GB7CQ – 70cm Digital Repeater Worthing


70cm Digital Repeater Worthing


Technical Information.

Licensed: 12 October 2020

Operational from: 16 October 2020

TX and RX: Motorola GM360 radio

UHF Duplexer: Procomm

Logic: Raspberry Pi and STM32DVM modem.

Antenna: Sirio GP365-470C tuned for the 70cm band.

Feeder: RG214

Power output: 6.5 dBW

Repeater keeper: G4WTV

Output frequency: 439.6125 MHz RX Frequency: 430.6125 MHz

Hardware donations.

The Motorola GM360 radio system donated by Andy G3UEQ & Roy G4WTV. Raspberry Pi and STM32DVM modem donated by G4KLX. Procomm UHF Duplexer donated by G4WTV. Antenna and other ancillaries from generous donations by local Amateurs.

To show your appreciation, it would be nice to contribute something to the setting up and running of the repeater. Use the button below to contribute via PayPal…

Thank you! Your contribution is much appreciated!

Activity on GB7CQ.

See what’s happening on the repeater. Link to GB7CQ dashboard:


GB7CQ: Predicted coverage map.

After the demise of our local 70cm DSTAR repeater (GB7JH) some time ago, we now have a new repeater up and running. This has been welcomed by local radio amateurs as the under used DSTAR mode has been brought back to life. The predicted coverage map for GB7CQ is shown below. Signal reports received so far have been most favourable, which is encouraging considering the height of the antenna is only 10 metres above ground.

GB7CQ predicted coverage map

What can you hear and connect to?

By popular demand DMR has been enabled on the repeater. DMR has the ability to have two simultaneous radio conversations on the repeater and these are known as Slot 1 and Slot 2. By default during the day and evening from 08:00 to 23:00, it’s connected to HubNet (TG23526) the all mode UK network on Slot 2. DMR Slot 1 is reserved for Local use on TG9. Overnight all DMR TalkGroups and D-Star reflectors are disconnected. Please feel free to connect to whatever you like at any time with DMR, D-Star or Yaesu Fusion. Please note that the repeater is not capable of simultaneous transmissions with two different modes, it’s one or the other. If the repeater seems to be busy but you’re not hearing anything, it’s because another mode is in use, so wait for a moment to use your mode of choice.

If you have difficulty in programming a radio for use on the repeater, please feel free to contact G4WTV who will be happy to help out.

Some info about the new logic.

The new repeater logic is based on a Raspberry Pi in order to make it future proof. The Pi has a STM32 modem fitted from which is a Multi-Mode Digital Voice Modem that gives new life to repeaters by allowing them to become internet compatible and many other possible enhancements. The STM32 has an on-board microcomputer, so there is no need for a separate Arduino or another processor board as all the linking is carried out in conjunction with the Raspberry Pi which runs Pi-Star, a software development by Andy – MW0MWZ, Jonathan – G4KLX, Hans – DL5DI and Kim DJ5VH. The whole new logic was donated by Jonathan – G4KLX who resides here in Worthing and is of worldwide fame for MMDVM development.

Logic internals

Yaesu System Fusion.

System Fusion is Yaesu’s implementation of Digital Amateur Radio, utilizing C4FM 4-level FSK Technology to transmit digital voice over Amateur radio. WIRES (Wide-coverage Internet Repeater Enhancement System) is an internet communication system which expands the range of amateur radio communication. For WIRES-X, GB7CQ is connected to the Internet and is used as the access point which connects the wireless communication to the internet. The introduction of C4FM / FDMA technology is the beginning of a new digital communication system in the Amateur Radio world. By default, GB7CQ is connected to YSF27793 the CQ-UK YSF reflector, but feel free to connect to your reflector of choice.

Please note that both DSTAR and YSF cannot be used at the same time, if the repeater is busy but you cannot hear anything, it’s probably because a different mode is in use. There is a network hangtime of 10 seconds at the end of the last transmission before either mode can be used.

Photos below…

Bench test, repeater logic and dashboard.

Photos below…

The repeater installed in the cabinet.

Photos below…

Logic internals. The Spectrum analyser plot of the high pass filter.  The Spectrum analyser plot of the low pass filter


Photo below…

The Procomm duplexer under test.The Procomm duplexer under test

The antenna.

Sirio GP365-470C tuned for the 70cm band.

GB7CQ antenna. Sirio GP365-470C tuned for the 70cm band.

Basic information about DSTAR repeaters.

Start your reading here –