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Old 03-26-2015, 11:07 AM
2real4u 2real4u is offline
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Location: Chicago
Join Date: Oct 2012
Posts: 8
Mein Auto: E60
DIY - E60 NBT retrofit diversity antenna

As some of you may know, there is a difference between MASK/CHAMP/CCC/CIC antenna configuration and NBT antenna configuration. MASK, CHAMP, CCC and CIC use antenna diversity. There is a powered (using RAD_ON signal from headunit) antenna amp on the right side of the rear window. The antenna amp switches between antennas using a rectangular voltage spike signal from the headunit. In this setup the headunit receives the signal from just one antenna at any given time, but can switch between them on demand.

With NBT the setup is different. NBT receives signals from two separate antennas simultaneously and uses digital signal processing to filter out noise and amplify the radio signal using the phase difference of the antenna signals.
Refer to the picture below. On the left side is the MASK/CHAMP/CCC/CIC setup. On the right side is NBT setup.

Since NBT is not capable of sending the 'switch antenna' signal to antenna amp, retrofitted NBT in a car with legacy antenna amp setup will only use the default, FM1 antenna for all radio reception (if the retrofit adapter provides RAD_ON signal, or if power for antenna amp is taken elsewhere - NBT does not have analog RAD_ON).

This means that unless the antenna amp is modified, NBT will have the worse reception of radio including traffic info than the headunit that is being replaced.

Luckily there is a fix for this. One needs to retrofit the correct diversity antenna amp system into the car.

I will be showing the example for US market E60. For other markets refer to WDS and Rheingold schematics.

First of all, let's have a look at E60 antenna amp. It is located under the headliner on the right side of rear window. It uses spring contacts to connect to the leads of the antennas in the rear window. It is used for both radio and remote lock/unlock. We have to keep it at least partially functional for remote lock/unlock to work, but we will need to modify the radio part.

I'll be using F30 diversity antenna amp for this DIY. The reason for choosing F30 amp is its' small size and independance from remote central lock antennas.

You would need the version for NBT-equipped F30. It does not have RAD_ON signal (at least in US version) and has diverisy antenna output (two or more FAKRAs, depending on the market).

The part number for the US antenna amp is 65209231178

Now comes the fun part. We need to modify E60 amp to pass the radio signals from antennas to F30 amp.

First we need to figure out the antenna lead relation to actual antennas in the rear window.

For E60 it is below:

For F30 the setup is less complicated:

As you may have noticed, the FM2 and FM3 antenna locations on E60 closely resemple the position of FM1 and FM2 antennas on F30 and cover the majority of the surface of the rear window, providing maximum antenna coverage, but maintaining phase difference.

We need to connect disconnect the signals from AM, FM2 and FM3 antennas on E60 from stock amp and route them into F30 amp.

If we start counting from E60 fakra connector, AM is the second spring contact. FM2 and FM3 are first and fifth from FAKRA.

On F30 amp side we an use the following pinout. Disregard RAD_ON, it's not present. For US we need to connect FM1, FM2 and AM to leads 2, 4 and 5 on 6-pin connector. If your F30 amp came without a connectorm you'll need part 61136909058 for connector housing and three standard BMW bushing contact leads.

You'll need to open the E60 amp, disconnect the SMDs that connect to spring contacts (I've soldered them vertically so that the change is reversible, but it is not necessary). For FM there are 2 SMDs that need to be disconnected. For AM there is just one.
Now solder the leads going to F30 amp in place of SMDs (to pads that connect to spring contacts) and route the wires through the recesses in the PCB separating the amp sections. Make sure the leads are facing the front of the car with the amp installed, otherwise they will be visible from the rear window.

Put everything back together. Use 3m tape to tape F30 amp somewhere above headliner.

Connect the black radio FAKRA to black connector on NBT and F30 amp. Run another FAKRA wire from F30 amp to NBT and connect it to the second connector on both sides (white on NBT, pale green-ish on F30 amp).

Enjoy perfect radio reception with retrofitted NBT. Your radio traffic reception will also improve, as well as IBOC signal strength in US. You'll also note that there will be no antenna-related errors in NBT.

PS. Since we did not touch the remaining two FM antennas on E60 antenna amp, it is still functional for FM, so if you are installing NBT retrofit in multiple steps, you can use the modified E60 antenna with your old MASK/CHAMP/CCC/CIC and it will still work for FM.

Last edited by 2real4u; 03-26-2015 at 02:51 PM.
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