GOES DRGS Feed / LNA / Down Converter
The Stevens GOES DRGS Feed, LNA and Down Converter consists of the Feed, Low Noise Amplifier (LNA) and Down Converter that is mounted at the focal point of the parabolic dish antenna. It picks up the 1694.45 MHz signal broadcast from the GOES satellite and reflected from the parabolic dish antenna. The Low Noise Amplifier (LNA) circuit amplifies the signal to an acceptable level and then down converts it to a nominal 140 MHz IF. This IF signal then sent via a RG-8 coaxial cable to the indoor DRGS equipment collocated with the receiver site computer.
The integrated Feed-LNA-Block Down Converter operating temperature range meets the 0° to 50° C specifications and humidity of 0 to 90 %, non-condensed. The DC power requirements are +12 to +16 VDC at 0.6 Ampere at turn on; 0.3 Ampere after warm up. Any center frequency within the range of 1.2 GHz to 2.5 GHz may be specific and, therefore will be provided at the 1694.45 MHz as specified by CVC and for the GOES DCS.
The integrated Feed-LNA-Block Down Converter is protected against over voltage, electrical interruption, electrical discharges, transient via a strap to the aluminum dish that will be grounded to the earth ground.
The nominal satellite polarization is linear and can be manually adjusted. The integrated feed/electronic assembly is designed to mate with a parabolic of approximately 0.4 F/D to provide reception and block down conversion of signals within a total bandwidth of 1% of Fin. Linear, right, or left hand circular feed polarization may be specified.
The unit is weather tight; double O-ring sealed and powder-coated white. DC power is fed up the IF output cable. The entire assembly can be rotated within an outer mounting ring to allow adjustment for linear polarization.
The following table presents the technical specifications for the Feed:
Low Noise Amplifier and Bandpass Filter
The Low Noise Amplifier (LNA) is provided in an enclosure that provides environmental protection. This assembly is mounted at the focal point of the antenna
A bandpass filter is an extremely narrow filter centered around the signals received from the satellite and is physically located before the LNA but after the GOES signal feed. The purpose of the filter is to provide rejection from local interference signals in the vicinity of the receiving antenna. In some cities, the local microwave traffic and cellular telephones cause LNA saturation at the focal point of the antenna. This is very common on rooftop installations. The filter allows interference free (unless signals are directly in the GOES band) operation with a very small overall link penalty of less than 1 dB. The following are the LNA and Bandpass Filter specifications:
The down converter is used to provide the conversion of the 1694.45 MHz S-Band signals to much lower frequency signals of 140 MHz allowing for long cable runs to the receiver. Distances well over 200 meters in length (between down converter and the receiver located inside the building) have been installed in the past and are easily accommodated without signal or gain loss. The cable running between the down converter and the receiver consists of one RG-8 cable. The single cable handles both DC power and the return IF received signals. The following are the down converter specifications: