GPS Antennas for Sync 3 Retrofits
This article is meant to help people with the proper choice of a GPS antenna for retrofitting a Sync 3 APIM to vehicles not equipped with Sync 3 OEM, such as Sync 1 or 2 platforms. This information does not pertain to Sync 4 OEM vehicles or the Sync 4 platform.
Overview
The Sync 3 platform works best with aftermarket antennas having the following specifications:
- Center Frequency: 1575.42 ±1MHz.
- Impedance: 50 Ohms.
- Gain: 28 ±2dB.
- Supply Voltage: +2.2 - 5V DC.
- Current Consumption: 5-15mA.
- Double shielded coaxial cable.
- Polycarbonate Radome housing with steel base plate.
There are a few items to note in the above specifications which are often overlooked when selecting a GPS antenna for this application, which specifically are the antenna gain, supply voltage, and current consumption of the antenna LNA. This is especially important for the installation of the antenna in a Sync 3 application, as the antenna gain should be set correctly to avoid GPS receiver saturation or loss of signal.
The antenna is specified as requiring a supply voltage of +2.2 to +5 VDC. This controls the maximum gain of the antenna. Too much gain results in excessive received signal amplification, which will desensitize the GPS receiver input. Too little gain will result in a weak signal to the GPS receiver input, causing a loss of signal condition. Either condition can cause issues with the proper functioning of the navigation subsystem in the Sync 3 APIM. (This is a separate part of the APIM which is unrelated to the Sync 3 software or firmware.) To minimize either condition above, there is a setting in the Sync 3 software asbuilt which should be adjusted to account for the placement of the antenna in or on the vehicle. The setting is designed to accommodate the various mounting points and signal conditions expected. This setting is located at 7D0-03-01 x*xx-xxxx-xx.
GPS Mount Type (GPSMT)
7D0-03-01 x*xx-xxxx-xx
0 = Roof Mount
1 = Instrument Panel (IP) Mount (Non Heated Windscreen)
2 = Instrument Panel (IP) Mount (Heated Windscreen)
3 = Windshield Mount (Non-Heated Windscreen)
4 = Windshield Mount (Heated Windscreen)
5-F=Reserved
Antennas and Antenna Placement
There are many aftermarket GPS antennas available on the market, but this article is not meant to endorse any specific manufacturer or seller, but only to give the reader a frame of reference on what to purchase for their Sync 3 upgrade project.
Virtually all the aftermarket GPS antennas manufactured for this application are magnetic mount bases with 3 meters of coaxial cable. This obviously gives the most versatility in choosing a mounting location for the antenna. One thing to remember here is to never shorten or lengthen the antenna cable. This will result in shifting the center frequency of the antenna and affect the gain. Although it may still work with no issues in one location with strong satellite signal, it will likely leave you without sufficient signal in remote locations, depending on the satellite coverage at the time.
The mounting location of the antenna in or on the vehicle must be a location which the antenna can see “clear sky”, meaning ideally there are no obstructions. This is often not possible, but the alternative is to mount the antenna where there is no metal or conducting obstructions. This includes metal body parts and wiring bundles above the antenna. Interior soft parts, like the top of the instrument panel, are mostly “invisible” to the GPS antenna, meaning they do not block or minimally block the GPS satellite signal. Obviously, the best mounting position for this application is mounting the antenna on the roof, but this location can have its own issues with mounting, wiring, weatherproofing, etc. Mounting the antenna inside the upper portion of the dash works well in most instances.
Below are two aftermarket antennas that seem to work well for this application. Again, these are just examples.
GPS Antenna for Mercedes E-Class W211/Aps 50 Clk W209 Fakra Female 3M GP-05-3M
GPS Antenna For Mercedes E-Class W211/Aps 50 Clk W209 Fakra Female 3M GP-05-3M | eBay
GPS Antenna FAKRA C Blue 1575MHz Magnet Navigation for Ford SYNC Audi VW
GPS Antenna FAKRA C Blue 1575MHz Magnet Navigation For Ford SYNC Audi VW | eBay
General Aftermarket Antenna Specifications for Sync 3 Retrofits
Antenna
Center Frequency: 1575.42 ±1MHz
Band Width: CF ±5MHz
Polarization: RHCP
Gain: 2 dBic Zenith
V.S.W.R: ＜1.5
Impedance: 50Ω
Axial Ratio: 3dB
Double shielded coaxial cable.
Made of strong polycarbonate Radome housing with die-cast steel base plate.
LNA
Gain: 28 ±2dB
Noise Figure: ＜1.5
Filter Insertion Loss: ＜3dB
Ex-band Attenuation: 12dB@CF+50MHz/16dB@CF-50MHz
Supply Voltage: 2.2-5V DC
Current Consumption: 5-15mA
V.S.W.R: ＜2.0
Mechanical
Cable: RG174
Connector: Fakra C Signal Blue
Radome Material: ABS
Mounting Method: Magnet
Environmental
Operating Temperature: -40℃~+85℃
Relative Humidity: Up to 95%
Ingress Protection: IP67
Vibration: 10 to 55Hz with 1.5mm amplitude 2 hours
Environmentally Friendly: ROHS Compliant