GPS - External Antenna or not?

It all depeneds on where you mount the unit. For myself I think they are mandatory as even on the top of your dash you have still wipes out half of the sky with the vehicle roof. Get the antenna on the snorkel or bull bar and you will have much better initialisation time and much more reliable tracking.

I have an external/internal antenna, you can mount it outside or use the suction cups to mount it to the top of your windscreen. I always planned to put it outside but I put it on the winscreen just to try it out (just above the mirror) and it has never moved an inch since and I get 12 sat's and 3m accuracy most of the time, so I don't think it's going to move! ;-)
It's a Garmin GPS II Plus.

We have an old (ancient ?) Garmin GPS II, and a samll magnetic low profile antenna which I pop up on the roof above SWHBOs head. It measures about 45mm square and is about 15mm high and is pretty unobtrusive , not subject to tree damage, and works like a champion. Wouldn't be without it. On the negative side it is actually an ACTIVE antenna, that is it contains a pre-amplifier which is powered up the small diameter coaxial antenna fron the BNC connector on the GPS. That means any standard batteries in the GPS itself get chewed up a lot faster. To overcome that problem I power the GPS from the 4WD battery. Using the little 4 pin plug at the back (these are now available in Australia for less than $10. In my case I use the direct-from-the battery UHF radio power lead which means the GPS is permanently powered up and I don't have to restart it every time I turn the engine on or off. It also preserves the GPSs own batteries for when I take it walking.

Bruce, mine sits on top of the dash and in open country I've never had a problem, only 3 sats needed for a lock. I have lost lock in the bush a few times. I'd say if you position it down lower then an external antenna is a must. If the gps doesn't have provision for an external antenna then use a re-radiating job such as sold by gpsoz.com

Truckster,

Why not get the one with the features you want. If it has external antenna then fine. If not or it doesn't work as well as you want you can then get a re-radiating antenna from GPS OZ or somewhere similar.

Truckster, I did read about re-broadcast antennas available for Meridians the other day. Apparently they provide better signal than in vehicle.

A friend with an older Magellan says that the sensitivity provides greater satellites than his even when seated well inside the car, something his would not and the reason he got his rebroadcast antenna for roof useage.

Be worth trying a few for a look at satellite receival strength and number.

My Garmin external ant. has a magnetic base. Sits on the roof just above windscreen & is safe from predators and tree branches. Gives best possible coverage from sats & has never dropped out in the forest, might though in deep shadyvalleys. Careful not to crimp lead feeding it inside.
Recommend setting up dedicated continuous 12v power supply otherwise it will revert to internal batteries when ignit is turned off. You can leave it turned on 24/7 it draws so little amps.
Easy to unplug and install mobile aerial & batteries if needs be.

I have a Garmin E-treck. Used it last weekend hooked to the computer running Oziexplorer. Worked well on the dash until we got into heavy timber and lost the sat until we came out the other side.
Looks like I have to go to the Explore Oz shop again
Vince

Truckster,
I've got a Garmin e-trex with an in car mounting kit - however this does not include an external antenna - as the e-trex range does not include this as an option.

I've mounted it so that it sits almost vertically facing the driver and haven't had a problem with it - it really depends on where you mount the sucker. As long as the unit has a good view of the sky you should be right.

I've compared reception with one of my mates who has an external antenna - and they both pretty much dropped out at the same time when travelling though a thick canopy of trees. Any GPS will drop out in these condtions.

However - when choosing a good value GPS for 4wding - I wouldn't go past the Magellan range - as they have large screens and are easy to upload maps to. I bought my garmin primarily for hiking -so it neede to be small and waterproof - and does what I need it to do in the car - no maps though and small screen.

- Dave

Truckster,

My Meridian Colour sits quite happily in the Cupholder just ahead of the gearshift in the Civic and locks onto satellites just fine. I got little or no improvement putting it up on the dash. I just put something in the bottom of the cupholder to lift it a bit so I can see the display and it works well.

I'll have to see how it goes in the Prado but it should be much the same. If it boundes around a bit I might secure it with some velcro or blu tack. Much better than spending $70 on the mounting bracket. I have the external power cord into the ciggy outlet so it just stays on when I am travelling.

One good part about having it below dash level is the reduced visibilty for smash and grab if I leave it hooked up while I am in a shop or servo.

If I go inside a building then signal strength drops rapidly but inside the car it seems fine, even down under the dash. I looked at the reradiating antenna but I don't think I need it.

StevenL

StevenL

Truckster, I'd leave off buying either the re-radiating or external antenna until you have your gps. My Meriplat (which you know well :-) ) works fine without an extenal antenna.
Just buy your unit with all the accessories you really need. If you decide to go down the Magellan line then get the vehicle mount, I like the one I've got which attaches to the windscreen. Get a genuine Magellan 12Volt power/data cable. I bought an aftermarket one and it doesn't attach to the vehicle mount properly unfortunately. The factory one allows the gps unit to slip in and out of the mount without having to undo the screw to the power/data cable. (very handy)
Get a couple of SD cards, having 2 allows you to play with different configurations on map sizes. (particularly if you use Discover Aus streets and tracks) There were some lagging issues particularly when using the larger 256Mb SD cards.
Get a card reader/writer at the same time. Even check what the rechargeable batteries and chargers (Check the charger voltage) cost over there. Some of the rechargeable batteries over there have a larger capacity than we can get here.
Also get the genuine Magellan case, it's well made with room to carry extra batteries.
Just get one Truckster, you know you want one. (it would be really handy on your Mt Stirling trip :-) )
Regards Andrew.

My Magellan Map 330 sits in its bracket on the dash(what there is of it) and regularly picks up 8 to 12 satellites without an antennna. Buy one, but I would say it is just somethijg else to break off out bush.

garmin III sits on dash-mount. used to lose signal in heavy bush/forest quite often.
external aerial on top of snorkel, never lost it since.
nb retraced some regular spots and found differences in waypoints from before aerial was fitted.
very rarely go below 9/12 sats now

It depends on the sensitivity of your receiver and the sky view on your dash. I would not buy one unless I need one. So just suck it and see