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TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

Sunroof and antennas...

Damnit, why did I get a car with a sunroof (2006 Mazda3 hatch w/ sunroof)?

Of course, the best place to install an antenna is the middle of the roof of the car.

However, the sunroof and its mechanism prohibit the installation of an antenna anywhere on the front two thirds of the roof.

This leaves the back portion of the roof. Not a bad compromise, right? Well, that's where the factory car radio's FM/AM rubber ducky antenna happens to be mounted!

I could install it off-center a bit, however it would only be about a foot away from the other antenna, which is probably not good. I assume, even though the car radio's antenna is not quite the same band, that considerable RF energy would be picked up enough to possibly damage the car radio receiver?

This leaves a couple of options:

A) Get rid of (or relocate) the factory AM/FM antenna and install the 2m antenna in its place.

B) Come up with a filter of some kind to install in-line with the car radio antenna to protect it from the undoubtedly high levels of RF that would result from two antennas a foot apart.

Toughts/ideas/recommendations?



Gbcue
Premium
join:2001-09-30
Santa Rosa, CA
kudos:8

Glass mount?



DrStrange
Technically feasible
Premium
join:2001-07-23
West Hartford, CT
kudos:1
reply to TheMG

How about this?

»opektech.us/product/am-204-7c-tr···p-mount/

FWIW Mazda fixed your problem in 2012. They got rid of the rubber duck on the 3 and put the broadcast radio antenna in the rear window glass [and, oddly enough, it gives great reception on both bands].


TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel
reply to Gbcue

said by Gbcue:

Glass mount?

Everything I've read about those said that they leave much to be desired and to avoid them if at all possible.

Up here, repeaters are far and few between so I don't want to make too many compromises when it comes to antenna performance.

said by DrStrange:

They got rid of the rubber duck on the 3 and put the broadcast radio antenna in the rear window glass [and, oddly enough, it gives great reception on both bands].

I wonder if I could get an aftermarket antenna to stick in a window similar to what they've done on these newer model years?

How do those compare performance-wise to a roof-mounted antenna?

mr weather
Premium
join:2002-02-27
Mississauga, ON
reply to TheMG

What about something like an NMO L-bracket mounted in the gap between the hood and front fender?
--
"It's all coming down!!" - Mike Holmes



aSic
application specific
Premium
join:2001-05-17
Wakulla, FL
Reviews:
·Comcast

1 edit
reply to TheMG

Lets look back in time. Here's my answer from so long ago.
»Re: mobile antenna for 2m/70cm

I was very happy with it overall. Stayed on there long after I sold the car. The whole thread rather than just my clippings has some useful discussion.

edit: in addition, I would suggest a Comet CP5-M lip mount on the hatch with the aerial of your choice. I also did that with my old Subaru, on the drivers edge, towards where it meets the bumper (vertical), and it performed excellently. Pretty sure I photo'ed that and posted it in here somewhere too.
--
Teamwork is a lot of people doing what I say.


mocycler
Premium
join:2001-01-22
kudos:1
reply to TheMG

I say mount the antenna where you can on the roof and don't worry about the factory AM/FM antenna.

The car receiver will not be damaged. A 2-meter radio is, what? Fifty watts? Maybe 100 on the top end? That's not even close to being a problem, especially with the filtering qualities on new receivers.

I've been running a 75 watt FT-2900 in my truck for years. The proximity of the 2-meter antenna to the AM/FM was never a consideration. I've had zero issues.

Cross-resonance and receiver overload isn't an issue until you hit much higher power (like a 1000 watt linear) or if the receiver and/or transmitter are not well engineered in the first place.

I'm looking for a solution to put an antenna on my Jeep. It has a full cloth top so a roof antenna is totally out of the question. My options are few. I'll probably go with one of those antenna mounts that go on the tail light or spare tire rack. The ones that go on the front fender/hood I think look goofy.


CXM_Splicer
Looking at the bigger picture
Premium
join:2011-08-11
NYC
kudos:2

said by mocycler:

I say mount the antenna where you can on the roof and don't worry about the factory AM/FM antenna.

Agreed. The center of the roof is technically the 'best' place but you probably won't have a noticeable difference anywhere on the roof. Since you have a large hole in the metal replaced with a piece of glass, the whole 'middle of the roof' idea is kind of out the window anyway; just get as much metal under the antenna as reasonably possible and you will be fine. The worst possible location (from a ground plane point of view) is a trailer hitch mount yet I see them all the time and people still make contacts.

moonpuppy

join:2000-08-21
Glen Burnie, MD
reply to DrStrange

I have that mount and it is crap. Won't ground properly.



Hank
Searching for a new Frontier
Premium
join:2002-05-21
Burlington, WV
kudos:2
Reviews:
·Frontier Communi..
reply to TheMG

I have a Subaru Forester with sun roof, although I probably have more metal surface area than your Mazda3 the antenna is mounted within 1 foot of the AM/FM antenna. I do not experience any interference or overload with this arrangement.
I used an Larson with NMO mount.


TheMG
Premium
join:2007-09-04
Canada
kudos:3
Reviews:
·NorthWest Tel

said by Hank:

I have a Subaru Forester with sun roof, although I probably have more metal surface area than your Mazda3 the antenna is mounted within 1 foot of the AM/FM antenna. I do not experience any interference or overload with this arrangement.
I used an Larson with NMO mount.

Good to hear. I just wasn't sure exactly how robust the receiver front-end in typical car radios are nor how much RF power would actually be picked up by the out of band FM broadcast antenna.

Maybe I'll go ahead and mount it on the roof about a foot away and see how it goes. Thinking of picking up a 5/8 wavelength 2m antenna with NMO mount. Won't be right away though, as it's in the -25 to -40 degrees celsius outside and I do not have a garage nor does anyone else I know. Don't want to mess around pulling off trim inside the car in the cold as there's a high risk of breaking something (plastic gets very brittle in such cold temperatures).

Thanks for the info/suggestions everyone!


Sr Tech
Premium
join:2003-01-19
Valhalla, NY
kudos:1
reply to Hank

said by Hank:

I have a Subaru Forester with sun roof, although I probably have more metal surface area than your Mazda3 the antenna is mounted within 1 foot of the AM/FM antenna. I do not experience any interference or overload with this arrangement.
I used an Larson with NMO mount.

Same here but different car.