external vs internal antenna

[motocross269]

I am looking at buying a new gps/sonar combo for my boat.  What are the benefits of a external antenna over a internal.  I see most guys are running external antennas, but I have traveled all over the world with a handheld using internal antennas and have had no real problems unless I am in an enclosed vehicle or building.
Does the shared external Lowrance antenna act as a hub for Networking between two units???

Thanks,

[Slipkey]

Motocross,

The gap between the two is pretty small now, but there are two key factors that still make most people choose the external antenna for fixed mounted GPS over the internal:

- Satellite aquisition - number and strength -  this has to do with the way the antenna is positioned: with a fixed mounted GPS with an internal antenna, position for best viewing and best signal are rarely the same.  On average you are going to have better strength and number of satellites with an externally mounted antenna because it's positioned where it can be most effective.

- Median error - ties in with the number of satellites aquired but you tend to have a higher median error with internal antennas than with external because of the above factors.

The network connection to share an external GPS antenna between two units isn't the hub per se.  Is part of the chain of signals that are passed through the network.  Here's a sample diagram of a network to give you an example of what I mean:  http://www.lowrance.com/Products/Marine/LowranceNET/LowranceNet_sample.asp.

Hope that helps.

[motocross269]

So then if I understand you correctly the External Antenna would go into Waas mode quicker because it is better at acquiring satellites.

Thanks alot...This has been really helpful. I will probably be making a purchase within the next week or so.

[smbassman]

The external antenna can be linked to two (or more) GPS units in NMEA 2000 units.  The internal antenna signal can only be used by the one unit.

For a good signal, the internal units must be mounted upright with a clear path to the sky.  These are not recommended for bow applications where the unit is laying nearly flat.  This is especially true on BassCat's where the unit is down in the well for the recessed TM pedal.  They also are not recommended for In-Dash mounting.  I have an internal antenna unit at the console, but it is mounted on the rail, upright and with a clear view of the sky and it seems to work very well.

[stackenem]

I actually have one of each on my boat and really don't see any difference in them. They both seem to come up quickly and don't lose their signals very easy. I have a Lowrance 332c in the bow and a Eagle intellamaps 502c on a ram mount at the helm.

[SethV]

I have a pair of 332's on my boat linked with the network.  I went with the external for 2 reasons, as stated above.

I wanted to use a single GPS antenna, and share waypoints.  You can share with the internal antenna, but you can't share a single antenna.

I also have my front unit flush mounted, can't do that with the internal antenna.

The network is so cool.  I love being able to punch in a waypoint and see it on both units, and when fishing off shore it is great not having to look back at the console anymore.  I will never have a boat without 2 GPS units.
Only thing I would do different is get a bigger screen at the console.  The 332 screen is way too tiny for me to easily see when the water gets rough.  I don't have smartcraft on my Merc, so I added the fuel flow sensor to the network.  It is great knowing exactly how much fuel I have used and how quickly I am using it.

Seth

[Langer]

Seth, why dont you go and buy a bigger screen, and I will take the 332c off your hands for you. 

[SethV]

Brian-

How about I sell both 332's to you for $19,500 and I throw the boat in for free!!!   

I am selling the boat after the Regional this year, so I will just wait for the new boat to make sure I have the big screen.

Seth

[Langer]

Hmmmm.... Tempting......