Freenet Antennas

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There is an alternative mod for these antennas; the Mpot mod. Both 'The Mpot Mod', and this ('The RC Mod') work well. Their primary difference is in mechanical strength of the completed antenna mod. I feel my mod (RC Mod) is more sound mechanically.

Click on any of the photos here to see full scale.

Step 1 - Disassemble the Antenna and Feed Horn

1. Undo the nuts holding the feedhorn onto the grid and the mounting bracket.
2. Carefully remove feedhorn. Note: It is easy to break the 'wings' of the grey metal bracket on the end of the feedhorn.
3. Remove the screw on the end-cap of the feedhorn, remove the bent aluminium sub-reflector.
4. Keep the screw and sub-reflector.
5. Place the feedhorn on a bench, place a sharp knife blade in along the join where the end-cap of the feedhorn is glued on, and tap the blade with a hammer...moving around the feedhorn as you go.
6. Undo and keep the nut on the F-connector. Remove and keep the washer.
7. Place F-connector on a hard surface and push down on the feedhorn. The F-connector should slowly disappear inside the feedhorn as the chassis starts to emerge from the housing.
8. Pull chassis out of housing.

Step 2 - Cut off Dipole

Using a sharp knife, heavily score a line where the printed circuit board extends from the chassis. The picture below shows the Dipole after reassembly - but you get the idea.

Step 3 - Remove Circuit Boards from chassis

Simply use a chisel and hammer to remove the chassis boards. Throw them away.

Also - use an allen key (or pliers) to remove the small bolts that were holding the chassis in place.

Step 4 - Remove contents of F-connector

The threaded connector at the end of the chassis is called an F-connector. You must remove the center of that connector, so the CFD200 coax can pass though. Do not try and drill it out - it will not work.

The barrel of the F-connector (right side of the picture) is comprised of two threaded sections.

1. Using pliers, unscrew the barrel from the chassis. It will come apart at either of the two locations marked with a red line in the above picture.
2. Unscrew from the other red-line location. Your barrel should now be it two pieces.
3. Push out the contents of the barrels.
4. Reassemble the barrel.
5. Screw barrel back onto the chassis.
6. Drill an extra hole about 1/8" dia at the dipole end of the chassis. In the picture above, it is the circular hole towards the left end. This hole is for a cable tie...that we will attach later.

Step 4 - Modify (Re-tune) Dipole

When used for MMDS TV, the dipole is tuned for 2.2 GHz. To retune to 2.4GHz, we reduce the key dimensions by 10% as shown in this attached photo.

1. Shorten the dipole (the horizontal wings in the pictures) by 10%.
2. Shorten the length of the balun (the vertical bit in the pictures) by 10%. Both sides.
3. Use a file or sandpaper to remove all the excess circuit board track material. Both sides.
4. Use a file to create groove below the dipole. It should be wide enough that the coax cable fits neatly.
5. Solder a new shorting bar as shown in the picture. You can use a short length of copper center conductor from coax. It should be soldered as close possible to the bottom of the two-legged part of the balun.

Step 5 - Attach Coax cable

1. Pass the bare end of the CFD200 cable though these parts in this order:
   • Rubber boot (see last picture below for correct orientation).
   • F-connector washer
   • The base of the feedhorn
   • The hollowed-out F-connector
2. Remove approx 10mm of the black jacket from the CFD200 coax. Do not remove the wire braid.
3. Fan the wire braid out in a uniform circle. Take a clump that represents about 20% of the total , and twist together to form a thin 'wire'. Solder together. Cut off the other 80% of the braid.
4. Remove the thin foil, exposing the white insulator.
5. Trim the coax exposing approx. 2mm of the white insulation followed by 2mm of the copper center conductor.
6. Solder copper conductor to the dipole/balun as shown here:
   
   
7. Solder the braid to the shorting bar as shown here:
   
   
8. Position the Balun/Dipole against the end of the chassis, and secure the cable with a cable tie.
   
   

Step 6 - Re-assemble and Waterproof

1. At this stage, everything should now look like the picture here - except the housing covers everything.
   
   
2. Apply liberal amounts of silicon sealer around the F-connector, and the cast bracket at the end of the feedhorn.
3. Tighten the F-connector nut onto the F-connector.
4. Add a dob of silicon to the holes/posts at the dipole.
5. Run a bead a silicon around the sealing surfaces for the end-cap.
6. Place end-cap in place. Clamp for 24 hrs.
7. Re-attach the aluminium sub-reflector.

Click picture to show full size.

You can buy a kit of parts from our Online Store.