Technical Comments and Response

FCC ID: RS2X2G100

Operational Description

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FCCID_715706

October 5, 2006 RE: XM Satellite Radio, Inc. FCC ID: RS2X2G-100B For the following information, in effort to treat effectively under short-term confidentiality requested, please answer the following items separately as cited below. 16) The block diagram appears to suggest 2 different forms of FM couplers (one labeled “Sure Connect”, one labeled “FM Direct Adapter”). Please explain the differences between these various modes/configurations as necessary (i.e. are they leaky coax, what type of coupling is utilized, is the signal attenuated, length of cable, etc.). Please ensure this includes a description of operation/function of each. Answer – ‘Sure Connect’ is the marketing name for what we have previously been calling the FM Coupler. It couples the FM signal to the car’s FM antenna by virtue of it’s proximity. The ‘FM Direct’ adapter is inserted between the car’s FM antenna and the head unit. When an FM signal is present from the XM unit, the switch disables the car FM antenna, and connects the FM signal directly to the back of the car head unit. When neither the ‘Sure Connect’ or the ‘FM Direct’ devices are present, the signal is still present on the cable, but is attenuated by the cable shielding, such that it is not a practical method for connection of the FM signal to the car radio. As mentioned above, all three configurations were tested and found to be compliant. The XM Sure Connect accessory consists of a 2ft section of RF coaxial cable, followed by the FM/RF splitter module. The splitter module consists of both an RF jack which is used for the XM receiving antenna, and an 18 foot section of cable used for the FM coupling mechanism. There is 3dB of FM attenuation built into the splitter module. The FM direct adapter consists of a 6 foot section of RF coaxial cable, followed by the FM/RF switching module. The switching module consists of an RF jack which is used for the XM receiving antenna, and two 3 foot sections of cable used for the vehicle’s FM antenna and FM radio connections. There is 12dB of FM attenuation built into the switching module. 17) Please provide a technical description of operation/function of the FM coupler. Please upload this information as a separate exhibit (operational description) to ensure proper treatment of confidentiality. Answer - The FM Coupler works simply by placing the FM signal in close proximity to the car’s FM antenna by “clipping” the Sure-Connect accessory to the vehicle’s FM antenna. Due to the proximity of the coupler to the car’s FM antenna, it is considered to be in the very near field. Also, due to the low power level of the signal, and to the physical properties of the RF cable and the FM coupler, the signal is too weak to be usable via traditional radiated methods. Under these conditions, the signal is said to be ‘coupled’ to the antenna. 18) Please provide an appropriate installation manual for the coupler and/or direct configurations if this exists. Answer - The appropriate manuals have been uploaded. 19) Regarding the FM coupler, please explain what happens if the XM antenna is directly connected to the docking port and therefore bypasses the coupling module. Would this yield a leaky coax connection? Is it possible to bypass the coupling module this way?

Answer - When neither the ‘Sure Connect’ or the ‘FM Direct’ devices are present, but the RF antenna is connected, then the FM signal is still present on the RF antenna cable if the audio port is not populated. However, the signal is attenuated by the cable shielding, such that it is not a practical method for connection of the FM signal to the car radio. As mentioned above, this method was tested and found to be compliant.


Document Created: 2006-10-05 12:35:47
Document Modified: 2006-10-05 12:35:47
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