Dipole Building 101

You've received a box of MWA antenna equipment! Here's how to put one together.

Equipment you will need:

• PH1 screwdriver
• PH2 screwdriver
• SMA wrench
• Mallet
• Plastidip
• Sharpie

1.Lay out the materials.

Remove a hub, its attached cables and four (4) aluminium wings from the box.

2. Remove the plastic lid from the top of the hub and set the screws aside. 

North (N), south (S), east (E) and west (W) are marked on the LNA underneath the four corner pins. These four pins are where the LNA attaches to the wings. The LNA board juts out between the north and east pins. This part sits in a notch so that the LNA can fit inside the hub.

3. Lift out the LNA.

Carefully lift the LNA free from the hub by feeding more cable into the bottom of the tube. 

4. Check the coaxial cables.

Look at the underside of the LNA. Check that the white cable is connected to the Y-pol connector, and the black cable to the X-pol connector. The labels are written on the LNA. 

5. Tighten the cables.

Use an SMA wrench on both connectors, which will ‘click’ when they have been sufficiently tightened.

6. Attach the wings/legs.

With the LNA removed, attach the wings to the hub, ‘feet’ first. Each wing should slot fairly easily into the groove. Use a small hammer to tap the wing all the way into place if necessary.

7. Replace the LNA.

Place the LNA back into the hub, so that it sits atop the wings. Fix in position with the four short screws.

When the hubs were assembled, a horizontal dash ‘-’ should have been marked on the outside of the hub, representing the north-west face of the dipole. This is determined by the LNA. The LNA can only sit properly in the hub in one position, because of the part that juts out.

8. Mark the north-west side of the hub.

Check to see if the dash is marked on the outside of the hub between the north and west pins. If it is, draw a vertical dash across it, so it becomes a plus ‘+’ sign. If the dash has been marked anywhere else, draw a ‘+’ sign in the correct position.

9. Apply Plastidip.

This coating protects the LNA from the environment (the MRO soil is quite acidic). In a well-ventilated area, apply two coats of plasti-dip to the top of the LNA, waiting a few minutes between coats. 

10. Secure lid of hub.

Replace the hub’s lid and secure in place with the two thinner, longer screws.

11. Adjust wing/leg length if necessary.

The legs of the dipoles are not set to a standard height when given to us, so there is usually some variation. To fix this, extend all of the dipole legs to maximum, by loosening the screw on the leg and pulling it, and then tighten the screw again. This step can be done before attaching the wings to the dipoles if preferred.

12. Install the dipole in a place of your choosing!

Use the north-west marker (the plus sign) on the outside of the hub to orientate the dipoles correctly when placing them on the mesh. Then you just need to lay the cable and connect it to a beamformer!