GB3PV Digital RF Switching Logic
I've was asked to help with some logic on GB3PV, a 23cm ATV (amateur television) repeater in Cambridge. GB3PV is being upgraded to support digital alongside analogue for which some logic is required to switch between the analogue and digital transmitters, actually done by an RF relay. The best solution is going to be a PIC based one due to flexibility and size. The requirement for the logic includes 5 input signals with the switching being done based on the current active ones, or last known state. The inputs are Beacon_Active, ATV_RX, DATV_RX, ATV_RX_DATV_TX and DX_Mode_Enable. The basic logic outline was every second Beacon_Active would be digital and required the RF relay to be energised. ATV_RX would overwrite everything and move the relay to analog. While there was an ATV_RX the user can activate DATV by DTMF (ATV_RX_DATV_TX) or DX mode (DX_Mode_Enable) which switched the repeater 'off' for 10 mins or until ATV_RX or DATV_RX is seen which allows users to work weak distant stations on the same frequency if there is a 'lift'. It turned out to be very simple and only required 124 lines of code. The good thing about this project is I introduced Brian G6HFS to PICAXE and after I gave him the initial code and PCB he has done some enhancements and 'bug' fixes, his first venture into PICs!
The code is not really relevant to anything other than this project so I've not published it. However if you think you could use it and would like a copy please email me - gnesbitt <at> orange <dot> net.
Downloads
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File Size: | 412 kb |
File Type: | bmp |