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Author Topic:   GPS Reception Under Bimini Cloth
blackdog54 posted 01-26-2007 09:10 AM ET (US)   Profile for blackdog54   Send Email to blackdog54  
I have a 1985 Montauk. I [may buy a] Garmin 492 GPS, sold either with internal or external antenna. As I never have more coverage than a cloth bimini, is there any reason to think the internal antenna is NOT the right choice? I would mount the unit on the center console.

Does the external antenna offer any better satellite coverage. Buying today, any feeback appreciated.

I know several other Montauk owners have gone with the mushroom external antenna, just wondering why.

Thanks! Linda

bluewaterpirate posted 01-26-2007 09:23 AM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
You'll have no problems with the installing 492 with an internal antenna under a bimini. It will have no effect on reception.


jimh posted 01-26-2007 09:42 AM ET (US)     Profile for jimh  Send Email to jimh     
A woven fabric cloth such a typically used in boat canvas is transparent to the radio waves at the frequencies used in GPS reception.
davej14 posted 01-26-2007 12:07 PM ET (US)     Profile for davej14  Send Email to davej14     
My experience is with a Lowrance unit which has a pretty poor internal antenna. Although the Bimini had no measurable effect on reception, the mounting position of the unit with the internal antenna had a significant effect. I ended up returning the unit for one with an external antenna which had far better reception. I am convinced that the Garmin units have better internal antennas, but I would encourage you to experiment with position before drilling the mounting holes. Of course if you opt for the external antenna you will have stronger reception and more flexibility for mounting.
Royboy posted 01-26-2007 11:11 PM ET (US)     Profile for Royboy  Send Email to Royboy     
I used a Garmin GPSMAP76CS, which is a handheld unit, under a bimini quite a bit and had no problems with the signal.


JOHN W MAYO posted 01-27-2007 06:56 PM ET (US)     Profile for JOHN W MAYO  Send Email to JOHN W MAYO     
I have not checked the prices lately, but the external was not that much more expensive if you at a latter date wanted to use the unit on another boat which might block the signal some. If you buy the external antenna seperately, it is Alot more expensive than buying a unit initially with the external.
where2 posted 01-27-2007 10:35 PM ET (US)     Profile for where2  Send Email to where2     
I can use a Garmin or a Standard Horizon with internal antenna under a Bimini, it's a non-issue. I prefer having one less thing to disconnect when I take the GPS off the boat for secure storage.

jimh posted 01-28-2007 09:37 AM ET (US)     Profile for jimh  Send Email to jimh     
Another advantage of a GPS receiver which has a self-contained antenna is the device can function when away from the boat installation. This makes it useful in other settings, such as on the dashboard of your car.
blackdog54 posted 01-28-2007 12:58 PM ET (US)     Profile for blackdog54  Send Email to blackdog54     
Well, I got the Garmin 498 GPS, with an additional transducer, it also provides depth, fish, H2O temp. I had a Hummingbird FF that did the same, however, the top of the console would be VERY crowded due to prior owner's layout.

So now I have 2 issues:

1) Getting the transducer cable from the transom, through the in-deck tunnel up to the CC. I am certain that the fit is tight, given everything else in there. I bought an electrician's fish wire (snake) to try and get it through.

2) My Hummingbird and E-trex were grey/black format. Am I going to have difficulty in direct sunlight with the color format? I rarely use the bimini and am worried that I will not appreciate the color in bright light. Has anyone else mounted this on their Montauk, and if so, was this an issue? Before I undertake this transducer task, I want to be sure that I have the right GPS for my application.

I pulled the bait tank out to get at the bilge entrance to this through-deck fitting. Now I want to pull the batteries off as well and really scrub the area down since I have access. What finish product do you recommend for the non-skid area as a sealant? I want something that will minimize stains and dirt from setting in BUT not defeat the purpose of the non-skid.

Thanks, in advance-


ConB posted 01-28-2007 01:41 PM ET (US)     Profile for ConB  Send Email to ConB     
Linda, if you are removing an old transducer cable, tie a strong light line to the end of the old cable to pull the line though the tunnel. Then tie the new cable to the line to pull it though.


blackdog54 posted 01-28-2007 09:46 PM ET (US)     Profile for blackdog54  Send Email to blackdog54     
Well, that electrician's fish snake/wire was the way to go. I pulled the cooler away from the front of the center console, fished it to the stern via the in-deck tube, taped it to the transducer and pulled her aft. 2 minutes effort, an hour's planning. $12 tool made it effortless.

Tested the Garmin in modest sunlight in my driveway, so, not bright sunlight and no glare from the water but the visibility, resolution, image-all quite good.

I have decided not to re-install the bait tank. I really don't fish. It is a Kodiak Pro-flow 22 gal. oblong, with a 700 GPH bait tank pump. The tank and pump out the door at West Marine are about $330. Will sell to forum member for $200-almost NO USE. I am in San Diego, if anyone is interested.

Thanks for the input of all who responded. Would still like a recommendation for a product for the non-skid.


David1877 posted 02-06-2007 05:40 PM ET (US)     Profile for David1877  Send Email to David1877     
I have a hand-held GPS which I use in the car and on the boat with a suntop. It seems to work ok regardless of the direction of travel.

I think you will be ok with the internal antennae.

pglein posted 02-12-2007 02:38 PM ET (US)     Profile for pglein  Send Email to pglein     
The modern color displays seem to actually be easier to see in direct sunlight than the black and white units. A lot of R&D money has been dumped into making the more desirable color units even more desirable, while the less desirable black and white units probably haven't changed in ten years.
davej14 posted 02-12-2007 05:51 PM ET (US)     Profile for davej14  Send Email to davej14     
Your color display probably also has several brightness level settings. If it doesn't look bright enough make sure you are set to high brightness. In the evening this will be too bright so you will need to change it to a lower brightness setting.
bluewaterpirate posted 02-12-2007 09:37 PM ET (US)     Profile for bluewaterpirate  Send Email to bluewaterpirate     
Go to page 65 of the Garmin 492 Users Manual. It will tell how to set your Garmin up to automatically control the backlight in reference to sunrise/sunset. It's real simple to do.


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