ETS-Lindgren 3147 Log Periodic Dipole Array Antenna - Manual (Page 16)

To attach the included adapters to the Model 3147:
1. If required, insert the 1/4–20 thread insert into the polarizing adapter.
2. Remove the mounting knob from the mounting bracket on the antenna.
3. Slide the polarizing adapter into the mounting bracket by placing the
polarizing adapter placed between the shoulders of the mounting
bracket.
16 | Mounting Instructions