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October 14, 2005 10:53 AM

I just bought a Sirius satellite radio Starmate receiver and I don't want to mount the magnetic antenna on the exterior of my car.

The radio works just fine with the antenna plugged in to the receiver and sitting on my passenger seat. However, in the event that I have a passenger, I would like to be able to throw the antenna up on the dash (this would probably improve reception, as well). Is their any reason to avoid placing a powerful magnet near the gauge cluster, the stereo, or anywhere else? I have a Saturn Ion with a center-mounted gauge cluster and I would be putting the magnet either on the flat part of the dash right in front of the gauges, or in a little space below the gauges but above the passenger airbag indicator and stereo.

Bonus for telling me how far away I need to keep the magnet from my laptop (which I travel with daily).

posted by amro to technology (8 answers total)

I'm pretty surprised that antenna, which is designed to use a ground plane, is working without one at all. You might find that if you exit the city and go somewhere without terrestrial repeaters the signal disappears.

As for the laptop, I doubt the magnet would manage to erase the hard drive (especially since it should be built into a faraday cage) but stranger things have happened. It'd say keep it at least a few inches away. If your laptop has a 3.5" floppy in it I suppose it could also demagnetise the heads (unlikely but maybe possible). It might also mess with the CD/DVD laser, but I doubt in any permanent fashion. I don't believe there's anything else in your laptop that would be vulnerable to magnetism, but someone else might tell me differently.

I'm not sure about the car, the only things I know is the the gas gauge uses a bi-metallic strip, which, if it uses any magnetic metals, might read improperly.

If you simply don't intend to mount the antenna "properly", why don't you open it up and remove the magnet?
posted by shepd at 10:59 AM on October 14, 2005

While the magnet on the base of the antenna is likely pretty strong to keep it glued to the roof while the car is moving, the strength of the magnetic field diminishes with an inverse cube ratio. In other words, the strenth of the field at a distance of 6 inches is 1/216th as strong as it is at 1 inch.

You don't need to worry about the magnet affecting the gauges. As far as the laptop goes, just keep the maget about 6 or more inches away to be safe.
posted by pmbuko at 11:07 AM on October 14, 2005

I have a similar Sirius radio set in my Honda Civic. I put the antenna back in the rear of the car under the rear window (attached with some of the tape that came with it) and routed the wire back up to the front. It works fine... the only time it cuts out is when the roof-mount would cut out as well (underpass, lots of overhanging trees, etc).
posted by selfnoise at 11:12 AM on October 14, 2005

Another vote for on the rear deck, with the same caveats.
posted by kableh at 12:39 PM on October 14, 2005

selfnoise and kableh, my only fear with that plan is that at some point I'd remove the antenna and have a spot on the rear deck that the sun hadn't faded... But perhaps I can find a perpetually shady spot back there, I will check it out, thanks.

shepd, I don't want to remove the magnet entirely for the reason you mentioned - once I get out of the city, I may have no choice but to (temporarily) mount the antenna on the roof occasionally.
posted by amro at 1:04 PM on October 14, 2005

In the installation instructions for the kit I bought (I have a SIRIUS module for an Alpine deck), they suggested mounting on the trunk lid of the car for "convertibles only". I'm not sure what the logic is with that, and I didnt bother trying it (I have an Audi, and others on AudiWorld had just put their antennas on the deck, since there isn't a seal to tuck the wire under).
posted by kableh at 1:37 PM on October 14, 2005

In the installation instructions for the kit I bought (I have a SIRIUS module for an Alpine deck), they suggested mounting on the trunk lid of the car for "convertibles only". I'm not sure what the logic is with that

The antenna needs a 360 degree view of the sky to ensure it can catch the signal from the satellite (since you won't be turning the car to match the signal).

On a normal car, the back window and roof will cause a deadspot in the 360 degrees view the antenna needs if you mount it on the trunk. So, again, if you need the satellite signal, no luck.
posted by shepd at 3:22 PM on October 14, 2005

I've had no problems w/ my Sirius antenna 'mounted' with a small piece of velcro tape to the upper-right corner of my dash, wedged between the glass and the dash. My laptop sits on my passenger seat often with no ill effects, either.
posted by darknemus at 6:40 PM on October 14, 2005