What do all the connections on a SLR8000 repeater do?
The Motorola SLR8000 is a high-performance 100W repeater designed to provide reliable two-way radio communication coverage for large-scale and mission-critical applications. It supports both analogue and digital DMR operation. It has some interesting features such as; built-in wireline; local digital audio; an optional built-in preselector and antenna relay.
On the back are a number of connectors, for most of them it's quite clear what they do but for some of them it's not always very clear.
Mains Inlet
This is a standard IEC 60320 C14 socket (without the notch) that is used on computers. The SLR8000 is however supplied with a line cord as a standard accessory.
DC Inlet
This is a DC input from a battery backup system or inverter. It cannot be used to charge batteries, for that you will need an external charging system.
To connect the repeater to a DC supply, you will need cable PMKN4297A. If you like to roll your own, you'll need one Molex 42816-0212 plug; two 42815-0011 pins; a 30A 30V fuse; matching fuse holder; a ferrite ring that fits; suitable 6mm² red and 6mm² stranded insulated black wires.
Wireline Interface
Only the leftmost RJ45 socket works. This socket is to be used for Tone Remote or DC Control. The pinouts are as follows:
| Pin | Function | Comment |
|---|---|---|
| 1 | Line 2 + | 2-wire input/output 4-Wire output 600Ω |
| 2 | Line 2 - | 2-wire input/output 4-Wire output 600Ω |
| 3 | Aux 1 In + | Opto-coupled DC loop |
| 4 | Line 1 - | 4-Wire input 600Ω |
| 5 | Line 1 + | 4-Wire input 600Ω |
| 6 | Aux 1 In - | Opto-coupled DC loop |
| 7 | Aux Out Relay 1 | Form A contact. Part of DC Remote Control. |
| 8 | Aux Out Relay | Form A contact. Part of DC Remote Control. |
Most of the settings related to this are in the CPS. On the wireline board itself, there are some jumpers that are not needed for wireline operation but are needed for DC Remote or E&M operation - if you need either of these, I suggest reading the installation manual MN002299A01.
Receiver Input
If no antenna relay is used, the cable from the duplexer or multicoupler will connect here.
GNSS
This is currently not used.
Wi-Fi
This is currently not used.
Circulator Temperature Sense
A number of external circulator trays are available for this repeater. The required cable comes with the tray. The purpose of this sense line is to measure the temperature of the dummy load used on the circulator. If this dummy load gets hot, it means there is a SWR mismatch or RF is escaping from another repeater and making its way to the circulator. a hot dummy load in this case generates an alarm.
Transmitter Output
If no antenna relay is used, the cable from the duplexer or combiner will connect here.
Ground Terminal
This allows you to connect the repeater chassis to the cabinet or rack ground using a 6mm ring lug. The mains ground cannot be used or relied on. Apart from R56 non-conformant, in many countries it is not allowed to use the mains for anything other than sensing ground fault conditions.
Antenna Relay
An antenna relay allows the repeater to be used as an analogue transceiver connected to a dispatch console via E&M; Tone or DC Remote control.
An antenna relay cannot be used for ERDM (SFR) or repeater-mode operation!
If an antenna relay is used, the antenna will be connected to the antenna socket.
Preselector
Although outside the scope of this post, the SLR8000 is available with a receive preselector. This improves the receive spurious rejection by around 15dB but will reduce the sensitivity by around 1dB. This component needs to be tuned before use.
Auxiliary Connector
This connector is more interesting and provides a number of inputs and outputs from the repeater. It's a standard Subminiature DB25 connector - you'll need a male plug.
On this connector is an audio input and output as well as a number of CPS (or RM) configurable General Purpose Input Output lines. There is also a 12V source which will allow you to power (low power) things like repeater controllers. Things like trunking controllers require more power and must use their own power source.
| Pin | Function | Comment |
|---|---|---|
| 1 | TX Audio | 80mV RMS for 60% deviation. 600Ω |
| 2 | GPIO1 | CPS configurable input or output. See below. |
| 3 | Not Used. | - |
| 4 | GPIO2. | CPS configurable input or output. See below. |
| 5 | GPIO10 | CPS configurable input or output. See below. |
| 6 | GPIO9 | CPS configurable input or output. See below. |
| 7 | RX Audio. | 300mV RMS (at 50kΩ) with a 1kΩ nominal impedance. |
| 8 | GPIO6. | CPS configurable input or output. See below. |
| 9 | Ground. | Does what it says on the box. |
| 10 | GPIO7 | Can also be used for analogue RSSI measurements. See below. |
| 11 | GPIO11. | CPS configurable input or output. See below. |
| 12 | GPIO12 | CPS configurable input or output. See below. |
| 13 | TX Data. | Can be used to send data or CTCSS/DCS when operating in analogue mode. |
| 14 | Not Used. | - |
| 15 | GPIO3 | CPS configurable input or output. See below. |
| 16 | Ground. | Like it says. |
| 17 | Ground. | "" |
| 18 | Ground. | "" |
| 19 | Ground. | "" |
| 20 | Fused B+. | Provides a 12V source at maximum 1A. |
| 21 | GPIO8 | CPS configurable input or output. See below. |
| 22 | TX Audio. | 80mV RMS for 60% FM deviation. 600Ω impedance. |
| 23 | GPIO4 | CPS configurable input or output. See below. |
| 24 | GPIO5 | CPS configurable input or output. See below. |
| 25 | Not Used. | - |
If you are going to be using any of the above GPIOs and any of these will exit the equipment rack or cabinet, you need to include some form of galvanic isolation such as an opto-coupler. Not implementing isolation can result in (expensive) damage to the repeater and/or external equipment.
Each of the GPIO can be programmed to one of the following. When configured as an output, normal TTL levels will be used (i.e. <0,5V low; 5V high). In this case, the output comes from the collector of a transistor with an internal 4k7 pull-up resistor. When configured as an input TTL levels also apply, except that anything below 0,8V is regarded as low and anything above 3V as high - with 5V maximum.
| Selection. | Input/Output. | What this does. |
|---|---|---|
| AC Power Failure | Input | Overrides the alarm generated by a mains fail. |
| Antenna Relay | Output | Used to trigger the relay whenever PTT is pressed on the console. Analogue base station mode only. |
| CSQ Detect | Output | Will change state whenever carrier is detected. Analogue mode only. |
| Channel Select 1-6 | Input | Will cause the repeater to go to a selected channel by inputting a BCD number using these pins. |
| Disable. | Input | Disables the repeater. The repeater will do a reset whenever this chnages state. |
| External PTT | Input | This causes the repeater to transmit. Analogue mode only. |
| FCC Type 2 Monitor | 2 | 3 |
| Football Knockdown | Input | 3 |
| Major Alarm | Output | Changes state if a minor alarm occurs. Major alarm also locks the repeater. |
| Minor Alarm | Output | Changes state if a minor alarm occurs. If Backup Repeater Connected is ticked this will be summed with Major Alarm. |
| Monitor | Input | Overrides the squelch condition. Analogue only. |
| PL/Talkgroup Detect | Output | Changes state if CTCSS/DCS is detected - if in analogue mode. In digital mode will change state if a talkgroup is busy. |
| Repeater Knockdown | Input | Disables repeater operation but allows an external controller to have control. |
| Reset | Input | Makes the repeater do a reboot. |
| TX PL Inhibit | Input | When asserted will strip CTCSS/DCS from transmissions. Analogue only. |
| TX Power Level High | Input | Will make the repeater use high power, no matter what the codeplug says. |
| Unassigned | Neither | Set any unused GPIOs to this. |
| Wireline External COR | Output | - |
| Wireline External PTT | Input | This will make the repeater transmit and send any audio present on the wireline. |
| Wireline Mute Input | Input | - |
| Wireline Mute Output | Output | - |
A word on Active Level and Debounce
Debounce is only applicable when the GPIO is set up as an input. The duration can also be be defined. Debounce protects the repeater and system from false triggers caused by defective switch or relay contacts.
Active Level determines whether the GPIO goes high or low when the configured condition is met.
Ethernet
Ethernet 1 is standard 802.3 ethernet. Ethernet 2 is not available currently.
External Reference
This allows an external high stability oscillator to be connected to the repeater. The internal oscillator can provide 0,5ppm stability provided the temperature remains between -30°C and +60°C.
USB
This connector is not currently used.
The other is the USB programming connector. Here you can use the DN9957A cable or a spare printer (USB A-B) cable.
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