[Windows Mobile Development and Hacking General] Nakebod:
I hope this topic is in the right section, it's a little bit hacking, isn't it? (Otherwise feel free to move.)

Before today I experienced a poor FM radio quality with the original Touch Diamond headset, so I couldn't properly use TMC, via HyperGPS.

At my home I had a few spots with TMC reception, but sometimes moving a few inches/centimeter could result in a total loss of the TMC signal.

Driving around with iGo and TMC was even more terrible, on a 50 KM (~31 miles) trip I had 3 succesfull TMC receptions, for a few seconds that is.

With other words, HyperGPS worked perfectly, but my own reception quality was very very poor.

So after some research on the extUSB pinout, I've decided to build my own antenna.

Getting an extUSB connector

I few weeks ago I've bought a few USB to 3.5mm headphone adapters, so I could "waste" 1 if it didn't work out that well.

These connectors are highly useable for this small project.

I managed to open the connector with a screwdrawer, don't force it or the clips will break.

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As you probably can see, there are 3 wires connected in the original connector.

On pin 6 a green wire for the left speaker.

On pin 7 and 8 a yellow/gold-ish wire for the antenna and the ground (?) wire for the left and right speaker

On pin 11 a red wire for the right speaker.

With a soldering iron I was able to heat the wires a little bit, so they came loose.

When you are done, pull of the big flexible plastic part, and save it for later. (Dunno the name of it)

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Wire

Now, find some wire. I've read that 1.5 mm thick cable is perfect.

I didn't have 1.5 mm, so I used a 1.0 mm thick cable. And now I'm done, I'm glad I didn't had 1.5 mm as it would be more difficult to attach to the connector.

About the cable length, some say 75 cm is perfect. At this site they say 95 cm is the ideal lenght for a 5/8ths lenght antenna. (Whatever that means tho, I'm not that technical. Something to do with the wavelength.)

My cable is currently 110 cm, and I haven't seen any negative effects yet. Maybe I can have an even better reception with a shorter cable, but at this point I don't see a reason why I should risk my current quality.

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Connecting the wire

We need to solder the wire to both pin 7 and 8.

But the pinout image shows only pin 7? Indeed, but with only pin 7 connected the phone doesn't recognize a headset, thus the FM Radio isn't working. (And probably also HyperGPS, didn't test this.)

The headset detection can be skipped via a registery edit, but I think this solution is more solid, since the reg edit has to be done each time you reset your phone, or connect a real headset.

Be sure your wire doesn't hit other pins, in the worst case it could seriously damage your device.

Finishing the connector

To add a little bit more strength to the cable, I've added a little bit glue.

Re-attach the flexible plastic part we kept separate earlier.

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Done

When you connect the antenna, the phone will now recognize a headset, so you can listen to the radio without attaching your headphones, and without performing a registry edit to fake the headphones.

But the best of all: I have a much better TMC reception.

I haven't tested it in a real world trip, but so far the reception indoors is perfect, without loosing the TMC signal every second.