Garmin GMR 41/Routing/EMI Shielding

[mmitchell]

Two Questions for a 2006 25' C-Dory:
Per the installation manual they do not recommend cutting the cable from the radar to the GPS. Garmin does require to drill a 1.25" hole for routing the cable. We have a arch on the roof and would like to route the cable from the aft of the cabin
1. Has anyone routed there cable this way?
2. Provide any web site on EMI shielding as 1 1/4 conduit is out of the question.

Thanks

[Gene Morris]

mmitchel;

We have the same radar on our Tom Cat. The cables are run through the radar/rocket launcher tubing. The cables are routed through the head then to the 3210 forward along the top of the cabin. This seams to be a good installation. The only problem that I am having is intermittent interference with the Icom 504 vhf which is routed on the port side of the cabin.

By the way, the 4kw radar is magnificent compared to my old simrad 2kw unit.

Gene

[thataway]

I don't know if this would work in your arch or not, but with another boat, we ran the cable inside of the arch framework to where it bolted to the cabin. The center of the mounting plate was cut for the cable to pass thru and then a hole in the cabin top cut right under this hole. Thus the cable was routed directly into the 1 1/2" tubing of the radar arch, and then into the cabin. I would not consider metal conduit inside--not necessary. You might consider threading the radar cable down the foreward wall of the head, under the galley, up under the counter, and to the back of the Garmin Display--don't know if this would help with interference or not. Normally Radar does not cause VHF interference--but with modern electronics--who knows? As noted elsewhere I solved my EMI with ferrite beads.

[mmitchell]

Thanks for the great ideas. I would love to run the cable through the arch as that is how we ran the vhf and gps cables. It give it a very professional look. That is one of my questions as the connectors on the end have been attached through the factory. Not sure if it can be dis and re- connected? Have you had good luck with the ferrite beads and where do you locate them on the cable?

[Butch]

Here is a rather inexpensive idea to attempt to eliminate EMF interfearance on electronic devices. It works for me on my ham rig and mobile radios. Place ferrite chokes (filters) around the signal lead cables and the power cables as close to the electronic devices as you can. Ferrite cores come in many sizes and configurations. You can get them off the net.

If you are not familiar with ferrite chokes... take a look at you computer and most USB cables... you most likely see little cylinders wrapped around the cable and of the same color of the cable. That is a ferrite choke.

Try it and let us know how it works out...

Butch

[thataway]

As Butch relates the Ferrite beads (chokes) is simply a hollow bead or cylinder made of ferrite, which is a semi-magnetic substance made from iron oxide. There are different materials and different sizes and allow from one to a number of passes of wire. You split them open and put over the power and signal cables. Some folks advise not to put on the vHF antennas, in fear of supressing the signal. I have tried measuring output with a bead over the antenna, right by the PL 259 and removing--no difference in RF output. Basically the ferrite material helps to prevent excessive Electromagnetic interfference or Radio Frequency Interference.

You want to put the ferrite beads as close to the case as you can get them. I had a few in my junk box--and I got a enough more from the local electronics shop for a couple of bucks. Theirs were left over from installs. There are multiple sources of ferrite beads on the web. Be sure and specify the size of the cable you are covering--the bead needs to be tight on the cable. There are different types of material for supression of the various frequencies. If you are working with a depth finder cable you might want to use type 43 or 44 material; for VHF radio frequencies type 73 material.