ARI Sanremo Home Page Home Page Nominativo di Sezione ARI Sanremo
Home Main Menu Sezione ARI-RE Award Liguria EME Diploma Sanremo Search Members Downloads Forums Guestbook Login

Toggle Content Trova nel sito

Toggle Content .:Translate Language
Please select to change language

Klicken Sie auf Sprache ändern

Sélectionner pour changer la langue

Haga clic para cambiar el idioma
Autori › Coaxial Balun
Coaxial Balun

Coaxial Balun

This Balun, (adapter from Balanced Line to Unbalanced Line and vice versa), use one section of ¼ wavelength and one of ¾ wavelength in coaxial cable.
This device requires that the electrical length of both sections include the ¼ wavelength coaxial transformer.
The unbalanced impedance value has exactly the same value of the coaxial cable. For this reasons the name is just 1:1 balun but the purpose of this device is to match any impedance value.
The length difference between the ¼ wavelength and the ¾ wavelength sections provides the necessary 180° degrees electrical phase-shift, as required, for ex. from the open dipole radiator.
Since the narrow bandwidth, this balun is well suited for the monobander antenna only, therefore is particularly indicated to couple the radiator of the VHF/UHF Yagi-Uda antenna, but is possible to use successfully in the HF also.
Remember to take account of the electrical length of the coaxial cable, the speed factor (ex. 0,659 for the RG58, but it depends on the own cable speed factor). So please, use your own particular cable specifications.
Instead of the 1:1 Balun, is possible to couple the 50 or 75 Ohm unbalanced Line or with any unbalanced line to any balanced Impedance value. To do it, is enough to replace the two ¼ wavelength pair's transformer with two sections, always of coaxial line, at calculated value. This is better understood from the figure given like immediate explanation as the 1:1 Balun example.

As shown in the balun image, the 1:1 balun is done by the

[ ¼ W L * V c ] coax cable section of Z c impedance;
and the
[ ¾ W L * V c ] coax cable section of Z c impedance;
which is refolded three times in order to obtain the same physical length of the shortest section, this is not the electrical requirement, then it is for practical layout convenience only.

WL is the Wave Length; WL = ( constant light speed / frequency )
Vc is the Velocity constant or propagation speed factor in the coax cable; i.e. the electrical length.

The mathematical simplified formulae for the calculation is simply:

Z c = s q r t ( Z o * Z i ) { Z c is the Impedance value in the coaxial cable }
Z o = ( Z c * Z c ) / Z i { Z o is the resistive impedance at antenna balanced value }
Z i = ( Z c * Z c ) / Z o { Z i is the final unbalanced value seen at the Rx/Tx coaxial line }

Practical Example of 1:1 Balun, ready to use on 144 MHz made by RG58 (for use in QRP only):


Italian version

(74097 reads) Printer Friendly Page

[ Return to I0QM ]

Nominativo di Sezione
Sezione A.R.I. Sanremo - 18.02 codice ASC che per la Sezione è G08

La Sede si trova in corso Mazzini n° 1, a fianco del Campo Sportivo, in Sanremo. La Sezione è aperta tutti i martedì, non festivi, dalle ore 21 alle ore 23 circa.

Indirizzo Postale:


Scrivi al Segretario
Indirizzo di posta elettronica certificata

Webmaster IZ1OQB PINO

Contatto per il Webmaster
Regolamento del Sito | Note Legali/Disclaimer | Come trovarci

Best viewed 1024x768 +

Questo sito appartiene alla Sezione ARI di Sanremo (IM) e non rappresenta una testata giornalistica in quanto viene aggiornato senza alcuna periodicità.
Non può pertanto considerarsi prodotto editoriale ai sensi della legge n. 62 del 07.03.2001.
I loghi, i marchi e gli script usati in questo sito appartengono ai rispettivi proprietari e a CPG-Nuke Team.
Questo sito utilizza la versione 9.2.1 di Dragonfly CPG-Nuke.
Theme by i1yst
Tutti i testi, le foto e i disegni tecnici sono esclusiva proprietà di © 2002-2013
Vietata la riproduzione e la copia, anche parziale, senza la previa autorizzazione di

All content are protected by the copyright law and may not be copied without the express permission and the active reference to a source!
Web stats

Interactive software released under GNU GPL, Code Credits, Privacy Policy

placeholder Support   Dragonfly   XHTML valid!   CSS valid!   Level Double-A Conformance icon, W3C-WAI Web Content Accessibility Guidelines 1.0   RSS valid!   Robots valid!   PHP   PhpMyAdmin   MySql   Get Adobe Reader   Unicode   Add to Google placeholder