

Your idea to use a PC to control the radio as a source seem interesting.
The only drawback would be the size
of all the stuff you need to bring into the garden when measuring.


I suggested the station rig as a source because it already has a
programmable frequency generator for any frequency the ham is likely
to need to measure...why reinvent it? On the other hand, it's easy these
days to build a DDS frequency source that works into the VHF range.
Used laptop PC's are plentiful and cheap, and have great computational and
display facilities. I was thinking of a small module that works
with the station PC or a laptop.

Joe
W3JDR