The total number of channels in G/A transceivers that may interfere with GPS is unpredictable (primarily because manufacturers use different intermediate frequencies) and much larger than thirteen, making it impractical to remove them from use in terminal area operations. It is concluded that discontinuing the use of up to 13 VHF communications channels for certain terminal area operations is not a viable solution to the VHF-GPS interference problem. Two units, one G/A class and one air carrier class, had case emissions which did not meet FCC specifications. All observed antenna port emissions were in conformance with applicable TSO and FCC emission specifications regarding out-of-band radiated power. However, a significant number were clearly at magnitudes that could cause interference to GPS receivers on the same aircraft. Based on signal strength measurements, not all of the emissions are equally likely to interfere with GPS reception. The case emissions were comparable to the levels measured in the G/A units. The antenna port emissions were at or near the minimum power level that can cause interference in an aircraft installation. Reset history tracking data quickly and easily. Store history of tracking data along with the real time data display. TRACKING Keeps track of travelled distance, average speed and top speed. The two remote-mounted air carrier class transceivers tested were found to emit only transmitter harmonics from the antenna port and case. GPS INDICATOR Show GPS accuracy indicator. Emissions in the L1 band were observed from one or more units from the antenna port for a total of 198 VHF frequencies, and from their cases for 32 VHF frequencies. In addition, spurious (non-harmonic frequency) emissions as well as local oscillator harmonics were found. The thirteen transmitter harmonics were found to be emitted from both the antenna port and the transceiver case. Test results show that there are many more than 13 VHF communications channels in G/A transceivers that can potentially interfere with GPS receivers. These tests were performed to address reported and potential problems involving VHF transceivers interfering with GPS receivers on-board aircraft, particularly in the G/A class. The goal was to measure all radio frequency (RF) emissions from the transceiver antenna port and its case that fall in the Global Positioning System (GPS) L1 band (1575.420+/-1.023 MHz). Laboratory tests were performed on ten different panel-mount type, General Aviation (G/A) class VHF communication transceivers, and two remote-mounted Air Carrier class VHF transceivers. VHF transceiver tests described in this report were performed at the Volpe National Transportation Systems Center under Federal Aviation Administration (FAA) sponsorship. Each media stream information is printed within a dedicated section (an array item) with the name "STREAM".VHF Transceiver Emissions in the GPS L1 Band -show_streams: This option shows information about each media stream contained in the input multimedia stream.All the container format information is printed within a section with the name "FORMAT". -show_format: This option shows information about the container format of the input multimedia stream.-print_format : Sets the output printing format to output in JSON, INI, XML, or CSV format.If any error occurs and no information can be extracted, the process won't fail but will return an empty JSON. -loglevel -8: Shows absolute nothing of the output of ffprobe.The command to extract the information of a media file using ffprobe in JSON format is the following one and each option is described as follows: In this article, I will show you a very basic command to extract information about the media files before processing them using FFPROBE (FFMPEG). This information could be handled by any programming language that is capable of parsing the JSON format. For example, it can be used to check the format of the container used by a multimedia stream and the format and type of each media stream contained in it. FFPROBE gathers information from multimedia streams and prints it in human- and machine-readable fashion and comes as well with FFMPEG. In case that you are working with FFMPEG through the command line and manipulating it with a programming language like Python, JavaScript, PHP, or any other language, you may obtain an extra conditional layer of information about the input files using FFPROBE before working on the files with FFMPEG. When working with FFMPEG from the command line, we have always dreamed of some kind of feature that would allow us to proceed with the execution of an instruction that only works if the given input fulfills some special characteristics like the number of streams, the codec, or other things.
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