Subject: Thermal and EM images of antenna ?
From: Wes Stewart
Date: 10/17/2004 12:05 PM Eastern Daylight Time
Message-id:

On Sun, 17 Oct 2004 14:27:31 +0200, "Thierry" - wrote:

|Hi,
|
|To illustrate technical articles about EM radiations, I' m searching for
|thermal images of antennas during transmission ?
|Images showing the EM field is welcome too (not radiation pattern but
|measured in situ and transposed in false colors)
|
|Any URL to suggest ?

Sure just buy a copy of this:

http://www.ansoft.com/products/hf/hfss/


Hmmm.. where are the thermal images of "antennas during transmission"? All I
see are simulation graphics, not antennas with power running through them.

73,
Chip N1IR

"You're wrong" wrote in message
...
To illustrate technical articles about EM radiations,
I'm searching for thermal images of antennas during
transmission ?

"Fractenna"
But a true thermal digital image of an antenna in situ
is very difficult, because of convection currents.

Huh? Run some high power into the antenna and click the shutter button.
What
could be simpler (assuming you have the right camera). Obviously need a
fair
amount of power.

Look good, but I haven't the detector. I know a lot of companies but I only
need images

Thierry


Could model it by simply looking at the current distribution in NEC
(current
equals heat, neglecting many other factors).

Comnection currents ?? rolls eyes Okay, run the experiment in a vacuum
chamber smirk.

A more common mode is to attach thermal sensors
[WITH LONGER DANGLING WIRES???] at
various points on the antenna and map the temp
as a function of time.

Bull feathers. The leads would *obviously* (duh!!) screw-up the operation
of
the antenna (unless you're proposing fibre optic temp sensors).



BTW - (giving you the opportunity to change the subject and not answer the
questions as per your normal MO thereby maintaining your extreme pompous
to
idiocy ratio), did we ever sort out who really invented or developed or
suggested or discovered radiocarbon dating???????

"Richard Clark" wrote in message
...
On Sun, 17 Oct 2004 11:57:02 -0300, "You're wrong"
wrote:

The world would be a better place if they sent most of the
researchers in this field on a one-way trip into outer space. The whole
field seems to be infested with idiots (perhaps too much time
experimenting
with cell phones?).

If I recall my reading of the "Hitchhiker's Guide to the Universe"
the telephone sanitizers were in the 2nd ship to leave - eh?

Adams' books are indeed full of crazy ideas. I liked all his series ;-))

Thierry


73's
Richard Clark, KB7QHC

"Fractenna" wrote in message
...
I believe you're about half-way to proving that Thermal Images are
impossible. What next? Santa Claus?


It has already been proven that Santa Claus is impossible. Too many
chimneys to
crawl down (let alone up: Claus is morbidy obses as I recall)) in one
night...


Perhaps the delta between our positions is that if the temperature
increases
are not significant, then I'm assuming that the information is not of
value

You miss the important issue. Heat is not dissipated at a point but over a
surface. If I take a soldering iron, for example, and distribute its 40
watts
of heat across a strip of 2 feet by 4 inches, for example, it won't get
very
warm in a differential way to ambient.

Hi,

Even if the difference is not important vs. ambient air, a good image
processing will improve it.
This is not the problem.
The first step if to find someone able to picture it...

Thierry, ON4SKY
http://www.astrosurf.com/lombry


That re-distribution of heat across a larger surface area is how heat
sinks
work.

Ergo, the increase in --temperature-- at a point of measurement--or even
across
an area or region-- can be small, even though the total amount of ohmic
loss
may be high.

Thermal cameras register differential thermal radiation losses, not
convective
losses (per se). And the heat is distributed across a surface, not a
point.

You can't take a picture of an antenna outside, and learn much about its
ohmic
loss, for example. (Too much convective cooling). Not unless its ohmic
loss is
confined to a small area, the air is rarefied and windless, and thus the
temperature differential is a few degrees or more and indicative of bona
fide
radiative thermal heating/loss.

Hope you learned something:-)!

Best,
Chip N1IR

"Fractenna" wrote in message
...
Bull feathers. The leads would *obviously* (duh!!) screw-up the operation
of
the antenna (unless you're proposing fibre optic temp sensors).

Actually, the real problem is that the RF can screw up the very sensitive
probe.


Hi,

We can also do record such images in a lab. In a cold chamber (10°C or
lower) and sending +1 kW tunes in the antenna
I am sure that with a sensitive thermal device like those sold by
http://www.x20.org/ we can do it.

Thierry, ON4SKY
http://www.astrosurf.com/lombry


The trick is to do on-offs of antenna power, and register the temperature
on
the offs. The duty cycle must be adjusted so that the equilibrium
temperature
is being sampled properly. Most of the time, the temp drops noticeably
after 30
seconds to a minute. In some cases, the probe can be quickly attached and
then
detached during the off cycle.

It's fun to do. Som experimenting shows how to mitigate 'to measure is to
disturb' issues.

Best,
Chip N1IR

"Richard Clark" wrote in message
...
On Sun, 17 Oct 2004 14:27:31 +0200, "Thierry" - wrote:

Images showing the EM field is welcome too (not radiation pattern but
measured in situ and transposed in false colors)

Hi Thierry,

Go to:
http://home.comcast.net/~kb7qhc/ante...elds/index.htm
and select any particular antenna style, observe the "false" color
mapping of near fields, and tell me if this is what you mean.


Hi Richard,

Fine... That gives already a good idea. Congratulaiton for the job !
If I can't find thermal versions I 'ld like to use those images. I will
contact you directly.
I bookmarked your link.

73
Thierry, ON4SKY
http://www.astrosurf.com/lombry



73's
Richard Clark, KB7QHC

"Wes Stewart" wrote in message
...
On Sun, 17 Oct 2004 14:27:31 +0200, "Thierry" - wrote:

|Hi,
|
|To illustrate technical articles about EM radiations, I' m searching for
|thermal images of antennas during transmission ?
|Images showing the EM field is welcome too (not radiation pattern but
|measured in situ and transposed in false colors)
|
|Any URL to suggest ?

Sure just buy a copy of this:

http://www.ansoft.com/products/hf/hfss/


Yes, I know. But I 'm short of money currently :-((
There also http://www.x20.org/
plus this one http://www.thermal-imaging-survey.co.uk/ maybe.

Thierry, ON4SKY
http://www.astrosurf.com/lombry

On Sun, 17 Oct 2004 20:36:27 +0200, "Thierry" - wrote:
Fine... That gives already a good idea. Congratulaiton for the job !
If I can't find thermal versions I 'ld like to use those images. I will
contact you directly.
I bookmarked your link.

Hi Thierry,

I got your email. Simply copy the pages to display where you want if
you wish. I am not particular about the vanity of copyright nor
"patent pending." You will note that I also provide both the antenna
designs and mathcad files for free too.

73's
Richard Clark, KB7QHC

Thierry wrote:

"Wes Stewart" wrote in message
...

On Sun, 17 Oct 2004 14:27:31 +0200, "Thierry" - wrote:

|Hi,
|
|To illustrate technical articles about EM radiations, I' m searching for
|thermal images of antennas during transmission ?
|Images showing the EM field is welcome too (not radiation pattern but
|measured in situ and transposed in false colors)
|
|Any URL to suggest ?

Sure just buy a copy of this:

http://www.ansoft.com/products/hf/hfss/



Yes, I know. But I 'm short of money currently :-((


Oy, seems anything will turn into a fight, these days! 8^)

Here is what I suggest as a low tech and perhaps a bit silly solution.

Get a number of aquarium temperature sensors. these are the liquid
crystal type that is put on the outside of the tank, with the
temperature indicated by color change. Place on the antenna with the
number of stickers chosen by your desired resolution.

Experiments should be run on a calm day, and ideally at the same
temperature (although you can calculate for the differences) each time.

Transmit, and check, record, and enter into a program that can map the
results for you, or map it out manually.

Binoculars may be needed to see the tape!

This is not as glamorous as a thermal imaging camera, which would have
it's own set of problems, but it should work, and be quite inexpensive,
requiring only more time on your part.

"Richard Clark" wrote in message
...
On Sun, 17 Oct 2004 20:36:27 +0200, "Thierry" - wrote:
Fine... That gives already a good idea. Congratulaiton for the job !
If I can't find thermal versions I 'ld like to use those images. I will
contact you directly.
I bookmarked your link.

Hi Thierry,

I got your email. Simply copy the pages to display where you want if
you wish. I am not particular about the vanity of copyright nor
"patent pending." You will note that I also provide both the antenna
designs and mathcad files for free too.


Thanks for sharing ;-)
73
Thierry, ON4SKY

73's
Richard Clark, KB7QHC