Antenna Analyzer Smith Chart

[flintstone mop]

Hello AM guys and Gals

I was wondering what value an antenna analyzer with a Smith Chart readout would have? I'm gonna guess that it could be a more effective tool than the analyzers we're used to using now.
The Smith Chart is the "Tell All" of what is really going on in an antenna system?

Fred

[W1ITT]

Fred..
For over 30 years I have run around the world working on HF phased arrays and Medium Wave arrays of various sorts.  A vector analyzer with Smith Chart presentation makes life easier.  If you are doing matching calculations, the phase and magnitude of the reflection coefficient is what you need.  But don't be intimidated as a purely visual approach while adjusting your adjustables will allow you to "walk" the match right in.
Aside from antenna work you can tune networks in transmitters.  A few years ago in one of the nations founded by "Stan", I pretuned the output stage of a 300 kw transmitter by calculating the plate load impedance, putting a resistor of that value from plate to ground, and walked in the output tuning, looking backwards into the cold transmitter) on a list of assigned frequencies.  When bringing up a big rig, without pretune data available, it saves a lot of work and maybe tubes and components.  With a two-port analyzer, you can tune filters and see their bandwidth, or cutoff characteristics.
I like my HP8714C that went for over $20K a few years ago, but on a trip last month to southeast Asia, I took my Array Solutions VNA2180 (about $1K) and it did the job well, and rode in my carry-on  bag, as opposed to the 99 pound Pelican case for the HP.  MFJ is selling a pocket sized analyzer for around $300 that is made in Asia and marked for them.  My friend Bob, W1GWU, has one and it works well.  Whatever you get, look for at least 0dbm source power to compete well with the neighborhood RF.
As an aside, I used to do a lot of graphical calculations on the Smith Chart.  Getting low on supplies, I called the company to order more and the fellow asked me what I was doing with "his" charts.  I told him, and he suggested a couple shortcuts.  Finally it dawned on me that he was Philip Smith, in his 80s by then, and he admitted that he sometimes hung around the office.  He was a real gentleman, generous with information and a very capable engineer.  We had a great chat.  His work made life easier for generations of engineers.
I started off with a GR916 impedance bridge, and you can work without a Smith Chart device, but as inexpensive as they are nowadays, they are worth having if you like to do much antenna work.  They spoil you, and I'd hate to work without one now, even on my amateur radio projects.  Tomorrow I'm taking the HP up to W1IMD's big tower in Hiram ,Maine to adjust the reflector on his 160 meter (fixed) cubical quad.  Good clean fun!
73 de W1ITT

[M0VRF]

Yes, a Vector NETWORK ANALYSER!

Most useful and the centre of any RF lab.

Impedance matching, filter plots, VSWR, it's all there

HP  8712 is a good ol' instrument, $2k?

For any antenna work just look at the 'Return loss' (or VSWR) and waggle things around till you get the results you want.

You can see the match and B/W in one go then flip over to 'Smith' to see why the heck it's not working!

J.

[WA2SQQ]

Smith charts and complex impedance is a topic that has confused me since day 1. I enjoy experimenting with antennas, and much of what I've done had to be discovered by trial and error. I've read several article, and I've been able to grasp some of it but there are still too many gaps. Does anyone know of some on line content, "Smith Charts and Complex Impedance for Dummies"?

[flintstone mop]

I'm a little in the dark too. I'm thinking a Smith Chart will show which way to go, to get rid of the offending reactance. Most analyzers will indicate a reactance, but you have to guess. Capacitive or inductive reactance?
The Smith Chart seems like it would be valuable in antenna experimentation, or building a new antenna. The low SWR is not always a sign of an efficient antenna.

[W1ITT]

http://www.antenna-theory.com/tutorial/smith/chart.php

The above is a pretty good Smith Chart set of lessons, no more mathmatical than it needs to be. 
But if that is intimidating, you can use the Smith Chart visually and intuitively.  If you calibrated to a 50 ohm load, and 50 ohms is your desired match impedance, then all you really have to know is that the center of the chart is "good" and the rest is not so good, and the perimeter of the chart is stinko.  Just crank on your tuner knob and see what way the marker dot moves at your frequency of interest.  Then crank on the other knob and see what happens there.  Usually, the plots run on arcs across the chart and usually at cross directions to each other.  By diddling the knobs, you can walk it right in.  You can also see the effect of the interaction of the controls, which takes even more mystery out of the process.  I have, in the past, showed nontechnical customers how to tune in a matching circuit in a simple system.  The pencil pusher types love doing it themselves when everything is staged well for them. 
Tuning a gamma match, or a dipole by adjusting both the length and height or slant of an inverted V can all be done intuitively.  Looking "backwards" in the output network of a cold transmitter works well too.  This is not to say that we should all adopt the "push the button, get a banana" methods and avoid real learning, but if one is not fully progressed on his educational journey it can be helpful to get practical as well as theoretical education in the same time frame.  Done at the same time, this stuff all starts to make sense.
By the way, the antenna analyzer that my friend W1GWU has is the MFJ 226.  Again, it's made in the far east and labeled for them, and it looks to be a very capable unit, and quite affordable for all that it does.
If I didn't already have three network analyzers, a vector voltmeter and an impedance bridge, I'd think seriously of having one.  Some dealers sell them for less than the list price.

By the way, it doesn't have anything on Smith Charts, but the new Antenna Physics, by Zavrel, published by ARRL is a pretty good book to understand the how and why of antennas.  There is not a single dimensioned antenna in it as that's all covered in the Antenna Book, but it takes the electromagnetics back to physics and develops the concepts.  I wish I'd had this as a freshman in college, as he does a good job of tying theory and practice together, which makes understanding the concepts easier.    Many of the ARRL books seem like rehashes of QST articles, but this one stands on it's own and is worth having as a refresher, or as part of an early technical education.

[W3RSW]

https://www.gigaparts.com/1-230MHz-Graphical-Antenna-Impedance-Analyzer.html/

Here you go Mopster!
What a machine he's mentioned, Intuitive and easy operation for most purposes. Make sure you look at the review video in full screen, further down the Gigaparts sales page.  The reviewer does a nice hands on job showing the essentials.
Tha Asian made MFJ 226 does a lot in a portable, pretty rugged package.

Thought I'd never need an analyzer but the progress, capability and dropping price/performance ratio of these gadgets is going to push me over the edge.  

[flintstone mop]

I have performed the analyzer back into a "cold" transmitter, that was modified for multi-band operation. A McMartin BA 1K. 160 meters to 40 meters. Took notes on the settings and the transmitter performed perfectly on those bands, with some minor tweeks, at operating voltages. Disconnected the the tube plate caps and substituted a resistor close to the impedance of the tubes.
During the heyday of KC4MOP and a basement full of B'cast transmitters.
Regret getting rid of all those nice transmitters.

[KA6MOK]

Smith charts and complex impedance is a topic that has confused me since day 1. I enjoy experimenting with antennas, and much of what I've done had to be discovered by trial and error. I've read several article, and I've been able to grasp some of it but there are still too many gaps. Does anyone know of some on line content, "Smith Charts and Complex Impedance for Dummies"?

Here's a great program for playing around with filters/matching networks and the Smith Chart:
http://ae6ty.com/Smith_Charts.html   Nothing like being able to play around with actual (well, virtual) parts and seeing the result, to get a feel for it. It's really a network simulator with a really good Smith Chart display attached to it.  There's a few instruction videos, which IFIRC, were very good at explaining the basics, and more advanced stuff.  I used it at a workplace to teach people what all was going on in that black magic RF domain... You can basically do the playing around that W1ITT is suggesting, without buying the analyzer first...  

By the way,  extremely cool story about getting to talk with Phil Smith!!

Here's an article from his site that's a good starter tutorial as well, many other papers there too:
http://ae6ty.com/Papers_files/QRParticle.pdf

Also, there's K9YC's presentation slides on how to do antenna matching using SimSmith...  a tutorial applied to a near and dear subject, but probably better after reviewing the basics:
http://audiosystemsgroup.com/PacificonSmithChart.pdf

And, another nice choice in the PC instrument catagory is this:
http://sdr-kits.net/VNWA3_Description.html  currently running about $450-600 depending on accessories.