Adding 2nd VHF antenna

[Tuna Man]

My 2006 Marlin came with a inexpensive Standard VHF connected to a inexpensive Shakespeare 8' antenna . The antenna is mounted on the stbd. side of the 'hump' on the hardtop, towards the front. In addition there is a small Furuno GPS antenna mounted on the port side of the hump on the hardtop, also towards the front. The Furuno 42" open array antenna is mounted in front of the hump near the front (centered). Finally the mast light is on the hump about three feet behind the leading edge.

I am about to add another 8' VHF antenna (Digital brand) to the hardtop with another SS mount. This antenna will be connected to a Icom 504 VHF. I prefer to keep the antenna wire in the electronics box (towards the front of the e- box). However, I do not want any interference with the other electronics.

Where do you guys recommend I place the second VHF antenna? Is there a standard to keep antennas away from each other?

 

[NOTHING ELSE MATTERS]

GPS instructions say antenna should be 3 feet away of anything. What i would do is get a 1 foot or 2 foot extention and mount the GPS antenna behind the radar(make sure the GPS antenna is clear of the radar path) and then mount the second antenna where your GPS antenna is now.

 

[BobP]

You could probably mount the GPS antenna on a low mount since the open array active elements are above the motor base, and the array window vertical is 12.5 deg down off horizontal, so it will miss a low mount I bet.

If your position selected is beyond where the box below is, route the wire along the top side of the hardtop in a continuous bead of silicone, with an occasional clamp. Denatured alcohol clean everything first, silicone will hold wire very well. Routing wire on bottom side doesn't look nice at all.

 

[CJBROWN]

Just to confirm your hardware, I really like my 8' glass Digital antenna. Was happy I went that way on other forum recommendations. Mounts on a SS swivel to fold down for trailering.

With my Icom 503 I easily get out 30 miles, clean and clear. Couldn't be happier.

 

[Tuna Man]

Gents,
I like your ideas. Currently the light mast is centered on the roof (left to right) and clears the radar by two inches or so. Do you suggest leaving the light in place and positioning the GPS antenna three feet aft (towards the back of the boat)?

I am photo posting impaired. I have a photo of the roof of the hardtop and would love for someone to post it for me. If you can post pics send me an email at scottsecor@comcast.net and I will send you the photo to post.

Thanks again.

 

[BobP]

I diasagree with NEM, I would not see the need to apply the 3 foot rule unless in the radar's aperture, if you are down by the array's motor base (you said you had an open array, correct?) and the GPS and radar works fine (duct tape it there and go for a ride full electronics on), then it will all work out.

The 3 foot rule never made sense on pleasure boats, because anything in a hard top box would be too close so iteh box couldn't be used. ie, my GPS head unit and mulitfunction display is in box, with radome inches away on top of hardtop.
Perhaps if someone had high power commercial radar, high power short wave radios, then it makes sense, but they don't know what you have so have to assume worse case.

Look at the wheel houses of the Deadliest Catch boats, look how much equipment they have, no way any of it is 3 feet apart.

I'd leave the light mast alone, and off set from the centerline the GPS antenna on the lowest mount you can find, and go a little back from where mast is, say 6 inches to a foot, you will be clear of the beam, going back further you may not then stay more than 3 feet back.

If you put the GPS sensor up on a pole, you will also need a folding base, I prefer to minimize the parts needed and exposed cabling it get it done.

Make sure the light pole and any other pole/antenna can lay down w/o interference for your selected locations/relocations before you start boring holes. silicone everything, hardtop is balsa cored.

No such thing as XL Balsa.

 

[NOTHING ELSE MATTERS]

BobP, the 3 foot rule is not mine, is in every GPS installation manual i ever installed. And YES, there is a difference between too close and 3 feet or more apart. You will never see the difference unless the rock you mark on your GPS last year, you run over it this year and scratch your head why? (rock never moved), the signal is getting interferance and does not read 100% your position. What i just said is a little over-rated but you get the idea.

 

[CJBROWN]

Posted for Scott; roof of his marlin: