Technical Specs

Located on the borders of Chigwell in Hainault, GB7CH is A new multimode digital repeater for South Essex & East London

Picking up the aerial for the repeater at the Dunstable Downs Rally back in 2017. I had plans even back then!

On air from 10th December 2020 the repeater, formerly installed at the Kelvedon Hatch Secret Nuclear Bunker, GB7KH, has been repurposed to provide digital communications using the top three most popular modes. DMR, Yaesu System Fusion and D-Star.

Location: JO01ao

Repeater Specifications:

TX frequency: 439.6125 MHz
RX frequency: 430.6125 MHz
Colour Code: 3
TX Power (PERP): 7 dBW

DMR
Network: Brandmeister
Repeater ID: 234112
Slot 1: Dynamic
Slot 2: Static
TG 23511 (LEFARS)
TG 235 (UK Call)
TG 2350 (UK Chat)
TG 2351 (UK Chat)
TG 2351 (UK Chat)

Yaesu Fusion
Network: FCS
Default Group: FCS00291 – CQ-UK-WiresX

D-Star
Default Reflector: REF001 C

The Repeater Aerial is the 4 stack array on the top of the mast. It has great take-off to the South and Wast and limited take off North and reaches out to about the M25 to the east.

The repeater is a homebrew affair originally built by George Smart M1GEO and installed as GB7KH at the Kelvedon Hatch Secret Nuclear Bunker.

It consists of two Motorola GM340 Transceivers being fed by a Zumspot Modem on an Arduino, controlled by Pi-Star on a Raspberry Pi. A ProComm Duplexer provide filtering to enable the single dipole array to be used for full duplex transmit & receive.

It is planned to replace the Arduino / Zumspot with an MMDVM Hat for the Pi which should cut down the switching time of the repeater.

Want to see what going on? well here is the: Dashboard Link

V1.1 Dec 2020