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Shark Fin DIY

MINI has an amazingly complex antenna system called the diversity antenna. It includes a signal amplifier; logic board to select from two antenna arrays; and pounds of wiring. What Shark Fin as Intended to Be Usedmakes it amazing is that it sucks. It’s another example of unnecessary complexity that keeps creeping into automotive design. In this post we aren’t ready to pitch it entirely but we will eliminate the aerial and the base (saving 4 oz at the highest point in the car and eliminating a major source of drag).  We’ll make the CravenSpeed Shark Fin Antenna designed for the 2002-2004 antenna base work with a 2006 (larger) base.

[If you’re wondering about installing the Shark Fin on a 2002-2004 R53 MINI: It’s super easy — zero wrenches on the difficulty scale. Basically steps 1 & 2 below, attach the wire to the base, and attach the Shark Fin to the car. 3-5 minutes tops.]

Difficulty:3 wrenches
Difficulty Scale
Proceed only if you’re comfortable with Soldering and using a cutting wheel. (Interesting that so many of my projects involve cutting wheels….)
Tools & Materials Required:

  • Phillips Screwdriver
  • 22mm Socket & driver
  • Soldering Iron
  • Optional: Silicon sealant, grommet, and expanding foam

Time Required: 45-60 Minutes
I found a quote about the antenna system online attributed to a book called “MINI Complete” that states:

The Aerial Diversity Unit has coaxial inputs from the roof aerial and the rear screen aerial amplifier unit. The unit also has the output coaxial to the radio headset and a radio on wire. The switching action of the diversity unit is configured to ensure that no noise is heard through the radio (diversity crackle). The unit constantly scans the aerial inputs for the best signal, which is then fed to the radio headset via the coaxial cable. The diversity function is only operational in the FM mode, when AM stations are being received the diversity function is deactivated.

Let’s see if we can keep the functionality, but fit it into a sleeker form factor. Since the CravenSpeed Shark Fin was designed for the earlier (smaller) base, we’ll just eliminate the base entirely.
Remember there is no warranty if using the shark fin in this way and a new base will set you back $50-$150 if you aren’t satisfied. Make sure you get a good seal or you will get water leaks. We’re using three strategies to leak-proof: Adhesive tape; a grommet; and expanding foam.  Water will always find a path if it’s available so there’s no guaranty what we are describing will work for you. Proceed at your own risk.

Instructions

  1. Remove the aerial from the stock base.
  2. Attach the wire to the antenna mount and test fit the Shark Fin over the base.  Even if it doesn’t fit over the base, turn on your radio and make sure it works before proceeding.
  3. If it fits, congratulations you have the older style (smaller) mount and you’re halfway done. Use tape to mark out where you want it to be; put adhesive on the bottom of the base without removing the tab; attach wire to antenna mount; test fit again; if all is good-to-go, then expose rest of the adhesive and press firmly in place.  You’re done.
  4. If it didn’t fit over your base in step 2, then keep reading.
  5. In the photos below, I removed the extra tab on the bottom, but it isn’t necessary if you’re removing the stock mount completely. Turn the Shark Fin over and attach the adhesive keeping the red 3M side down.
  6. Before you remove the stock mount, put down some tape and mark the center-line of the vehicle.  This will make it easier to line up later.
  7. Work your way to the underside of the base. Gently separate the roof liner from the roof until you can get your hand on the base nut. Use a 22mm socket to work it loose.
  8. Follow the wires back to a junction panel and unplug them.  The smaller wire simply unplugs.  The coaxial wire has an unnecessarily complex plug, so go ahead and break the pink pins and save time.  You’ll tape it back together later.
  9. Pull the antenna base free of the car. (Now is a good time to clean the roof that was under the old base with a clay-bar.) The bottom of the base is attached with four impossibly small Torx screws. Unscrew them if you have the appropriate sized Torx bit. Since this base is getting junked, we just drilled them out.
  10. Separate the halves and you will see a small logic board and enough room for a small Sat-radio antenna.  That must have been the reason for the redesign — to make room for a second antenna. [If you have an aftermarket sat radio tuner like XMDirect, you could probably squeeze a small Terk antenna into the Shark Fin before you seal it up.]
  11. Use a Dremel cutting wheel and free the logic board. Since cutting is easier than splicing coaxial cable, you’ll save time this way.
  12. Solder a small piece of wire there to have a lead to make the connection to the Shark Fin where the old antenna base made contact with the board.
  13. Cover the backside of the logic board in electrical tape.
  14. Drop the wire through the hole in the roof and test-fit the Shark Fin.  Use the tape with the center-line as a reference. Step back and look down the roof to make sure it is straight.  Tape all around the Shark Fin, then remove it again.
  15. Place a grommet in the hole in the roof and seal it with silicone sealant.
  16. Drop the wire from the Shark Fin through the opening in the roof and connect it to your logic board using the nut and screw provided with the Shark Fin.
  17. Reconnect the plugs (using tape to secure the one you broke) and plug them back into the junction panel.
  18. Tuck the logic board between the headliner and the roof, circuit side down so you don’t make contact with the roof.
  19. Position the Shark Fin roughly where you want it but do not attach it just yet.  Turn on radio and check that everything works as expected.
  20. If radio works fine, proceed to the next step.  If not, retrace your steps and troubleshoot.
  21. Fill the underside of the Shark Fin about 50% full with low expanding foam sealant. Wait for it to expand until it is almost level with the bottom.
  22. Remove the red film to expose the adhesive and position it where you marked it earlier. Hold it in place with tape and weigh it down until the foam dries.
  23. Check under the roof to see that a little foam is expanding through the opening in the roof.
  24. Reattach roof liner and ensure hatch seal keeps it in place.
  25. When foam has dried, remove tape.
  26. Put a band of silicon sealant (black or white) around the base to prevent water leaks if you want an additional level of protection.
  27. Stand back an admire your handy-work.

Antenna PartsSharkFin UndersideUnder baseIMG_3226Use Tape to Mark Locationseal grommetInsideBaseFreed BoardUse foamPress down FirmlyCheck Under-sideInstalled Shark Fin