Dual CB Radio Verticals

Using CB Vertical antenna’s co-phased for forward directional extra gain.

 

Co-Phasing can be used if you have Two vertical antennas and some room.

PRO’s

  • Forward Directional Gain
  • Low Cost
  • Can be different types
  • Simple Construction
  • Low SWR
  • Vertical Polarisation

CON’s

  • Fixed Direction
  • Mounting and Spacing
  • Vertical Polarisation

 

The solution to obtaining good forward gain from 2 verticals is to feed the 2 antenna array “90 degrees OUT of PHASE”

This concept transforms the normal 360 degree verticaly polarised radiation from one vertical antenna and takes the bi-directional concentrated radiation of adding another close by,  forcing both antennas into a forward projecting beamwidth.

This “Out of Phase” configuration forces the two antenna’s normal bidirectional operation into each acting differently, similar to a two element verticaly polarised beam.

One Vertical Element acting as a Director and the other acting as a Reflector depending on the Phasing Harness connection.

This is despite the fact that both are “Driven” vertical elements as both are connected as normal to the coax phasing harness ends.

The actual direction is determined by the length of the co-phase harness side connected to each antenna.

To create the “90 deg.out of Phase” condition the coax “T” splitter has two different lengths of  75 Ohm TV High Quality coax terminated in a PL259.

One coax length is a Quarter Wave (at center operating frequency)

and the other coax side is a Half Wave long terminated in a PL259.

So the Phasing Harness needs to be constructed from a SO239 Splitter with one side a 9′ length of  SEVENTY FIVE (75) OHM (TV High Quality) Coax to a PL259 to plug into the leading or Director antenna.

The other side needs to be a 18′ length of 75 Ohm TV Coax to a PL259 to plug into the following or Reflector antenna.

This will create a directional vertically polarised array with reasonable gain if positioned 1/2 Wave length apart.

Its not a technical evaluation,  but I have proved the dual 90 degree Out of Phase antenna configuration does provide about 1-2 S Points over the one vertical antenna alone in the chosen direction.

I have also tried this with a 9′ Stainless Vertical and a DDRR. (Direct Driven Ring Radiator HERE)

The DDRR has the inherent advantages of small size and earthed radiator giving low static floor as well as slight vertical directivity.

Dual-antennas

This original content by AX05 is Copyright CQDX11.net 2012