understanding building and using baluns and ununs download

EgĬommon Mode – No Balun Let Zcc be 0 ohms which is in series with Zcm. Now E1 = E2 – balanced voltage across load due to balanced load – not balun.

Egīalanced Load – Balun Let Zcc be Hi-Z due to ferrite beads on cable and R1 = R2. WØINK February 2009īalanced Load – No Balun Let Zcc be 0 ohms which shunts R1.

Typical construction is ferrite beads over coaxial cable or wires on ferrite core.

Can be use for unbalanced to balanced loads like dipole antennas and beams.

Primary use is for reduction of common mode currents.

Current baluns are typically 1:1 - Zout = Zin but can have other ratios.

An example is the TV antenna 300 ohm to 75 ohm matching transformer. => Provides for impedance matching of transmission line to antenna.

RF in the shack or transmitter location that can cause RF current to flow through the operator! WØINK February 2009.

RFI to nearby devices like TV sets and telephones.

Pattern Distortion – caused by radiation from transmission line due to common mode current on transmission line.

Generation of CM Current From an Antenna idĬommon Mode Current is generated on the transmission line because of imbalance of displacement currents (id) around center of dipole antenna.

Why are common mode currents undesirable?.

How are common mode currents generated?.

BALUN is name of device that can be many things like a common mode choke, unbalance to balance transformer, and a step up or down transformer.

Name suggest device converts between “Balance Unbalance”.

Balun formed from BALance – UNbalance.

Loss of power to antenna due to mismatch between coax and antenna.

The above are due to “common mode currents” on the transmission line.

The BALUN & Antenna Problems What is a BALUN? The Current BALUN The Voltage BALUN Why & How to use a BALUN? Selecting a BALUN VIRGIL LEENERTS WØINK ARRL Technical Specialist Email –

Understanding building and using baluns and ununs download