GPS Antenna Location

T

toyman

New member
Fan-C-Dory has a Garmin 4210 installed, with the antenna mounted on the roof.

I have a Garmin 498 That I am going to mount over toward the passenger side. Yesterday I was putt-zing around with the 498 - checking to make sure it still worked p inside of my metal building. It worked just fine. Then I started thinking, my Sirius antenna is inside the cabin (laying on the shelf) and it works just fine. The Nuvi seems to work wherever I put it in the car. Is there any REAL reason for the GPS antenna to be outside, especially in a fiberglass boat ?
 
If it works, nope. We have the GPS puck laying on the top shelf and it works well.

Thinking about that, I think I'll move the external GPS antenna from the radar arch to just under the radar, inside the boat and see how that works. One less thing to lay down when covering the boat. Also doesn't get irradiated when we use the radar.

Good idea.

Boris
 
I have used three different Garmin GPS units, (60C, 192C and 478) all with built in antennas, and they have worked very well. I sometimes carry an inflatable on the roof, and I have my VHF mounted above the GPS unit (s) with the extra radio antenna wire laying on the self above the forward windows. Never a lost signal.

Robbi
 
The latest chip sets in Garmin (and most other GPS units) will work inside of even buildings and cars without even a clear view of the sky. So yes these will all work well, since the fiberglass is transparent to the frequency of the GPS signal.
 
Dave

I've never felt the need for external antenna and never lost gps reception in the boat with Lowrance 100, Garmin E map and Garmin 276C. And don't plan one for the Garmin 545. The Lourance 100 and 276C provide the antenna and signal to the computer for the Nobletec Software. On land have lost signal many times in deep forested canyons or some not so deep, but very thick like the California redwoods.

With Bob's post I now know why. I hope this means with my new Garmin Colorado 400C that it won't lose signal even in the dense woods.

Jay
 
I would think that the fewer possible obstructions the better and I would mount it outside and high up. We do lose Sirius signal and even GPS in Alaska on a regular basis. Why compromise when a potentially better mounting is available?
 
If you mount the puck on the visor you won't have to deal with the possibility of water entering the core material in the roof.
 
My new GPS unit that i will be installing also has a internal antenna, they are great..all you need to buy is a adapter for your trucks power point and it works great in the truck also. Tug
 
Before we all rush to trade in our external antennas for an internal version, please remember that in antennas, size matters. So while antennas internal to the GPS may work great 99% of the time, the larger size of an antenna external to the GPS does add margin for low level signals.

The point asked above was if moving the antenna inside would work. And the correct answer is: fibreglass and resin are transparent to RF frequency and putting an external antenna inside would be OK, if not shielded by metal equipment. The larger size of an antenna external to the GPS unit gives a stronger signal, which is always good.

Boris
 
In Alaska, one is often limited by the sky view; where the satellite signal is obscured by mountains. Our experience in SE Alaska was that GPS worked well in all areas, except where the sky was blocked. There were areas (such as Ford's Terror) where even Ham radio signals were blocked. In most areas our Sirius antenna on the electronics shelf inside the boat worked fine, but a view of the Southern sky was necessary because of the satellite location.

The latest chip sets use very small and very efficient antennas. Many "internal" and "external" GPS antennas are very similar in size. The attenuation by various materials can be a consideration, but in our experience, the signal strength was very similar with internal and external antennas. The newest chip sets are much more sensitive.
 
My Garmin GPS antenna works ok mounted under the roof, inside the cabin, and so does the Microsoft USB GPS antenna on my laptop, but my handheld Geko 101 that I have as a battery-operated back won't work unless I go out in the open air.
 
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