XM Radio signal dropouts
 

Hello all:

I've got XM radio in my car. About a month ago, I noticed a drop in signal quality across the board along with complete signal loss quite often.

I've checked the connections in the trunk and they're fine.

There are times when reception is fine, but for the most part, I get two out of three bars on the meter and complete signal dropouts.

Any ideas? It's the original Becker head unit with a Pioneer receiver. I also have La Jolla Audio's direct line connection from the receiver for true CD quality sound. I also don't want to pay Meyer Emco $50/hour to see what's wrong if it's an easy fix!

Thanks!!

Stefano, did you ever figure this out?

Also, how did you install the XM? I'm thinking about geting teh cheap one that loads through the casette. Comments?

Bot

Hey Bot,

No, I haven't gotten my XM radio fixed yet; I simply haven't had the time to take the car over to Circuit City or the likes to have it checked out. Boy, once you've gotten used to XM radio with no commercials, regular radio really stinks. (My CD player has gone on the fritz too....)

I'll update when I get it fixed. Hopefully soon. I have Thursday off. Hmmmm.

As far as the cassette goes, I figure it'd sound fine. As it is, most XM systems simply go through an unused radio frequency, so you're really listening to very good FM reception once the sound makes it to the speaker. So going through the cassette can't be much different. I opted for La Jolla Audio's hardwire adaption of the Becker head unit for true CD quality sound. But since you've got hearing issues as it is, it probably wouldn't be worth the investment.

Good luck and I'll update once I get this taken care of. It's been a couple months now, so I'm VERY ready to get it fixed!

I'm wondering about the possibility of running the XM output into the CD changer output (I don't have the changer installed on my 95 E320) and have it switched on through the head unit CD switch.

Is that do-able?

Anybody?

Also concerning interference, I'm wondering about the satellite signal. Is it a geostationary satellite or are there a constellation of broadcast satellites that the receiver chooses from as they come over the horizon?

There are two geosync'd XM birds, named Rock . . . and, of course . . . Roll, over the east and west coast of the US.

That's interesting and not unexpected.

With GPS signals the many birds aloft send weak signals to Earth and its up to the receiver to decode the identities and match them to the ephemeris. This can get confusing to GPS if there are radio-reflecting surfaces very near the antenna. Then the reflected signals reach teh antenna with slight time delays and if the surfaces are sufficiently reflective it may be the the receiver will fail to lock onto the signal. This is multipath reflection.

I wonder if XM or Serius have a similar problem with multipath? I mean, if your antenna is close to some reflective surface, will the antenna capture multiple signals and the receiver perhaps fail to discriminate the direct signal from the multipath time-delayed signals?

Is there an EE in the house?

Botnst

I had the XM system for a week in a rental in NJ and NY. Driving around Atlantic City, up the parkway and around suburban Montclair, NJ, then the ultimate test, the canyons of Manhattan, the XM signal was very strong and clear. Dropouts occured when stuck in traffic and going under a bridge or overpass at less than 30-40 mph, since the data buffer in the radio wasn't big enough to handle the loss of signal. Of course, the Lincoln Tunnel was a "blackout" for XM, but driving around Manhattan we didn't lose signal once. Have to admit, the "All Elvis" channel was cool . . . for 10 minutes. :rolleyes:

Hey Stafano.

I just started the activation process on my unit and noticed this, in the fine print (quote):

If your antenna was professionally installed inside the car, you will have mutes and other reception problems. Please return to your installer and have them place the antenna on the outside of the car. You should not be charged for this service.

Is your antenna inside?

Thanks, Bot.

No, the antenna is mounted on the topside of the trunk near the rear window. The problem I'm having is less signal (two of three bars on the meter), then the signal begins to dropout completely. Until this situation, I had no problems at all with signal quality with only occoasional dropouts that are normal. I hope to get the unit checked on Monday or Tuesday.

I got the 'thru-the-casette' unit. Everybody who told me I'd find the loose wiring annoying, hold your breath....you're right. It is annoying.

I'm trying to figure-out how I want it set up and where I want the antenna and whether I want to keep it at all, so I'm going to stick with the wire-belching console look for a couple of months to see what I think.

Right-off though, I gotta say the signal is clear and sharp and the sound seems to have a lot more richness to it than normal radio. There are so many bleeding stations that I'm just hopping from one to another sampling each.

I found that if I rotated the antenna about 30 deg off axis from the centerline of the car that I had less drops with the dash mount. Does that sound right?

Oh, its in my 95 E320 with the stock Becker. Also tried it in my kid's 88 300E with a Panasonic CD using the FM input. She had no drops at all.

My car has window tinting. Could that be the difference?

More data.

1. Occasionally as the signal begins to go out, I get an echo-like effect.


2. If I run the antenna through the slightly ajar sunroof I almost never get a signal drop.

#1 I think that may be the multipath signal to which I alluded earlier. I think that problem is insoluble, given the lack of control on the device I purchased ('Roady II'). I'll bet the optimal solution would be to launch another satellite. That wont happen until the profit margin fattens.

#2 Outside of the tinted windows I get almost no signal interruption. What is the material used to tint? I'll bet its metallic.

Sherlock the Botanist

Reception Problem
 

Hi SfloriII,
It's been a while since we talked last. To address your problem I might suggest putting a temp antenna (mag mount type) to test the stength of the receiver. I have one if you need one. What's up with the CD changer?? Let me know if I can help you further.

Cleeve Morrison
La Jolla Audio Repair

www.mercedesradiorepair.net

P.S. For those that don't know, we have been able to interface the sat. radio into the factory units for several years now. Need more info. contact our website above.

Hey Stefano, et al.

I have the cheap XM receiver now (the one that runs through the casette on my Becker). I've been experimenting with antenna placement. I started with the antenna dead in the middle and slowly moved it and rotated it first left then right across the dash.

In the course of this ongoing experiment, I found something that really surprised me: The best reception in the cabin is right against the windshield in fromt of the passenger. Interestingly, this conforms with the placement advice given on another thread (sorry, I can't give credit to the author) in which he'd run the antenna lead under the speaker grill and down through the dash to the XM receiver/decoder.

I wonder if this observation can be confirmed by anybody else? Does the doorpost act as a waveguide? Is there an engineer in the house?

Bot

Hey Guys,

Just to let you know, I did learn what the problem was with my reception.

I called Scott out at La Jolla Audio and he told me that it's likely the Pioneer unit's receiver that has gone bad in my car. It's one of the earlier models and several of his customers have had similar problems with signal dropout.

With his advice, I purchased a new Terk unit which I will try to install tomorrow. I also bought two Rainbow speakers for the dash since one of the Bose speakers is going bad. I'll update when I get the installation done! :)