Roof Antenna

Both of these can decrease reception to some degree. If you don't experience bad reception without it, then it's probably not worth it.

Krieger

Steve, are you having reception problems? Do you have tinted glass? Do you prefer not having the unit on the dash or on or near the glass, and putting it down on the console limits reception? Have you tried a beanbag mount on the dash where the antenna can see the birds?

You don't get any greater reception if that's what you're asking.

The answer is a good, solid, it depends.

Running my 660 in my Mini Cooper, an external antenna wouldn't make much of a difference, the flap antenna has a good view of the sky.

But when I put it in the Jeep (Grand Cherokee), an external roof-mounted antenna helps a lot, as its usual mounting spot leaves the antenna really occluded.

Check to see how many birds your 660 can "see" and go from there.

I have one and my accuracy went from 13 - 16 feet to 8 - 11 avg.

There's already a recent thread on this topic. http://www.poi-factory.com/node/17418

So not really worth the money spent, your talking 5 feet difference. you could have used the 20 bucks or less for something better.

Bob

This may sound lame, but when you say "how many birds your 660 can see" are you referring to bars of recption, or am I missing something here?

Birds = Satellites

It absolutely makes a difference. Especially when I'm in Manhattan. Call it extreme or whatever you want, but I get a very weak signal without the external antenna connected. No tinted windows or any other obstructions in the vehicle.(Toyota 4Runner & 660) The lack of signal or bouncing signal make the gps pretty much useless. Until I plug in the ext. ant. and my signal strength is back. I can't believe that the external mounted ant. can in any way, hurt your reception.
Now, if most of your driving is OUT of the big city, then it won't do much more, but it certainly won't hurt. I think they should be included with every gps that accepts a antenna.
If you want one, Ebay is a good place to look.
(and no, I don't sell them)

In todays economy, that's my .8 of a cent:)

Just like it sounds -- how many can your 660 see?

Bring up the status display -- you'll see concentric rings with numbers representing the satellites. The numbers that are blinking, or are dark are the satellites you should be able to "see" from your position, but aren't getting a signal. There's also the list along the right side of the screen -- the ones without signal strength bars are those birds you should be able to "see" but can't.

In the Jeep, the metal roof blocks out a large chunk of the sky, largely due to where I have the thing located, which is near the radio, and the antenna is pretty well obscured.

In the Mini, because of where the Nuvi is sitting (and probably the construction of the car) less of the sky is blocked by overhead metal.

learning something new every day! Thanks