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Discussion Starter #1
Big big delay ....... but finally, here it is ..

When i bought my used car, the SL antenna was already installed. FM reception was very very bad. No secret : a small antenna gives bad reception.


I've decided to extend the antenna in the rear bumper using a simple cable. Even if it's not "perfect" (based on radio reception theory), the result is good enough for me (FM reception).

The idea is to add a new antenna, which is connected on the antenna amplifier. This connection is done inside the amplifier itself : the new antenna is soldered on the main PCB. Therefore, some electronic skills are needed (at least to be able to solder a wire on a pcb).
Of course, the amplifier warranty is removed ..

A) The antenna amplifier is located in the rear left side of the trunk (See "Open side trunk paneling" thread)


B) Disconnect all the cables (3 for Europe as we haven't Teleaid system). The connector from the antenna is difficult to be removed.


C) Remove the bolt of the antenna amplifier and remove it from the car.

D) Unscrew the two screws on the amplifier, and open the box


E) i've used the teleaid connection (which is empty in Europe) as a hole for my new cable (C) (Small Antenna coaxial cable). The shield of the cable is soldered on the PCB ground (B), the hot wire on the FM antenna connection (A).
Final touch, some epoxy glue (D) is added in order to secure the cable


F This new cable goes out of the car through the left ventilation opening (below the amplifier itself (the new cable is shown in green in the following pictures)


G) To go further, the rear bumper shall be removed (i've made a thread on how to remove the bumper).
Outside the car, there is a connector between this new cable and the "added antenna". The added antenna is a wire, 3 meters lenght which is glued on the internal side of the bumper. This is a simple copper wire (not shielded and no need to be big). The only important thing is that the end of this wire shall not be grounded (shall not touch the metal part of the car itself). The cable goes from left side to the right side of the car on the top of the bumper and from right to left.




I hope this explanation is clear enough.. If not, i can add some precision or bigger pictures.
The result is good enough for me : good FM reception as well as TMC channel.
It was easy thanks to the fact that Teleaid system is not installed (no hole was needed in the amplifier housing).
As an alternative (if the teleaid system is installed and you do not want to make a hole or solder somethning in the amplifier), the cable from the amplifier to the antenna can be cutted and connected to this new antenna.
 

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thanks for the tutorial Michel thats the sole reason why I kept the stubby antenna that is on my car, I like to listen to the FM stations such as Jazz, Pop etc.
 

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Very good info and tutorial Michel. It looks "do-able".

Merci beaucoup de votre aide :tu:
 

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Discussion Starter #4 (Edited)
Some additional info : at the beginning, my aim was to replace the antenna.
Therefore, i've tried to find the antenna connector (the black FM antenna on my pictures), without any success.

If someone is able to find this connector, it will be the easyiest way.
 

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Don - Founding Member #4
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:tu:Michel - EXCELLENT information. Thanks for a great idea and the information to complete.
 

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Don - Founding Member #4
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Some additional info : at the beginning, my aim was to replace the antenna.
Therefore, i've tried to find the antenna connector (the black FM antenna on my pictures), without any success.

I someone is able to find this connector, it will be the easyiest way.
:confused:Michel - prior to your original thread, I thought about replacing my factory antenna with either the SL antenna or the black R170 antenna. My thought was to either replace the antenna and base going with the SL antenna and base and then take the old factory antenna and base, plugging it into the antenna amplifier, leaving the SL antenna for show only or splicing the two antenna cables together and then connecting to the amplifier. I could do the same thing with the R170 antenna, as I would have to order the R170 antenna and another factory base which should include the cable that attaches to the amplifier. I would then mount the factory antenna somewhere, either in the trunk or the rear bumper cover. I held off once I read your solution. Is there any merit to what I described or should I just add some wire, soldered to the amplifier circuit as you suggest? Would using insulated wire lessen the reception? Thanks for your help.Y)
 

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Discussion Starter #7 (Edited)
Don,
Your suggestion to use SL antenna only for the design (disconnected) and to connect another antenna to the amplifier itself is ok (and maybe a very good and sympliest solution : no modification of the amplifier, can be reversed, ..).

However, you should find a suitable place for this another antenna.
Some important points :
a) antenna shall not touch metal part (very important)
b) antenna should be vertical as much as possible
c) every metal part around the antenna will act as a shield (i.e the antenna will not receive anything from this direction) : example : if you put the antenna in the trunk, if the trunk is open, antenna will receive. If the trunk is closed, no reception (or bad reception). Therefore, you will not be satisfied with your idea to put this antenna in the trunk.
d) antenna basis should be connected to car body

Point a) is mandatory.

Personnaly, i would go for this antenna in the bumper (see my picture), on the rear left angle, Upside down (it should be easier for the cable) :
- point a),b) will be ok.
- For the point c), at this location, the antenna will have some directivity (antenna will be able to receive signal from emitter located in the rear part of the car, and it will be more difficult for an emitter located in the front right side of the car (all the car will act in this case as a shield between emitter and antenna. However, in suburbs or city, impact may be neglictible)
- point d) will not be done



The result in this position shall be much more better than the SL antenna. You can try it easaly : connect your new antenna to the amplifier, and use adhesive tape on the external side of the bumper (with removing it). You should be convinced with a short run that it is ok.
 

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Discussion Starter #10
Don,

For radio point of view, antenna is OK.
The cable will be ok also (Extension cable lenght will reduce signal strenght, but i dont think it will be a problem)

This is a amplified antenna : you will need also to power it (+12v)

My worry is on the windshield itself : This kind of antenna is forecasted to be installed on the internal side of the windshield. Since few years, OEM windshield includes some metallic coat to avoid too much heat in the car (act as an heat insulating). But this coat acts also as radio wave insulator : In this case, the antenna can not be installed here (bad reception).

Dan, is the SLK windwscreen is "athermic" (i don"t know the exact word in english) ?
 

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Don - Founding Member #4
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:(I finally had the time to install the auxiliary antenna this past weekend. It's the aftermarket 12v amplified antenna pictured in post nine above. I followed Zeiser50 instructions and the install was simple. Using the amplified antenna required as 12v source. Initially, I was looking for a switched power supply and realized that I needed the antenna "on" all the time for the extended range of the SmartTop module. I used the power supply on the antenna amplifier itself. I used double sided tape and mounted the plastic antenna vertically to the flexible, non metallic piece of the left rear bumper cover. Overall installation was simple. Initial results were positive, I noticed a marked improvement in AM-FM radio reception. The downside, no increased range when locking and unlocking the car. I checked from all angles and still no change over the single R170 short antenna. I thought about it overnight. My main concern was the slight battery drain over time from the amplified antenna. With no improvement in range, I removed the antenna and wiring. I can live with the reduced range of the R170 antenna or install the factory antenna. Thanks to Zeiser50 for a great idea and detailed instructions.
 

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Makes me wonder...perhaps the amplifier isn't boosting the frequency that the alarm works on? Or is that a seperate connection?
 

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Discussion Starter #14
Don,
The remote control signal is received by the antenna and extracted using the original amplifier Box.
In your case, i think that the amplifier integrated into your new antenna is not designed to allow frequency from the remote control (probabluy outside the fm/am frequency range).
Have you tried using a simple wire connected to the oem amplifier, in replacement ?
 

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Don - Founding Member #4
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Don,
The remote control signal is received by the antenna and extracted using the original amplifier Box.
In your case, i think that the amplifier integrated into your new antenna is not designed to allow frequency from the remote control (probabluy outside the fm/am frequency range).
Have you tried using a simple wire connected to the oem amplifier, in replacement ?
:)Michel, thanks for the explanation. As with most things, once you done it, it's easy. I could try the wire antenna as you suggested and it wouldn't take long to complete. I was unhappy with the prospect of a small, but constant power drain with the amplified antenna. Prior to the install of the amplified antenna, I tested the factory antenna vs the R170. The factory antenna had at least twice the range of the smaller R170 antenna. Michel, how would rate (range) your wire extension antenna in unison with the R170 on your SLK, compared with the factory antenna? Thanks for the info.
 
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Don,

For radio point of view, antenna is OK.
The cable will be ok also (Extension cable lenght will reduce signal strenght, but i dont think it will be a problem)

This is a amplified antenna : you will need also to power it (+12v)

My worry is on the windshield itself : This kind of antenna is forecasted to be installed on the internal side of the windshield. Since few years, OEM windshield includes some metallic coat to avoid too much heat in the car (act as an heat insulating). But this coat acts also as radio wave insulator : In this case, the antenna can not be installed here (bad reception).

Dan, is the SLK windwscreen is "athermic" (i don"t know the exact word in english) ?
Hey mate sorry i missed this, the SLK windscreen does not have any IR protection
 

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Discussion Starter #17
Don,
Well, i can not answer, as i never made this test (in fact i was more interested in radio performance).
I will do it today or tomorrow : what is the max distance for the key, with my simple wire in the bumper.

Dan,
Thanks. In this case, the antenna can be installed inside.
 

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Thank you for this very useful post to me !

However, I am having issues disconnecting the antenna connector (cable 3) from the box. Is there a specific method or tool to do it ?
Could you post pictures on how to unscrew this connector ?
 
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