Subscribe To This Site
XML RSS
Add to Google
Add to My Yahoo!
Add to My MSN
Subscribe with Bloglines

Home
AC Current
AC Motors
AC Generators
Amplification
Antenna Principles
Basic Electronics
Batteries
Blog it!
Capacitance
Circuit Control
Circuit Measuring
Circuit-Protection
Cable Connectors
Conductors
DC Current
DC Motors
Diodes
Electron Tubes
Games
Generators
Gyros
Hoplinks
Inductance
Logic
Meters
Microwaves
More-Antennas
Oscillators
Our Visitor's
Power
Power Supplies
Project Videos
RADAR
RADAR-Parts
Radio Waves
Reactance
Resistance
RF-Antennas
RLC-Circuits
Safety
Servos
Soldering
Special Logic
Specialty Tubes
Survey
Synchros
The-Oscilloscope
Spectrum Analyzer
Tubes Cont. -
Transformers
Transistors
Transmission Lines
Trans. Lines Cont.-
Tuned Circuits
Voltage
Waveguides
Wave Propagation
Wiring Techniques
 

Folded-dipole

The use of parasitic elements and various stacking arrangements causes a reduction in the radiation resistance of a center-fed, half-wave antenna. Under these conditions obtaining a proper impedance match between the radiator and the transmission line is often difficult. A convenient method of overcoming these difficulties is to use a FOLDED DIPOLE in place of the center-fed radiator. (See views A and B of the figure below).

Folded-dipole antennas







A FOLDED DIPOLE is an ordinary half-wave antenna that has one or more additional conductors connected across its ends. Additional conductors are mounted parallel to the dipole elements at a distance equal to a very small fraction of a wavelength. Spacing of several inches is common.

The feed-point impedance can be further increased by using three or four properly spaced parallel conductors. Standard feed-line SPREADERS are used to maintain this spacing when required. In any folded dipole, the increase of impedance is the square of the number of conductors used in the radiator. Thus, a three-wire dipole has nine times (32) the feed-point impedance of a simple center-fed dipole. A second method of stepping up the impedance of a folded dipole is to use two conductors with different radii, as shown in view B.

The directional characteristics of a folded dipole are the same as those of a simple dipole. However, the reactance of a folded dipole varies much more slowly as the frequency is varied from resonance. Because of this the folded dipole can be used over a much wider frequency range than is possible with a simple dipole.

(back) (top) (return to antenna principles page)







Subscribe to this site!


Enter your E-mail Address
Enter your First Name (optional)
Then

Don't worry -- your e-mail address is totally secure.
I promise to use it only to send you Learn-about-electronics.


SiteSearch Google

Can't find what you are looking for? Enter your search here.

Custom Search



Translate your page

If English is not your first language you can Translate the text on this page to any one of the languages found in the drop down menu. Select your language from the list for an instant translation.



Find it on Amazon

Looking for something unique? Try our Amazon search engine.




Our Visitors


Find out what our visitors think. Add your own words and get featured. Just click on the link.

Lacy from Florida Writes... This site is amazing, it's great to see a site where it is all right there in plain English, clear and understandable. Thank you for your help

Lisa, from anytown USA, writes... OMG! Your site helped me with my science report on Covalent Bonding, thank you so much. Rocking Site man.




Online Reference
Dictionary, Encyclopedia & more
Word:
Look in: Dictionary & thesaurus
Medical Dictionary
Legal Dictionary
Financial Dictionary
Acronyms
Idioms
Encyclopedia
Wikipedia
Periodicals
Literature
Other languages:
by:



Around the World!

Click on the Clustrmaps map to see where this site has been helping people learn about electronics in the last 24 hours.

Locations of visitors to this page

You are the

joomla analytics
unique visitor to this site.