I haven't used a Smith Chart in over 30 years, and to say the least, I'm a
bit rusty. I'm thinking there must be computer programs that can do the
calculations with values you just plugs in. Any recommendations? I'm
specifically interested in finding the impedances of antenna whips much
shorter than 1/4 wave.
--
Bob D.
ND9B

I'm curious. How do you use a Smith chart to find an antenna impedance?

There certainly are programs specifically designed to find such things
as antenna impedances. The free EZNEC demo program from http://eznec.com
would be adequate and ideal for your purpose.

Roy Lewallen, W7EL

Bob D. wrote:
I haven't used a Smith Chart in over 30 years, and to say the least, I'm a
bit rusty. I'm thinking there must be computer programs that can do the
calculations with values you just plugs in. Any recommendations? I'm
specifically interested in finding the impedances of antenna whips much
shorter than 1/4 wave.

On Sun, 9 Jul 2006 17:30:57 -0500, "Bob D." wrote:

I haven't used a Smith Chart in over 30 years, and to say the least, I'm a
bit rusty. I'm thinking there must be computer programs that can do the
calculations with values you just plugs in. Any recommendations? I'm
specifically interested in finding the impedances of antenna whips much
shorter than 1/4 wave.

There's a nice impedance spiral in Kraus: "Antennas".

I haven't used a Smith Chart in over 30 years, and to say the least, I'm a
bit rusty. I'm thinking there must be computer programs that can do the
calculations with values you just plugs in. Any recommendations?

For Linux (and probably other Unix-type systems running X) there's a
nice free program called Linsmith.

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

Smith Chart 3.0 is great.
http://www.antennadesignassociates.com/smithexample.gif

On 2006-07-09, Bob D. wrote:
I haven't used a Smith Chart in over 30 years, and to say the least, I'm a
bit rusty. I'm thinking there must be computer programs that can do the
calculations with values you just plugs in. Any recommendations? I'm
specifically interested in finding the impedances of antenna whips much
shorter than 1/4 wave.

For real operating systems (anything Unix based -- Linux OSX or a real Unix)
try Linsmith http://jcoppens.com/soft/linsmith/index.en.php

You will find half dozen programs which deal with performance of short
verticals at the website below.

From the Index, go to "Download programs from here" and read the
one-line description under each program name.
----
.................................................. ..........
Regards from Reg, G4FGQ
For Free Radio Design Software go to
http://www.btinternet.com/~g4fgq.regp
.................................................. ..........

Bob D. wrote:
I haven't used a Smith Chart in over 30 years, and to say the least, I'm a
bit rusty. I'm thinking there must be computer programs that can do the
calculations with values you just plugs in. Any recommendations? I'm
specifically interested in finding the impedances of antenna whips much
shorter than 1/4 wave.

Hi, Bob -

http://zaffora.f2o.org/W9DMK/W9dmk.html has one.

About 3/4 of the way down the page.

It won't help you find antenna impedance unless you plan to measure the Z at
the input end of the line and use the tool to get antenna Z. As has been
said, you can use EZNEC to model your antenna and get its impedance.

However, a Smith chart can be very useful for matching a thing to another thing.

The one I use (a demo) I got from the University of Applied Sciences in
Berne, Switzerland. I like it. However, it appears that it has been removed
from the host. If you want it, I can send it to you. It is zipped to 306 kb
in size.

Cheers,
John

Andy adds:

I have often used a modified Smith Chart , called an
Impedance/Admittance
chart , to do matching..... If the impedances are not greatly
mismatched,
it is very easy and accurate.... and very very intuitive...

The ones I used have the impedance cordinates in black and the
admittance coordinates in red.....

I found them extremly useful in the design of an automated antenna
tuner
which I designed for a Texas Instruments Marine SSB unit, back in the
late 70s..... You could literally track the impedance transormation
mentally
with series and shunt elements.....


Andy W4OAH

"AndyS" wrote in message
ups.com...
Andy adds:

I have often used a modified Smith Chart , called an
Impedance/Admittance
chart , to do matching..... If the impedances are not greatly
mismatched,
it is very easy and accurate.... and very very intuitive...

The ones I used have the impedance cordinates in black and the
admittance coordinates in red.....

I found them extremly useful in the design of an automated
antenna
tuner
which I designed for a Texas Instruments Marine SSB unit, back in
the
late 70s..... You could literally track the impedance transormation
mentally
with series and shunt elements.....

Andy W4OAH
==========================================
As an Engineer in my eighties with a long association with
transmission lines of all sorts I have never used a Smith Chart, in
anger, in the whole of my life. I have always used log tables,
sliderules, pocket calculators or, more recently, dedicated computer
programs.

Use of mathematics gives one a more 'intuitive' insight into how
transmission lines work than any chart. But it's a just a matter of
opinion and depends on one's basic education.

As useful as they were only at HF, Smith Charts became redundent when
the personal computer came in. Old habits die hard!
----
Reg.