GPS internal / external antenna

[fly_boy]

Hi I am looking at getting a Lowrance GPS 3500c or 3600c for a Webster twinfisher runabout would the internal or external ariel be better?
Dont know much about gps's any thoughts would help!

[SatNav]

External antenna's should always be the preferred option. Internal antenna's do work but will never ever be as consistent as an external, never.

Just depends on how much of the unknown you are prepared to accept?

[-Henno-]

This is a topic I was about to bring up myself. I am considering the Garmin GPSMap 172C but according to the garmin site it comes in both external and built in antenna options.

Satnav: When you say internal antennas are not as consistent do you mean they will drop out more often because they are less sensitive and receive less signal?

[flyboy]

Thanks Satnav
does anyone else think the same

[seatime]

G'day fly_boy, if you have a canopy mount the aerial on top. the less interference the better.

[flyboy]

Thanks gelsec to mount on the top of the canopy the external aerial sounds the way to go.
Is there interference through the canopy?

[seatime]

Don't know how much interference a fabric and alloy bowed canopy will cause, but a direct line of sight is the preferred option with GPS aerials. If there is any way to reduce possible errors or dissolution of position, pursue that option.

rgds

[-Henno-]

My boat is an open tinny and I have my GPS 12 and sounder mounted on a ram mount in front of where I sit on the inside of the gunnel.

The other day I noticed my gps dropped out with nothing above it but clear blue sky and nothing around it except aluminium. When I took it out of the holder and put it on my leg and drove for a while it came good. The gps 12 has an internal antenna. I am wondering if that was just a bad patch of gps coverage or a reception anomole in my boat.

My question to Satnav and any other gurus is should the internal antenna on the 172C be less reliable if I am NOT putting it under a canopy?

Mark

[SatNav]

1. Internal antenna's are no more or less sensitive than an external

2. An Internal antenna has more chance of not receiving full signals due to being obstructed if mounted in a position so as to be obstructed

3. A fabric canopy has really no affect on GPS satellite signals

4. It's really nothing to do with the actual antenna but the position where the GPS is mounted. If a GPS with internal type antenna was mounted on the roof then signal reception would basically be no different to an external antenna, just a bit hard to read.

5. With internal v external there is a trade off 1) An internal is easy and simple to mount requiring no addit antenna wiring and in situations where there is no superstructure to mount an antenna then really no other option but there could be loss of performance "at times and for periods unknown" 2) An external mounted above any obstructions should always have the better view of the sky/satellites/signals but requires a suitable structure to be mounted on and additional antenna cabling to be run.

[SatNav]

1. Mooks, This GPS mounted inside the gunnel, is the antenna below the gunnel and/or hard up against the inside of the boat? If so then satellites being what they are and where they are could be obstructed by the side of the boat, especially aluminium. Just because there was nothing above it but blue sky does not mean there were any or enough satellites in view "at that time"

[flyboy]

Thankyou all for your help Flyboy