Aries,

So, in other words, remove the blue connector off of the Mercedes Sirius antenna and replace the Terk's splitter's mustard one with the blue one??
Have you done this yourself? I'm wondering how easy it is to remove these connectors without breaking them?

Thanks for the info.
Martin-

 

To Jmartinacevedo

I am not aware of any extra adapter that my installer put in, if he did. All I know is that he put the MB factory Sirius radio, XMicro antenna, and programming the Command module for a package price. The antenna is so small that it is hardly noticeable.

 

Yes. If you look at the mustard connector in the picture, there you will find a white locking insert. Just pry that carefully and the jack will release.

 

Thanks for the info guys. Aries, have you ever put an xm antenna in an MB sirius module? I wonder if you still would need the "Y" adapter?

Paulhu is right; the xmicro is really small and certainly much easier to camoflage than the sirius terk antenna with its long tail...

Martin-

 

There is a reason why the XM antenna is smaller than the SIRIUS antenna.

It would NOT be my recommendation to use an XM antenna on a SIRIUS receiver. Both services fall under the satellite S-band frequency table... which has the following specs:

XM Radio: 2332.50 ~ 2345.00 MHz
SIRIUS: 2320.00 ~ 2332.50 MHz

Though these frequencies are really close, antennas are designed to be tuned to their median frequecies (XM = 2338 MHz, SIR = 2326 MHz). So if you use a 2338 MHz antenna on a 2320~2332.50 MHz receiver, you are off target by 5.5 MHz. It may not mean much, but your antenna gains and overall reception are impacted.

Keep in mind that your better cordless phone operates at 5.8MHz or 2.4MHz, from the old 900 MHz - so you can see how much different a frequency change can impact overall performance of a wireless device from within a 5.0 MHZ range.

If you also look at the spec sheets of you SIR antenna, the typical gains from the satellites are about 4db, while the XM antenna only has a gain of 1db.

This information is a general rule for RF transmission. The digital signals always have a better result because of their IF decoders, etc. It is only a guideline.

 

Thanks! - I'll stick to the Terk SirMini-
Martin-

 

Although your general statement of not using the XM antenna for SIRIUS or vice versa is true, the "facts" that you use to arrive at your result are completely bogus.

First of all, cordless phones do operate at 2.4GHz and 5.8GHz, so the frequency difference from a 900MHz phone is really 1.5-5GHz, not 5.0MHz. A difference of 5.0MHz is trivial in most cases. For example, look at FM broadcast range, which in the US is 88.0 - 108.0 MHz, a 20MHz range which uses only one antenna.

All this is really overgeneralization though, so to use these examples without any sort of qualifying reasoning is again, bogus. Note that a all else being equal, higher frequency signal in this range will not penetrate through objects as well as a lower frequency. When would you notice a difference? Well, cellular phones operating at 800-900MHz will outperform phone operating at 1800-1900MHz, at least in structure penetration. What does that tell you about those "newer" cordless phones?

As you correctly stated, the antenna tuning difference, it does not mean much, but the overall performance is impacted.

But earlier you state to go ahead and remove the green FAKRA housing and install the blue, and connect the SIRMINI directly to the receiver. This will have a far greater negative impact on performance than simply using an antenna that is tuned 12.5MHz off. There is a reason the differently color coded FAKRA connectors are used, to ensure that proper connections are made. Since we're talking about the terrestrial portion, there will be a limited impact, unless you're in an area with repeater coverage... at which point it may cause various issues with interference from outside sources (I seem to encounter this in the SF Bay Area and Southern California; someone in rural Idaho probably would not have this issue).

If you don't use the proper connections, yes, it may (or will) work, but the overall performance is degraded.

Therefore, I do not endorse using such an antenna. If you search through the archives here you will find posts explaining my reasoning and also the testing I've done and why I stick with the OEM antennas.

-s-

 

Scorchie, I've seen pictures of your install in this forum where the MB antenna is inside the back glass against what looks like the arms that operate the power rear sunshade. Do you have reception problems with this install or is just as good as the exterior trunk mount the MB prefers for the e-class?

 

Scorchie: The cordless phone example is just a demonstration of how much a slight shift in frequency can make a device better (or worse). It was not intended to relate the satellite radio to such a device. Also take note that I did have a clause pertaining to digital and analog quality.

The XM relies on a lot of terrestrial repeaters with 1 geo-stationary satellite above earth. On the other hand, SIRIUS has 16 satellites orbiting the earth in an atom-like pattern, and 3 of them are up in the United States aerial topology at any given time. SIRIUS for that matter, also has less terrestrial repeaters which means that the receiver's reliance to land-based repeaters are mainly for auxiliary reception only.

This is also the main reason why XM receivers still have signal while their antennas are inside a house or a garage. SIRIUS completely loses signal once their antennas lose the view of the sky.

Since you mentioned SoCal, SoCal has the worst SIRIUS terrestrial reception that we are told of.

So to cut the long story short, the blue FAKRA connector (terrestrial) only makes up a smal portion of the signal that the SIRIUS receiver gets. For as long as your satellite antenna is tuned closer to the dead frequency, then most of your SIRIUS terrestrial signal is fine for your receiver (for as long as you have a view of the sky).

Lastly, a concealed antenna behind a glass as suggested here is about -1db in overall satellite signal quality. The TERK-Mini gets about +2db in our real world tests. Also, you need to have a 90-deg metal ground plane (car body) relative to the antenna's vertical to get the best possible signal.

Again, this is just another generalization of technical details.

 

I emailed my dealer about a Sirius sat install, and he wrote back that they no longer drill a hole in the trunk. Rather they attach the antenna with magnets. Does anyone have any more details on that type of install?

 

I'm gonna have to go ahead and disagree with you there. Actually, I am gonna have to say that in my opinion, you have about the worst information posted to these forums. Nothing personal.

First of all, you say a "slight shift" in frequency? The cordless phone example is a shift of nearly 5GHz, which is 5000Mhz, not 5.0 Mhz like we're talking about... a factor of 1000. That's not even slight...which was my original point.

Secondly, SIRIUS does not use "16 satellites orbiting the earth in an atom-like pattern"... you are confusing GPS satellites with satellite radio. SIRIUS uses an elliptical geosynchronous orbit, so although the satellites move in the sky (relative to a ground observer), the satellites appear in a retrograde movement and do not leave the sight of the ground station. SIRIUS only has 4 satellites, 3 in orbit at the moment, and a spare in storage in Palo Alto (10 minutes from the scorchiehaus).

Although not totally pertinent, you also mistake the XM constellation as being a single satellite... XM has two satellites (named "Rock" and "Roll") in geostationary orbit, meaning their position in the sky should never change, until the 3rd (scheduled for 2004 launch) and 4th (not yet procured) satellites are lauched. The 3rd and 4th satellites are being launched only because the Boeing 702 satellites used for Rock and Roll have a serious design flaw and thus only have a design operational life of six years. (SIRIUS satellites are Space Systems Loral devices and are not subject to this flaw.)

For those that predict the demise of SIRIUS and success of XM, these future costs will figure into how the actual competition plays out.

And, the problem with the terrestrial signal on both SIRIUS and XM, is that if you receive an overload of terrestrial signal (more common in urban areas), it will affect your reception as the earlier receiver designs (of which describes the MB unit manufactured by Delphi) did not have good rejection of these signals, which was the whole reason of the ALC add-on.

-s-

 

By my measurement, the antenna mounting under the deck receives about 2-3dB signal reduction from a trunk mount. I have started using a different OEM antenna which gives about the same performance. The location at the very center rear of the deck seems to give a good view of the sky. The drops outs here are only slightly higher than my friend's Discovery with a roof mounted magnetic antenna.

So, no, it is not as good... but it is good enough considering the improvement in external aesthetics. I find that using an aftermarket antenna under the glass with a splitter and ALC causes more signal degradation (about 6-8dB down) due to the increased number of connectors used. This can affect reception even more.

-s-

 

Although I have the XMicro antenna receiving Sirius satellite stations, I have not experienced any loss or degradation of signal at all, except when I go inside a tunnel, or on rural roads with trees on both sides blocking view of sky. Most of my driving is on highways with an open view of the sky, the XM micro antenna is working fine so far for my Sirius satellite radio.

 

It can vary widely depending on your geographic location. Since you are located closer to the equator than many other people, it helps reception. Also you do not indicate where your antenna is located on your vehicle.

Without any of these qualifiers, your "works for me" scenario may not apply to others.

Also, how do you know your signal is not degraded? Have you measured the signal level with an OEM antenna vs. what you have now, in the same situations? If so, that's fine. But if not, then just because it works does not mean there is no degradation. And depending on someone else's location and other factors, it may make a difference.

-s-

 

S,

1-Is the "other OEM antenna" that you make reference to in your post the one for the CLK/CL? Is that the one that costs over $200?

2-All things considered, what would be worse in terms of signal degradation: (a)switching the blue and green connectors between antennae (as Aries suggested) or (b) simply "forcing" the green connector of the splitter into the MB sirius receiver (as others have done)? About the same?

Martin-

 

Yes, the CLK cab antenna... it is over $250, but I now can get it with the kits for about $75 so I am recommending this route.

Switching the connector or forcing it on will do the same, as it will be missing a component and still have extra connectors in the signal path. The spec sheet for most of the connectors indicates quite a bit of loss per connector at the frequencies used by the satellite radio.

-s-

 

When I say 'it works fine for me", I mean ONLY for me, may not be for others. We have human ears, not dog ears. So I can only say "fine for me" based on what I hear, not based on any instrument's measurement. When I drive my car, I don't need to care about which piston goes up first, which piston goes down next. When I use my computer, I don't care about the CPU speed is processing at 3.2GHz or 3.0GHz. When I take pictures with my $3200 Nikon D2h camera, I don't worry about how many Mega Pixel the picture resolution is. If we were to measure everything in life with instruments, such as weigh our food before every meal, tune our Hi-Fi system to the precise acoustics before we insert a CD, or making sure that our ECU in the car is doing the proper thing, we would feel miserable in life. If the music sounds good to my ear, it does not matter whether I have a $10,000 stereo Hi-Fi systemor $1,000 stereo deck. There is nothing wrong with being precise and technical about electronics and instruments, but life is dynamic, so let's enjoy what God has given us (3 Mercedes, 1 BMW, and 1 1986 Rolls Royce Silver Spur).

 

You didn't say "it works fine for me", I said "it works fine for you". You mentioned something about signal degradation, which I was curious how you measured it. Now I know you didn't. That's all you had to say was, "it works fine for me" instead of pointing out you had no signal degradation.

I was curious about your signal degradation, and if you had actually measured it, I was interested in the results... thus my question.

Please feel free to check your earlier post.

-s-

 

I must agree with you Scorchie! Thanks for the clarification and correction... I have confused the satellite info with others... I was responding to another post in another board about GPS and over there I posted the XM/SIRIUS info. I had both information reversed on both boards!