External vs Internal GPS antenna

[BigEd]

Buying a new chartplotter (most likely Garmin 292) not sure what to prefer for chart-table based plotter?
Not a big difference in price, but don't want to drill another hole for cabling and to have receiver fixed somethere in cocpit.

Up to now use notebook with Max-sea and USB antenna laid on chart table as well, did not have any problems aquiring sat signals.
So what is the real reason for external antenna?

 

[Aja]

I have the Garmin 182 with built in antenna mounted under the sprayhood. It doesn't lose signal. Easlily disconnected for safekeeping whist not on board and only requires 12 volts.

I am going to try and mount below at chart table this season for planning to see if it works there too.

Donald

 

[pvb]

If your USB antenna has worked OK, you'll probably be OK with an internal antenna version of a plotter. But an external antenna would give better reception in marginal conditions.

As well as the Garmin 292, have you also looked at the latest Lowrance plotters at the same sort of price? The 5200 has 480x480 pixels (3 times the definition of the Garmin) and the 5150 has 640x480 pixels (4 times the definition of the Garmin).

 

[BigEd]

Didn't consider Lowrance because of slow redrowing speed as per YM test. But my ald notebook which I use as a plotter redraws very slowly too. Not a big deal, just got used already to very fast new notebook.
Was going to order from Cactus and Garmin is among the cheapest only 20J more than 3,8'' Navman. Lowrance far more expencive.
I am on Cyprus and need to order from someone who sell on-line.

 

[Pye_End]

My Garmin (8 channel) with internal antenna works fine 99% of the time down below at my chart table.

Very occasionally loses signal - but very often (strangely) in the same places - round Deal/South Foreland; couple of spots the middle of the North Sea... Doesn't go out for more than a few minutes though.

 

[KREW2]

I have a Raymarine handheld, works fine mounted under the spray hood on boat batteries. I can disconnect it take it down to the chart table with no signal loss where it works off its own internal batteries, or the cigar lighter socket for more prolonged periods.

 

[pvb]

Cactus prices...

Cactus is indeed cheap for Garmin, but can be uncompetitive for other makes. As an example, the Navman 5380 you mentioned is £370 at Cactus but only £339 inc UK delivery at JG Technologies. Similarly, the Lowrance 3600 is £449 at Cactus but only £359 at JG Technologies. The Lowrance 5150 is £339 at JG Technologies. From experience, I'd say JG's mail order service is good. It's always worth a quick Google before you order!

 

[boatmike]

The only reason for external antenna is if you don't get a good signal below ( I don't) If you are only using it for planning on your computer and what you had before was OK IMHO don't bother.

 

[Guest]

Redraw speed .....

That's already been shown on a previous thread to be suspect ... as the result doesn't agree with many users of Lowrance gear. I have Lowrance and never notice slow redraw at all ... in fact I reckon it's pretty quick !

You will also have the opprtunity to have a chart card good enough for most at far less cost than competitors ... often bundled with the plotter.

As to original question ... I have a plotter with external antena ... just after I bought - the internal version came available ... as previously I used to have my eTrex GPS hang inside cabin and worked fine and my Lowrance antena was lodged in cabin window behind curtain ... I would have preferred the internal version.
But there is the question of marginal coverage - then the external is better ... but do you normally sail in a forest or in amongst tall buildings ?

/forums/images/graemlins/wink.gif

 

[Anonymous]

Boat building materials (including wood and GRP) absorb some of the GPS satellite signal. Clouds and rain also absorb signal. Furthermore, water in and on decks absorbs yet more signal. So you could find that everything is fine until the sky clouds over and it starts to rain - when the signal becomes marginal or fails.

On my Nauticat 42, my Navman on internal antenna is marginal below decks - most of the time I run it below on the integral antenna as it gives me more data than the NMEA feed that I get from my Raymarine head which is actually the master GPS for the boat even though I tend to use the Navman as the primary plotter. I have two brackets for my Navman, one below (marginal on internal) and one aloft which is fine in all weathers. I strongly advise you to arrange an alternative outside position for yours if you are going to rely on an integral antenna.