L-Tronics  makes several receiver models that generate an alert when an ELT signal is heard.  They all listen continuously on either 121.5 or 121.5 and 243 MHz  and all use a frequency comparison squelch system that constantly adjusts the receiver for maximum usable sensitivity. This allows the monitor to separate a barely audible ELT/EPIRB signal from background noise produced by storms or nearby machinery or appliances. It will respond to an ELT that is damaged or has no modulation, as well as a carrier signal produced by a stuck microphone. An adjustable integrating timer in the unit, usually set to 10 minutes, prevents alarm trips on voice conversations or ELT tests.

The base station units are intended for fixed locations such as a home, office airport or harbor where people are present.  Once the monitor detects a signal, it can be used to locate the source in the same manner as the standard LH Series DF.  The mountain top units are built for installation at radio repeater sites and generate an alert through the radio system.  The "D" models have an internal DTMF (Touch-Tone) controller while the less expensive "E" models depend on the radio system controller.

Monitors can greatly assist rapid response to both accidents and false alarms.  The Santa Barbara Monitor System is a summary of over 9 years of operation of a group of these receivers.

Base Station Monitor / Direction Finder

This monitor is usually left running in its desk stand and connected to AC power.   When the alarm activates, the speaker comes on. It can also trigger an optional auto-dialer for remote reporting of the alarm by telephone. A mute button disables the speaker and causes the dial light to flash brightly as a reminder that the signal is still being received. The unit resets automatically when the signal which tripped it is gone.

The LH-16AM is also a complete LH-16 VHF/UHF direction finder, identical to the LH-16. All technical specifications are identical to the LH-16. The LH-16AM can accommodate up to 3 VHF and 2 UHF frequencies and is supplied with 121.5, 121.6, 121.775, 243 and 243.2  MHz. Also included with the LH-16AM system are portable antennas for each band, a long and short mast, outside antenna with 50 feet of coax, metal desk stand, AC power adapter, operating & maintenance manual, and batteries. For fixed site DF our LWA-16 Weatherproof antenna may be used on a tower with a rotator.  The LH-16AM can also be used in a vehicle or aircraft.