|
|
|
|
Dipoles - RF Cafe Forums
|
|
| S4C
|
|
Post subject: Dipoles
Posted: Fri Jan 14, 2005 11:24 am
|
|
|
|
A basic question concerning Dipole elements. I apologize
for my ignorance, and any help would be greatly
appreciated. As I understand it: A dipole
element is cut to 1/2 wave length of a desired frequency.
Question: Why? Background: Im studying
Chaff and why it works as a Radar Jammer. I know
that chaff is made of many strips of dipole elements
cut to 1/2 of the wavelength of the target "victims"
radar frequency. This allows the reflected RF to
present itself on the "victims" radar scope.
Why 1/2? Why not the full wavelength? What would
would happen if it was cut to the full wavelength
instead of 1/2? I think the reason is that the dipole
element would not reflect if cut to the full wavelength...but
I dont know why. Any help...? God
Bless, -S4C
|
|
| |
|
 |
|
Guest |
|
Post subject: 1/2 wave vs Full wave Reflector.
Posted: Sat Jan 15, 2005 8:05 am
|
|
|
|
|
I would suggest that you download the EZNEC demo
and give it a try.
|
|
| |
|
|
|
|
S4C |
|
Post subject:
Posted: Tue Jan 18, 2005 11:14 am
|
|
|
|
Looked at the program mentioned.... hmmm....I
am not an expert in this field...far from it. I
looked at the EZNEC and im not sure what I could
learn from it. Pretty obvious by the question I
originally asked, I am not an expert. I
am currently studying Chaff, and needed a little
more information on how it works. Specifically,
why the dipole elements are cut to 1/2 the wavelength
of the victims RADAR frequency...and not to the
full wavelength. I stumbled across this
website while searching for information. I figured
what a great place to ask the question...a forum
used by "professionals" in the RF field of study.
Again, I respectfully ask for any "laymans"
help on the question asked. God Bless,
-S4C
|
|
| |
|
|
|
|
Kirt Blattenberger
|
|
Post subject: Dipole chaff
Posted: Tue Jan 18, 2005 4:16 pm
|
|
| |
| Site Admin |
 |
Joined: Sun Aug 03, 2003
2:02 pm Posts: 308 Location: Erie, PA
|
A 1/2-wavelength dipole resonates at a specific
frequency, depending on its physical dimensions
(primarily length if the aspect ratio is high).
Therefore, it is very efficient at reflecting an
incident signal at the resonant frequency of the
dipole. Integer 1/2-wavelengths probably
work as well, but waste storage space and add weight.
I recall reading somewhere that less than a pound
of well-designed and deployed aluminum chaff can
reflect a signal equivalent to a large bomber (same
radar cross-section, or RCS). There has got
to be lots of information for you to reference on
the web. I suggest trying a Google Search.
- Kirt Blattenberger
|
|
| |
|
|
|
|
Guest |
|
Post subject:
Posted: Tue Jan 18, 2005 5:49 pm
|
|
|
|
Thank you for your reply Sir! When you say
"integer 1/2 wavelengths", does this mean the same
as "full wavelength" (as opposed to 1/2) ?
I have done many Google searches...in fact that
is how I found this fine website and forum
I understand your reply to say: When
dealing with Chaff, a dipole cut to the full wavelength
of a victims RADAR freq will have the same effect
as a dipole cut to 1/2 the wavelength. 1/2 wavelengths
are then used to save space and/or weight.
Thank you for your time and your patience...
-S4C
|
|
| |
|
|
|
|
Kirt Blattenberger
|
|
Post subject: Integer multiples
Posted: Tue Jan 18, 2005 11:49 pm
|
|
| |
| Site Admin |
|
|
Joined: Sun Aug 03, 2003
2:02 pm Posts: 308 Location: Erie, PA
|
Your interpretation of my comments is correct.
Integer multiples of 1/2 wavelength are as follows:
1 * 1/2-wavelength = 1/2 wavelength 2 * 1/2-wavelength
= 2/2 = 1 wavelength 3 * 1/2-wavelength = 3/2
= 1-1/2 wavelengths 4 * 1/2-wavelength = 4/2
= 2 wavelengths ...and so on.
- Kirt Blattenberger
|
|
| |
|
|
|
|
Guest |
|
Post subject:
Posted: Wed Jan 19, 2005 3:28 pm
|
|
|
|
Thanks again for your reply. It is very helpful!
-S4C |
|
Posted 11/12/2012
|
|
|
|