Introduction

The following describes NVFMA's 70-centemeter FM repeater, the "447.025 machine".

Call Sign

The 447.025 machine is operated with NVFMA's club call sign NV4FM. The call sign is automatically transmitted by Morse code at least every 10 minutes when the repeater is transmitting.

Location

The 447.025 machine and its antenna are located in Tysons Corner in Northern Virginia.

Transmit and Receive Frequencies

The 447.025 machine's transceiver transmits on a frequency of 447.025 MHz using frequency modulation. It has a standard -5.0 MHz receiver offset. This means that the receiver frequency is 442.025 MHz.

Private Line (PL) Tone Sensing

The 447.025 machine's receiver responds to a PL tone of 77.0 Hz, so all signals received without this tone are filtered out. A 77.0 Hz PL tone is added to the transmitted signal to support the Continuous Tone Coded Squelch System (CTCSS), if desired.

Operational Status

The 447.025 machine is fully operational.

Antenna

The following image shows the antennas on top of the building in Tysons Corner that hosts the 447.025 machine.

Timer

The 447.025 machine includes a timer that automatically terminates repeater transmissions after any continuous three-minute period of operation. This feature provides the opportunity for the repeater's transmitter to cool down, but it also encourages users to limit the duration of their transmissions to no more than three minutes without a break. The timer is reset when the received signal drops. A station transmitting to the repeater may not realize that their signal is no longer being repeated through when they transmit too long. Operator discipline is necessary.