User Manual

Installation and Operator Handbook Programming and Configuration
AMX-MA-00657 Issue: 1.02 (USA) Page 14
Link Radio cannot be selected when Enable Front
Panel PTT is enabled and vice-versa.
Half Duplex: When half-duplex mode is selected, the receiver is disabled when transmitting and
vice-versa. Half-duplex operation is only available in base-station mode.
Receive/Transmit Configuration
Freq (MHz): Enter the receive and transmit frequency for the selected channel. Note that the VHF
radio frequencies can be set to 1Hz precision. However for the UHF radio, entered frequencies are
internally rounded to a multiple of 5.0 kHz or 6.25 kHz (whichever is nearer) regardless of what is
displayed or entered in the frequency dialog.
When the DMR is operated in full duplex (simultaneous reception and transmission) isolation is
required between the receive and transmit signals to ensure that the receiver is not de-sensed by the
transmitter. The isolation is generally provided by a separate antenna or external RF combining
network. Table 5-2 and Table 5-3 show the minimum and recommended isolation levels for VHF
and UHF-Lo respectively.
Table 5-2 VHF Receive/Transmit Spacing
Receive/Transmit Spacing Minimum
Isolation
Recommended Isolation
<600 kHz - Not recommended
600 kHz to 1 MHz 85 dB >100 dB
1 MHz to 2.5 MHz 70 dB >80 dB
>2.5 MHz 60 dB 80 dB
Table 5-3 UHF-Lo Receive/Transmit Spacing
Receive/Transmit Spacing Minimum
Isolation
Recommended Isolation
<600 kHz - Not recommended
600 kHz to 1 MHz TBA TBA
1 MHz to 2.5 MHz TBA TBA
>2.5 MHz TBA TBA
Due to harmonics of internal clocks and oscillators degradation of receiver sensitivity may be
experienced on the following specific frequencies, and these frequencies should therefore be
avoided:
140.000000 MHz, 150.000000 MHz, 157.287500 MHz, 160.000000 MHz and 170.000000 MHz.
NAC (Network Access Code). For Project 25 / Autosense operation select the NAC as required,
using hexadecimal (Hex) notation. Receive and transmit NAC may be set independently, or the
transmit NAC may be set to be the same as the received NAC (‘Same as Rx’). If analog channel
mode is selected then these boxes will be disabled. Click on the Up/Down Arrows to
increase/decrease the current NAC value.