External GPS antenna install, avoiding interference?-gctid349721

[Guest]

My Garmin GPS/Chartplotter arrived yesterday, and I'm gearing up for install.

The external antenna included says to route the antenna wire away from any electrical wires, but I'm stuck here. The only way to run the antenna wire from the dash that will conceal it is to run it behind the guages, behind the shifter, and up the rear corner of the alaskan bulkhead to the hardtop.

The majority of the boats wiring harness is obviously here behind the guages and where the shifter is.

Could I wrap the antenna in a shielding of some type and run it along with the boats electrical harness until it breaks out into the open to eliminate any interference?

[Guest]

Almost all of the electrical equipment I have purchased has a note to that effect. Suggest you try it the way you want, test it see if it works, if so make it permanent. Sound like you a going to rout it much the same way I did mine.

[Guest]

I guess I can pop one of the guages out and run it thru the hole before I drill another hole in the dash, just to test it.

Just wondering if anyone has had any luck with shielding the wire and what product they used?

[Guest]

It will likely work as planed. Don't assume the worse. Try it! (With EVERYTHING running, including the motor!)

If it is really a disaster ...

Buy some cable TV cable.

Look at it before you buy it!!

You want the type with the braided shield.

The other type has aluminum foil wrapped around it. :thumb

Use a razor blade to lightly scratch the plastic cover of the wire from one end to the other.

Do NOT cut all the way through to the braid.

Now, start at one end and peel the plastic cover off like a banana.

The scratch makes a weak line and it will peel off as fast as you can pull.

Attach the center of the TV cable to the GPS Cable. ( Might have to remove the connector if it a large one!)

Use the center of the TV Cable to "Fish" the GPS Cable through the braid.

You now have a gps cable with a braided shield.

Ground the shield as needed!

[Guest]

Just keep it away from the radar if you have one, fried my gps ant. by mounting it too close to the radome.op-

[2850Bounty]

I think that a portion of the advice/warning is a disclaimer to a certain degree. The antena cable will be shielded.

As the others have said, try it!

[dktool]

I used the under deck mount and put it near the bow, works great.

[img]/media/kunena/attachments/vb/652686=24535-WIND9.jpg[/img]

[Guest]

rkcarguy wrote:
My Garmin GPS/Chartplotter arrived yesterday, and I'm gearing up for install ...up the rear corner of the alaskan bulkhead to the hardtop.

Good thought DKTOOL!

It is a GPS antenna, It needs a clear view of the sky, Not a clear view of the horizon!

There is no advantage to a high mounting.

The satellites are 10,000 miles UP, moving the antenna up, 12 feet closer will make no difference.

As long as there is No/Minimal metal above the antenna, you could mount it under the floor and it would be fine.

Fiberglass and Wood are nearly transparent to the GPS signal.

The Antenna is inside of a Fiberglass/Plastic case to begin with.

Mount it under the console if you want!

Take a handheld GPS and hold it in your planned location.

If the handheld works, the Better, Garmin Marine Antenna will be just fine.

I/we will say it again. Just Try It! :coo-

[2850Bounty]

If we own an external GPS antena that is intended to be mounted somewhere on the exterior of the boat, why would we NOT take advantage of this?







18" extension



4 foot extension



Or no extension

[SomeSailor]

UncleWillie wrote:
Good thought DKTOOL!

It is a GPS antenna, It needs a clear view of the sky, Not a clear view of the horizon!

There is no advantage to a high mounting.

That's incorrect. GPS satellites orbit the earth every 12 hours or so. The sooner you can pick them up as they rise in ascension and the longer you can hold them in descension, the more accurate your positional fix will be.

You want your GPS antenna to be as high as possible, preferably above and out of the line of sight of your radar and with an unobstructed view of the horizon.

[2850Bounty]

I'm not well educated on this, but I'd have to say that I agree with Mike. That would seem to make good sense.

[SomeSailor]

The idea is you wanna catch the satellite as it's coming up the horizon (your system knows where it's coming from btw... through the almanac log) and once you get that fix (earlier the better) your system gets a 3D fix. Once directly overhead... it's virtually worthless.

[2850Bounty]

SomeSailor wrote:
The idea is you wanna catch the satellite as it's coming up the horizon (your system knows where it's coming from btw... through the almanac log) and once you get that fix (earlier the better) your system gets a 3D fix. Once directly overhead... it's virtually worthless.

Well, while I still see logic to the antena being positoned up high, you got me to thinking here.

Queston: Aren't the satellites used for GPS geosynchronous?

[SomeSailor]

2850Bounty wrote:
Well, while I still see logic to the antena being positoned up high, you got me to thinking here.

Queston: Aren't the satellites used for GPS geosynchronous?

Nope. Asynchronous. They orbit the earth every 12 hours or so. The reason they are worthless to us boaters is that GPS works by analyzing timing differences between one received signal and another(s). By knowing that a satellite is far away and very low in ascension (it sends it's positional data in the almanac portion of the signal) you get a great triangulation between them. When directly overhead... they are great for altitude calculations, but less valuable for everything else.

If 2D fixes are what you want (us boaters need those... we can guess our altitude) then you wanna predict that satellite rising (in ascension) get on it... and stay on it through the declination of it's orbit on the other side all the way to the horizon.

[2850Bounty]

Mike, as much as we lock horns occasionally, I usually trust your knowledge on this stuff. So thanks for that lesson.

I'd been thinking that we used geosynchronous for GPS. :sorrow:

.