which is better, internal or external anntenna

davis · 07 June 2010, 16:07

Thinking of a new GPS, which is better internal or external anntenna, or is there any difference . The external is a bit dearer and you have the cable to route back to the Aframe, does anyone have an opinion, thanks

willk · 07 June 2010, 16:26

I have both, a Raymarine A65 (external ant. on A frame) and a Ray 435i, flush mounted (internal ant.) The GPS reception is MUCH poorer on the internal unit. However, when it was surface mounted, i.e. vertical in a bracket, the reception was a bit better. I suspected some interference between the antennae (dunno how or why) as when I moved the external unit from the console to the A frame, the 435i reception improved from useless to just poor.

davis · 07 June 2010, 16:35

My reason for thinking of an internal anntenna was less problems with cable to areial , also with it being on the console didnt think it would make much difference with a signal, also I was thinking that an external anntenna was more for a boat with a wheelhouse, so by what you have told me there is a difference

9D280 · 07 June 2010, 16:46

Just going to play devil's advocate here...... not the same units, so is it a fair test?

PeterM · 07 June 2010, 16:49

And to play devils advocate even more .....

I reckon the Garmin 276 on one boat I have with the built in aerial is better reception that the Navman with the Aerial on the A-frame on the other !

The Garmin improved a HUGE amount when I updated the software.....

If I had to replce the Navman I'd have a built in Aerial as less to go wrong/falloff/ short out etc .

willk · 08 June 2010, 11:35

You're all right of course but then, it wasn't a test, just my experience with those specific units. Both units are obsolete now so modern kit should be better. Points against external all accepted. I do like the clear view of the sky offered on the a-frame though. A couple of big lads and some other console clutter cut signals back quite a bit at certain times.

donegaldan · 09 June 2010, 09:01

The basics of propagation still apply with gps antenna,
Most antenna have a "best position" and typically this is achieved with a nice external antenna, most internal units get mounted at various angles from horizontal to vertical, with no consideration how the antenna is pointed. Also the size of the collector is generally smaller, so as not to interfere with cosmetics.

So thats what it eventually comes down to, cosmetics, external antenna pain in the A55 to install, but better performance, internal, quick and easy, will probably do the job, but in certain situations will not be as good.

Hope this helps !!

DonegalDan

Downhilldai · 09 June 2010, 12:41

I've just fitted a Garmin 551S to my little Searider. This unit has an internal antenna and is flush mounted in the console at an angle of around 30 deg from the vertical. I had doubts as to the effectiveness of the antenna, given it's position, but it really works well, with a stronger GPS signal than some of my external antenna Garmin units showed, even with the boats inside a building. I thought I may have had to lay out some extra dosh for an external antenna on the 551S, but this doesn't now seem to be the case.

Simon B · 09 June 2010, 13:51

Lowrance have had some serious problems with their GPS modules, unit since withdrawn and all their HDS units are now internal.

Automotive GPS (TomTom et al) have internal antennas. If this kit can work through glass quickly and has done reliably for years it should in marine applications. Or am I naively hoping for to much again!

donegaldan · 09 June 2010, 16:45

Simon,
Reckon you internal antenna is vertical in TOM TOM etc,
for viewing by the driver, this is why they get a clear view of the sky,
also the older garmin had a fold out antenna, that came out at 90deg to the viewscreen.

I'd imagine there should be best practice guides available with marine GPS ? to best angles to mount kit etc ?

Donegaldan

davis · 09 June 2010, 23:04

So if the unit was positioned on the console of the rib with a built in anntenna it should pick up a good signal considering there is nothing overhead to block it, and therefore it it would be as good as a unit with an external anntenna .

BruceB · 10 June 2010, 17:06

The only other thing to consider is the position of the aerial relating to the tranducer. I have both an internal and external aerial on my boat but run the whole system on the external. Apart from it is in a slightly better position for a clear view it is also directly above the transducer which means all my positions taken from wrecks are exact rather than offset by a few metres.
This may or may not be important to you unless you dive........