Garmin GPS Ext Antenna

[Aquaholic99]

I am installing a Garmin GPSMAO 168 combination GPS/Fishfinder. I am using the external antenna. In order to get the antenna above the bimini top, I need to mount the antenna on a 4 ft mast. Now for the problem..<br /><br />The Shakespeare mast I bought has an inside diameter of about 1/4", but the connector that Gramin factory installs on the external antenna is too large to fit through the center of the antenna mast. I can buy a replacement connector, but I am hesitant to cut the cable (which I would need to do in orfer to get iot through the antenna mast).<br /><br />Does anyone have experience with this type of problem??<br /><br />//Aquaholic

 

[Reel Appeal]

Re: Garmin GPS Ext Antenna

Hi,<br /> Don't cut the cable!.You have two options on this.One,get a speedbor(spade)type drill bit a little larger than what you need for the connector and an extension for the bit.Any decent hardware store should have this.I did this method and drilled out the inside w/a 3/4" bit(all the way through) for a BNC loran connector.Second,you can get some white electrical tape and wrap the wire to the mast.Put the wire to the back or inside(where least seen).I have also seen white duct tape.It's out there!Good luck.

 

[Boatist]

Re: Garmin GPS Ext Antenna

Auqaholic<br />If it was me I would not mount your antenna that high. Before you do this try your antenna at a lower postion even under your Bimini top. Put your unit on the page where it shows all the Satellites hook up the antenna and move it to different locations on the boat. I think you will find works just as good even under you bimini top. Try it on top of the horn or on a rail. Make or buy a braket and mount it near top of window. If you mount it up high I do not belive will make any difference in signal. I know mine work just as well under my top. No anchore, dock or fishing lines will ever get caught on mine. Just try it before go to all that trouble.

 

[Paul Witt]

Re: Garmin GPS Ext Antenna

The higher you mount the antenna, the more deviation you will get as the boat rocks. Do not mount it too high. Good luck.

 

[ERR446]

Re: Garmin GPS Ext Antenna

I experienced this same problem with an external antenna mounted on my bow rail for my Garmin 168. I had United Radio take off the connector, thread the coax through the antenna mount, and reinstal a new bnc connector. They have all tools necessary to instal connectors to avoid intermitent and corrosion type problems. Also believe that Radio Shack has this capability. Good luck.

 

[rons boat]

Re: Garmin GPS Ext Antenna

I agree with Boatist. Don't mount the antenna above the top and go for the side. Only when the top is wet would the attentuation thru the canvas even be noticeable on a few of the transponders. A common misconception is getting closer to a satellite provides better performance. Calcultions reveal that it would take a few thousand miles to make a small difference in signal strength. The formula is 36.6 + 20 log (d)miles +20 log (f)mHz. A simple formula is half the distance of 23,800 miles would produce an inprovement of only 6dB.

 

[Reel Appeal]

Re: Garmin GPS Ext Antenna

Hi again,<br /> Forgot to mention.I did away with my 4' extension and got a 1 foot extension with a ratchet type antenna mount(non handle type).Since I leave my bimini up always,I mounted the extension to the vertical frame at the back corner.The antenna itself is only 4" above the top.Tie-strapped the cable down and under bimini into hull,to GPS.Nice clean install,antenna out in the clear w/no obstructions.Just my 2 cents....

 

[Boatist]

Re: Garmin GPS Ext Antenna

Aquaholic<br />You can get antenna extentions that are 1 inch inside. I know West Marine sell stainless steel one that are 1 foot or 2 foot and can screw as many as want together. It is best to get clear view of the sky but at least on my unit a little sunbrella make no difference. At least on my boat more important to have a clean out of the way instaltation than to have it up high.<br />Only important satellite for you to view low on the horison would be the WAAS Satellite for Altantic Ocean region (AOR) at 55.5 degrees West in Geostationary orbit 22,300 miles over the equator at 55.5 degrees West. From your area can not see the Pacific Ocean region (POR) WAAS Satellite over equator at 180 degrees West anyway.

 

[Boatist]

Re: Garmin GPS Ext Antenna

Ron Davis<br />Actually most of the GPS Satellites are in high earth orbit 1200 miles up. (21 plus 3 spares) They orbit in 12 hours. Are two Geostationary WAAS Satelites up 22,300 miles, over equator at 180 degrees West (POR) and 55.5 degrees West (AOR). Only the West coast of the US can see both WAAS Birds.

 

[rons boat]

Re: Garmin GPS Ext Antenna

Boatist, I do agree that most are in low earth orbit and with a little trig probably about an average of 1500 to 2000 miles from the boat most of the time. However, the math still doe not compute even a measureable difference of free space loss difference for less than hundreds of miles. I get amused as a retired microwave engineer at all the people putting there dishes on top of their house where they can't get to them while their thinking is they are: "getting closer to the bird" Off course I realize free space loss is only obtained with an obstruction free path. Those gps birds on the horizon probably would shoot under the canvas most of the time. Who knows, that top we are discussing may be a great radome. Thanks Ron

 

[Capn Mike]

Re: Garmin GPS Ext Antenna

I keep my bimini up all year, and mounted my GPS antenna to the top of my cabin, about 4-5' below the top.<br />It works fine. Boatist is right: you don't need to worry about it, as the signals will pass right through it.<br />In fact, I use a hand held as a backup, while sitting underneath the top. Makes no difference under or not.