MonsterFM.com / Broadcast Technical Services

 

 

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50 Ohm Co-Phasing Harness

Connect Two (or more) Antenna Bays Without a Power Divider

A "phasing harness" allows 2 or more antenna bays to be co-phased or bound together as if they were one single  antenna exhibiting higher gain.  By phasing 2 antenna bays together you can increase your antenna gain by an average of 3dB which is the same as doubling your effective radiated power.

In order to phase the two (or more) antenna bays, they have to be fed in phase. Additionally, as you are combining two 50 ohm antenna bays into a single 50 ohm feed, we have to deal with the resulting impedance mis-match.

The phasing issue is resolved by feeding the antenna bays with two (equal length) feed-lines that are an odd number of quarter waves in length. 

The impedance issue is resolved by making these lines of 75 ohm coaxial cable.

The calculated total length of the phase line is cut in half, then assembled using standard connectors and a "T" connector with the 50 ohm feedline (from the transmitter) connecting to the bottom (input) of the "T" connector.

Ideally, to enjoy maximum benefit from stacked antenna bays, the antenna bays should be 1 wavelength length apart (this yields maximum gain and narrowest pattern).

 

Phasing Harness Calculator    -    By MonsterFM.com / Broadcast Technical Services

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