GB3PF Equipment

GB3PF Repeater

GB3PF is housed in a 1m tall 19" computer comms cabinet. In the top of the cabinet are cooling fans, they are temperature controlled and it's not expected they will ever run. On the top shelf is the repeater controller, this was custom made by M0NFI for GB3RF. The Icom IC-FR4100 repeater is on the lower shelf. To the right of the repeater you can see the N connectors of the Procom duplexor that sits vertically at the right hand side of the cabinet. In the bottom of the cabinet are the backup batteries for the repeater and controller.


GB3PF is an Icom IC-FR4100 commercial repeater. It is full duty cycle rated which means it can transmit continuously and it's large heatsink and fan keep it cool. This is an important requirement for a linked repeater. HUBNet is very active and the repeater can be transmitting for several hours continuously at busy times.

The repeater contains an automatic battery backup system.

Temperature sensors have been added to the PA and power supply units to allow the temperature to be remotely monitored. The sensors are connected to the 25 way D accessory connector on the repeater. This connector carries all the required signals to the repeater controller.




Gateway Controller

A Raspberry Pi 3 is used to control the gateway nodes and is using the hamvoip V1.5 image.

Remote control features on the Raspberry Pi's allows status checking and monitoring remotely. The radios temperature is monitored using the added internal temperature sensor. The cooling fan is controlled using a script to control a GPIO output on the RPi.

From left to right inside the controller, 12v to 5v PSU, Raspberry Pi 3b, interconnection/power/fuse board, 4 relay board for turning the repeater on/off and fan control, GSM switch to allow remote shutdown.



Radio Interface

The interface between the repeater and the Raspberry Pi controller is a modified CM108 chip based USB sound card. It is modified to provide the PTT switching of the radio and monitoring of the COS output from the radio. The COS signal tells the RPi a signal is being received by the radio with the correct CTCSS tone.




A Procom DFF 70/6 150 duplexer on loan from the North Western Repeater Group is used, many thanks to them for the use of it. This provides the required isolation between transmitter and receiver and to allow a single antenna to be used for transmitting and receiving with a 1.6MHz split at the same time. This duplexer was previously used on the original GB3PF repeater before it was closed down by the North Western Repeater Group.

A Procom MPX 70/6 is shown below with the Procom DFF 70/6 to show how large the DFF is compared with the commonly used wide split type duplexers found in many DMR repeaters.



GB3PF's antenna is a Diamond X50N mounted 10m above ground level. The antenna is mounted on top of the pole with the coax running down the centre of the pole instead of using the original mount with the coax outside the pole. This is a much neater installation and improves on the single bolt mount that the original mounting has that allows these antenna to wobble on top of the pole.  The antenna sits inside an 1 1/4" alluminium 16 guage pole. The pole has a short slit at the top to allow a 32mm exhaust clmap to securely hold the antenna in place. The 1 1/4" pole sits inside a 1 1/2" pole using a custom made sleeve and exhaust clamp to secure the two together.