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Thread: The Diversity Antenna System: Two Antennas

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2014-01-16 17:28:40
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The Diversity Antenna System: Two Antennas
The "diversity" antenna system used two separate antennas with the stock Nissan head unit, one vertical antenna in the front fender (in most cases) and one horizontal antenna embedded in the rear window glass above the defogger grid. The stock Nissan head unit could switch between these two antennas for best reception, benefiting most in urban areas where signals bounce off buildings, causing what is known as multipath interference.

How can you tell if your car has two antennas? Sitting in driver's seat look over your right shoulder. Is there a single wire connection at the top passenger side of your rear window? Yes? Then you have an antenna in the rear window as part of the diversity system. Many people dismiss this as part of the defogger, but if you look closely at the glass you'll see they're not connected. This means at one time you also had (and may still have) a diversity antenna plug behind the head unit. It can be identified by two center prongs side by side. One prong leads to the mast (vertical) antenna, this is the thick cable off the back of the diversity plug. The other prong leads to the antenna (horizontal) embedded in the rear glass, this is the thin wire off the back of the diversity plug.

So if I still have the diversity plug do I need an adapter to convert it to a single prong "non diversity" plug for an aftermarket head unit? Nope. Follow the thick cable back from the diversity plug a few inches and you'll find a hard piece of plastic wrapped in foam. Plugged into the back of this is a standard "non diversity" single prong plug! Pull it out, plug it into the back of your aftermarket head unit and just stuff the diversity plug back in the dash.

But don't I need both antennas? No. The stock Nissan head unit had diversity switching in it and unless your aftermarket unit has this feature (AND a double prong jack on the back) two antennas really aren't going to make any difference. Even the stock head unit worked with only one antenna, albeit without the diversity switching.

Can I use an adapter to go from the diversity plug to a standard plug, unhook/remove the vertical antenna and only use the rear glass antenna? I've never tried this, but in theory yes. Most FM radio stations broadcast in both vertical and horizontal polarization so the horizontal antenna in the rear glass should work to some degree if you have everything connected properly. One note is that the rear antenna does not have a ground wire with it like the vertical (front) antenna, so no ground to the head unit chassis with this antenna. This shouldn't be a problem if your head unit is mounted/grounded properly with the factory brackets.

Last edited by SE-RMonkey on 2014-01-16 at 20-38-33.
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