THE LINK-11 MONITORING SYSTEM (LMS-11)

THE LINK-11 MONITORING SYSTEM (LMS-11)— The LMS-11 provides the operator and technician with a means of monitoring the integrity of the Link-11 net. With the LMS-11, the technician has a real-time visual display of the link while it is operating. The LMS-11 consists of the following three groups of equipment: the data processing group, the control/display group, and an accessory group. The data processing group contains the central processor and the interfaces required to process the link audio. It also contains a dual 3.5-inch floppy disk drive and the power control unit. The control/display group consists of a color graphics monitor and a keyboard. The keyboard provides the operator interface with the LM-11. The functional keys on the keyboard are color-coded for ease of operation. The accessory group consists of the color graphics printer and the spare parts and supplies for the LMS-11. LMS-11 OPERATION AND DISPLAYS— The LMS-11 has five on-line modes of operation. Each mode has a unique display screen and allows the technician to evaluate various parts of the link audio signal and the link digital data. The five modes are as follows: LINK MONITOR, NET DISPLAY, PU, SPECTRUM, and CARRIER SUPPRESSION. LINK MONITOR MODE— The link monitor mode provides the technician with a real-time display of link activity. This allows the technician to monitor and detect link problems as they occur. NET DISPLAY— The net display contains the following two distinct modes of operation: the NET SUMMARY and a PU HISTORY. The Net Summary mode presents a summary of quantitative information about the performance of up to a maximum of 21 PUs in the net. The PU History mode displays the same quantitative data for a single PU. This data is updated each time the selected PU transmits. The most recent 21 transmissions of the specified PU are displayed in the PU History mode. PU DISPLAY— The PU display presents detailed information about the audio signal received from a specified PU. The information is presented in two bar graphs and shows the relative power and the phase error of the received signal. SPECTRUM DISPLAY— The spectrum display shows the relative power level of the Link-11 tones and the noise tones that are the odd harmonics of 55 Hertz. The 605-Hz tone is used as a reference and is set to 0 dB. The relative power of the data and noise tones is displayed with respect to this level. In this mode, the effects of noise can be easily viewed. CARRIER SUPPRESSION— The carrier suppression can only be measured while in Net Sync. The LMS-11 measures the power of the carrier frequency and compares it to the power of the 605-Hz tone. The carrier suppression can be measured accurately when the radio is off-tuned by – 500 Hz for the USB and +500 Hz for the LSB. EVALUATING THE LINK-11 NET— The LMS-11 can be a very useful tool in evaluating Link-11 net operations. The best way to become proficient on reading the various screens of the LMS-11 is through practice. 3-20