I have a 2004 with the Bose radio. The CD changer and FM reception work fine. AM reception is terrible. Any ideas?
Check to see that the connection plug to the antenna in the trunk (on my '92 about 2 ft from the antenna) is in. If it's connected, disconnect it and see if there's any change. If no change, then look for a bad ground for the antenna (loose, rust underneath the fender preventing a good metal to metal contact).
Originally Posted by Magic Rat
I have a 2004 with the Bose radio. The CD changer and FM reception work fine. AM reception is terrible. Any ideas?
AM radio reception capability is more degraded by antenna and antenna line problems than FM radio reception capability is.
Unlike some earlier year Miatas, the 2004 Miata's antenna line plugs directly into the Mazda Miata power antenna. Also unlike some earlier year Miatas, the connection and the antenna line run in the trunk area is not customarily troublesome. As Keith mentions quot;a bad ground for the antenna (loose, rust underneath the fender preventing a good metal to metal contact)quot; could more likely be an issue for older Miatas, but not so likely yet for 2004's.
For 2004's the most likely culprit results from some welding being done on the car (e.g. for a roll bar installation) melting the coaxial antenna line somewhere along its run. The coaxial antenna line getting pinched and internally shorted while installing something aftermarket is another possibility. A common place for that to occur is under the center console.
A problem with the AM section of the car's radio is of course possible, but a lot less likely than an antenna, or antenna line problem. Aftermarket radios have less radio reception capability that OEM Mazda Miata radios.
Thanks Jeff. Very informative.
I have a lot of stuff running behind the driver's side of the center console, i.e. a thick cable for my engine computer (mounted behind the seat) and your splitter for the CB. I didn't know the stock radio antenna also is back there. Maybe I crushed something.
Long-overdue update: I never got around to diagnosing this problem last summer, or this summer either, but this week I finally installed an aftermarket head unit -- the problem remains -- so at least I know it definitely wasn't the radio! Will check out that antenna wire and stuff ....
New question: my car DOES have a rollbar, although it's bolted in, not welded .... if necessary can the radio-to-antenna cable be easily replaced, or must I buy a whole new antenna assembly?
The antenna cable can be replaced if that's your problem. It's is actually two pieces. One long one that runs from the antenna assembly, along the driver side tunnel, through the center console and to the right of the radio console where it actually plugs into a shorter antenna cable, a few inches in length. Don't know why they did it this way.
I think Keith zeroed in on something with the ground and it's usually at the base of the antenna assembly that might not be grounding well because of a lack of good metal to metal contact. That might be due to rust but that's not as likely as there's simply paint in the way.
I replaced my antenna cable to no benefit but when out of curiosity, I ran a wire from the ground sleeve of the tip of the antenna cable (right at the radio) and touched different different chassis points and even the metal case of the radio. AM reception suddenly and greatly improved which told me I had a ground issue.
This all presumes you're using an OEM antenna or something just as long. If you're using a stubby, all bets are off unless you're parked directly beneath a broadcast tower.
ACB,
Thanks for your insight.
I have the OEM power antenna.
So, when you discovered you had a ground issue, how did you fix it?
PS - on my old NA, I replaced the stock antenna with an S-2000-style stubby, and it didn't hurt the reception at all.
On mine, I was so burnt out, I just grounded the aforementioned wire to the radio's chassis and called it good. On another, I removed the antenna, used a rotary wire brush and cleaned off the surface around the antenna hole inside the trunk.
Your stubby works great in Boston, I'm sure, but not in BFE Montana.
Magic Rat,
Try tightening the antenna mount to assure it's electrically grounded well. If that's the problem, taking the antenna off the car and cleaning all of the electrically contacting surfaces may be more long term effective.
If that's not the problem, unplug the car's antenna line from the antenna splitter and plug the line directly back into the antenna. Then do some ohm meter testing from the antenna line connector for the radio to the antenna mast. Check for proper electrical continuity from the connector's center conductor to the antenna mast, and confirm its outer part has good conductivity to car body ground, and also that there's no conductivity from inner to outer.
Expect less radio reception capability from aftermarket radios.
On this earth a short antenna mast always has less radio reception capability than a full length one.
I have your PM.
Originally Posted by Jeff Anderson
unplug the car's antenna line from the antenna splitter and plug the line directly back into the antenna
Jeff: it's been three years since I installed your splitter, so I forget how it's wired. Does the stock antenna cable from the HU plug directly into your splitter box? I pulled the trunk carpet this week, but (at first glance) it looks like the cable from the car's interior is somehow attached to the splitter .... does it just pull off? I don't want to break it. Or are your splitter and the HU cable mated in some other place, buried deeper in my car, that I forgot about? (Yes I know you're not psychic. )
The antenna splitters that I have seen are nothing more than a Y-cable with a female antenna connector and 2 male connectors. Antenna cable plugs into the female connector and the other two connectors plug into the respective plugs on the Head Unit. I had to use one of these on my 350z with an HD Tuner, to get the MSN Traffic Reporting to work; I have never seen seperate antenna jacks for AM and FM, though. |
Post at 2-7 07:35 AM
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