FOLDED UNIPOLE
 

The folded unipole is basically the same  as a detuning skirt.  The main difference is that the detuning skirt acts to tune out the signal from an AM broadcast station, while the folded unipole becomes the antenna for the AM broadcast station.  AM Broadcasting explained how the AM tower is actually the antenna, with the tower sitting on a base insulator to place it above ground.  When a tower operates above ground, special techniques must be used to go across the base insulator.  This includes lighting circuits and any other antennas. 

There are two methods to place additional antennas on the AM tower.  One is with the use of isocouplers, with one isocoupler required for each transmission line that goes across the insulator, regardless of whether it is transmit or receive.  The second method is with the use of the folded unipole.  The folded unipole is attached to the tower is the same manner as it would be for a detuning skirt.  The tower is then grounded, and the AM broadcasting transmitter, after going through a matching network, is attached directly to the skirt.  This procedure is not a new one.  It has been done for many years.  It is best to do this on a non-directional broadcast tower, however, it can be done on a directional array. 

The advantage of adding a folded unipole to a tower is that the tower can then be used to rent space to cellular and pcs carriers for various types of antennas.  It is also an advantage for lightning protection to have the tower grounded. 

AM Coordination Service customs builds the folded unipole / detuning skirts for many types of towers.  Contact us for the technical details on how to add antennas to an AM broadcast tower.