Antenna interference of different cartopped canoe materials

My Mercedes sedan has a fin antenna on the back of the roof. I have cartopped three canoes made of three different materials on that vehicle. The cartopped canoes of course completely cover over the antenna.



My wood/canvas canoe doesn't noticeably interfere with my satellite radio signal. My Aramid (aka Twaron, aka Kevlar) Nova Craft canoe interferes occasionally with the signal in places where the boatless car would get signal. My carbon/Innegra Swift canoe interferes the most. Anyone know why?

This never happened with the good old-fashioned vehicles with fender-mounted whip antennas (and utilitarian rain gutters), such as my old van in the background.

Another electromagnetic phenomenon is that all canoes cartopped on that vehicle will cause my headlights to come on in the daytime, presumably because the canoes fool the headlight sensor in my rear view mirror housing into thinking it's dark. I describe this problem and my solution in this post and some that follow in the following thread:

Short answer is that carbon fiber is electrically conductive and kevlar is not.

Long answer:


From the link:

"Carbon fiber, as a conductor has been shown to reduce Radio Frequency in cell service as much as 40-60% in specific applications. While many carbon fiber cases look downright amazing, it is not the best choice for a composite material in phone protection. However, the use of Kevlar (aramid) protection in cell phone cases poses a better option as Kevlar is not a conductor of electricity. Kevlar holds similar strength properties as carbon fiber and absorbs energy better as it is not as stiff as carbon fiber."


For the lights, yes, that is likely just the daylight sensor being fooled by the boat shadow.

My carbon fiber canoes absolutely do diminish satellite radio reception when travelilng in areaas where I do not otherwise have the problem, either with bare roof, wood, or with Kevlar. Quite annoying on longer trips, but there is nothing I can do about it.The conductivity of the carbon presumably acts lilke a shield or attenuator at the radio frequency of the incoming signal.

Glenn MacGrady said:

My wood/canvas canoe doesn't noticeably interfere with my satellite radio signal.

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Well, there ya go... one more reason to paddle only wood/canvas canoes!

You may find that the 'shark fin' on the roof is for satellite communication and that the ordinary radio antenna is provided by wires in the rear window(s). These may look like heater wires but they never warm up. This is how my car is configured. Both will be impacted by having a large carbon Faraday cage on the roof. This is one more reason to use wooden canoes as Patrick mentioned.

Benson

Too bad you're not into aluminum canoes. With a little wire and a couple alligator clips you can turn it into a great antenna.

lowangle al said:

Too bad you're not into aluminum canoes. With a little wire and a couple alligator clips you can turn it into a great antenna.

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Yeah, as a side benefit it may also make a great lightning rod.

Interesting. I doubt that I'd have ever noticed as I almost never have the radio on but interesting nonetheless.

(all due respect to @Patrick Corry but, although I suspect that I will someday tackle a w/c restoration, interference with radio reception will certainly not be a consideration)

Gamma1214 said:

(all due respect to @Patrick Corry but, although I suspect that I will someday tackle a w/c restoration, interference with radio reception will certainly not be a consideration)

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And when one gets old enough, lifting a w/c (or any heavy) canoe onto a car becomes impossible or dangerous. Then a trailer must be bought. Use that trailer . . . and Voila! . . . no more blocked antenna reception problems with any canoe.

Ergo: Getting old has canoeing benefits.

Q.E.D.

I was concerned that the canoe would block the ez-pass link when going through a toll but haven’t noticed a problem yet.
Jim

Elon Musk better test his upcoming satellite cell phone service with phones that are inside cars having carbon canoes on top. I mean, if I'm passing Porsches on the Autobahn with a carbon fusion canoe on top, I want to be able to text uninterrupted with my boat poling idol Sofia Costanza Brigida Villani Scicolone at any of her homes around the world.

Benson Gray said:

You may find that the 'shark fin' on the roof is for satellite communication and that the ordinary radio antenna is provided by wires in the rear window(s).

Click to expand...

I think you're correct, and I believe you can see the rear window diagonal antenna wires in the picture in my OP.