Date of application: 03/06/2021
Project description: GB3ZZ has two inputs on 1249 & 437MHz. Each input has a primary receiver running 4ms/s on 1249MHz and 2ms/s on 437MHz. These receivers are quite elderly Comag satellite receivers which have proven to be remarkably reliable over many years use.
In recent years, we have attempted to provide a secondary receiver for each input running a lower symbol rate of 1ms/s. This has been attempted using a variety of commercial satellite receivers operating at their minimum symbol rate setting. We have used modern receivers which in theory can automatically switch modes (DVB-S/S2) and codecs. However, these have never proved entirely satisfactory and are prone to becoming unresponsive when subject to repeated mode and codec changes.
With the development of the BATC Ryde and its revolutionary symbol rate scanning function, we saw an opportunity to provide a comprehensive low symbol rate input on both 1249 & 437MHz. The proposal is that on 1249MHz, the receiver will scan 333ks/s, 1 & 2ms/s. On 437MHz, it will scan 333ks/s & 1ms/s.
Each receiver will be powered by a timer/shut down box. The receivers have been provided with the hardware shut down facility. The timer box contains two timers, the first of which shuts down the Raspberry Pi and the second cycles the power to reboot it. We have used this approach for the Portsdown repeater streamer and it has proved highly effective in dealing with the quite rare occasions when the Raspberry Pi crashes.
Benefits to ATV community:
This application is retrospective and it is possible to report that these receivers were made operational in early December 2020. They have been remarkably successful and have operated without intervention for three months. The improvement in sensitivity using the 333ks/s inputs has been beyond all expectations. Stations that previously could not access the repeater are now able to get in and even more distant stations such as G4UVZ in Taunton can access on a few tens of milliwatts.
Total amount of funding requested: £257.78
Details of costs / items: This work has been costed as follows;
2no. Minitione PCB’s (BATC shop) @£4.50 £9.00
2no. Serit NIM tuner modules (BATC shop) @£25.50 £51.00
2no. MCP1826 voltage regulators (BATC shop) @£2.00 £4.00
2no. FTDI USB modules (BATC shop) @£26.50 £53.00
2no. Raspberry Pi model 4B+ (Pi hut) @£33.90 £67.80
2no. micro SD cards (7 day shop) @£6.49 £12.98
Misc. parts for Minitioune boards (Digikey) £60.00