Garmin GDL 69/69A Installation Manual

Also see for GDL 69: Pilot's guide addendum Pilot's guide addendum Activation Instructions Pilot's guide Activation Instructions

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Garmin GDL 69/69A Installation Manual Manual pdf 31 page image

Installation ProcedureGDL 69/69A Installation Manual Page 2-15190-00355-02 Revision ETable 2-7. XM Gain/Loss Component CalculationAntenna Gain (1) +Cable Loss (2) (3) -GDL 69/69A Gain/Loss (4)+6dB > x > -4dB +/-Total GainAntenna/Receiver = 20 dBNote:(1) Garmin GA 55, GA 55A, GA 57 XM antenna typical gain 25 dB. For antenna gain for otherantennas, see manufacturer’s specifications.(2) If 12-16ft of RG-400/U cable is used, a value of 4.5dB can be used. See Section 2.6.4.1 forexplanation of calculation.(3) If an antenna with increased gain is installed (antenna other than the Garmin antennas listed inTable 1-5), additional cable length may be required to be coiled to compensate for the requiredcable loss. Alternately, an external attenuator may be used to obtain the desired antenna cable loss.However, installation of the external attenuator is beyond the scope of this STC. Additionalmanufacturer’s data may be necessary and FAA approval may be required to cover the installationof an external attenuator.(4) The GDL 69/69A Gain/Loss component must be between +6dB and -4dB. If the GDL 69/69Again/loss component is outside this range, additional gain or loss must be added between theantenna and the GLD 69/69A RF input. The factory default setting for the internal GDL 69/69Acomponent is -0.5dB. The variable attenuation value required to attain the GDL 69/69A gain/losscomponent will be programmed into the configuration module during post installation checkout.See Section 2.6.4.2 for explanation of calculation.2.6.4.1 Determining Antenna Cable Loss ValueThe GDL 69/69A is factory preset with a default cable loss value of 4.5 dB, which is equivalent to 12 to16 feet of RG-400/U cable with two properly terminated TNC connectors. If the installed antenna cable iswithin this length, use this value in Table 2-7. If the cable is different from the default cable, use thefollowing formula to determine the cable loss value to use in Table 2-7.Loss in dB = (Length x Loss) + (0.5 x #Connectors)100Where:Length – Cable length in feetLoss – Specified cable loss per 100 feet at 2332-2345 MHzConnectors – Number of connectors on cableFor example:If an RG-400 coax cable is 10 feet long with 2 TNC connectors, the cable loss component isLoss = (10 x 26.1) + (0.5 x 2) = 3.61 dB100