TMAA04-06 Cross-band Linking, GPS and External Interface Cable
3
© Tait International Limited February 2021
Priority scanning also affects the transmit timer during cross-band repeater transmissions. If
a non-priority channel in the group is captured, the radio will re-transmit that activity and the
transmit timer will begin counting down. However, each time the radio samples the priority
channel or channels, there is a brief break in reception which will cause the transmit timer to
restart.
Squelch override is not compatible with cross-band repeater operation. Avoid programming
this feature to a function key, and consider removing the menu option.
Transmit Inhibit
If both radios are receiving activity when cross-band repeater mode is activated, the radio
system can rapidly cycle between transmit and receive. Set Tx Inhibit to Busy to prevent this
from happening by not allowing the radio system to transmit when there is another busy
signal. Alternatively, set different debounce times for each radio, which will separate each
radio’s entry into cross-band repeater mode.
If the cross-band repeater is programmed to only re-transmit valid signals, and one radio is
receiving an invalid signal (such as invalid CTCSS), the mute will stay closed and no re-
transmission will occur. However, if the other radio then receives a valid signal, the radio will
attempt to re-broadcast this over the other signal. Set Tx Inhibit to Busy or Mute to prevent
this re-transmission occurring.
System Timing
For the cross-band repeater to operate correctly with other base stations or repeaters, system
timing must be taken into account. If using subaudible signalling and the transmitter requires
a “tail”, then this can be configured according to Table 4. During the lead-out delay period,
no signalling, such as CTCSS or DCS, is present.
Operational Testing
1. Enable cross-band repeater mode.
2. On the receiving radio, inject an on-channel RF signal at a level of - 70 dBm, modu-
lated to ±3 kHz deviation (wide bandwidth channel) or ±1.5 kHz (narrow bandwidth
channel), at 1 kHz AF.
3. On the transmitting radio, the resulting deviation should be:
■
± 3 kHz (with a tolerance of ± 200 Hz) on a 25 kHz wide bandwidth channel.
■
± 1.5 kHz (with a tolerance of ± 200 Hz) on a 12.5 kHz narrow bandwidth channel.
Table 4 Transmit tail in the Basic Settings form, Subaudible Signalling tab
Field
Setting
CTCSS Settings
Lead-Out Delay
any duration, up to 1000ms
DCS Settings
Lead-Out Delay
any duration, up to 1000ms
