GB3CT

Welcome to GB3CT a new multi-user repeater located at Caistor Top in the Lincolnshire Wolds with the site situated at 127 metres ASL. It has been built and is maintained by G7KPM and the Grimsby ATV group which also operates GB3GG in Grimsby, N.E. Lincolnshire.

GB3CT uses the new transmission standard for ATV repeaters of 1M/symbol 2/3FEC at 3404Mhz and is built using the BATC Portsdown software, Pi3, Lime SDR and a Stealth Microwave PA which was generously donated by the GB3KM group. The Portsdown system hardware has been funded by the BATC bursary and was one of the first projects approved for funding when the scheme was launched a couple of years ago. Since then, the BATC has generously funded the hardware cost of 2 Ryde receivers for a 70cm digital RX and 13cm hybrid receiver through it bursary scheme. The system is being constructed to operate the following:

TX - 3404Mhz DVB-S2 - 1M/symbol - 2/3 FEC

RX1 – 437Mhz digital

RX2 – 2435 - 2330Mhz analogue FM & digital

RX3 – 5775Mhz analogue

RX4 – 10.315 - 10.425 Ghz analogue

RX5 – Skype input # 1

RX6 – Skype input # 2

The repeater has a simple PIC based logic controller which was described in CQTV xxx and uses a pair of multi-screen processor units, a quad and 9 screen, both of which were obtained as CCTV surplus. The quad is used to display any combination of inputs 1 to 4 and the 9 screen to display either a single full screen of any of the inputs and a 9 screen cameo when inputs 5 and above are active together with any other active input. The logic controller operates the alarm inputs on the 9 screen cameo which is then displayed on the spot monitor output. It is envisaged that these will eventually be replaced by HDMI processors once an all digital design concept has been developed sometime in the future.

Block diagram of the current repeater