- Joined
- Jul 4, 2009
- Messages
- 16,235
- Helped
- 5,140
- Reputation
- 10,309
- Reaction score
- 5,120
- Trophy points
- 1,393
- Location
- Aberdyfi, West Wales, UK
- Activity points
- 137,398
I had a thought - that is usually dangerous so read on with caution:
I have to design a low cost radio time code receiver for use in the UK. It isn't a "wall clock", it has to format the date and time so it fits in a packetized data stream but I can do that easily. There are two radio references I can use, an ASK signal on 60KHz (similar to DCF77) or a 25Hz phase encoded time signal embedded in the UK's "Radio 4" service on 198 KHz. I am leaning toward using 198KHz because the coverage is better and the signal is stronger in most places but the data is harder to decode. Only a few of the modules will be built so it isn't worth designing a custom device but the cost/component count has to be as small as possible.
The idea is to use a PIC with quadrature encoder inputs, one fed from TTL level radio carrier directly, the other from a PLL locked to the radio carrier and with a slow loop filter. Both inputs would therefore be at the same frequency but one would be stable at 'mid phase' the other would shift with the instantaneous carrier shift. I'm thinking it might be possible to recover the data from the QE module. Before reinventing the wheel, I wonder if anyone else has already tried this and can share experiences.
Brian.
I have to design a low cost radio time code receiver for use in the UK. It isn't a "wall clock", it has to format the date and time so it fits in a packetized data stream but I can do that easily. There are two radio references I can use, an ASK signal on 60KHz (similar to DCF77) or a 25Hz phase encoded time signal embedded in the UK's "Radio 4" service on 198 KHz. I am leaning toward using 198KHz because the coverage is better and the signal is stronger in most places but the data is harder to decode. Only a few of the modules will be built so it isn't worth designing a custom device but the cost/component count has to be as small as possible.
The idea is to use a PIC with quadrature encoder inputs, one fed from TTL level radio carrier directly, the other from a PLL locked to the radio carrier and with a slow loop filter. Both inputs would therefore be at the same frequency but one would be stable at 'mid phase' the other would shift with the instantaneous carrier shift. I'm thinking it might be possible to recover the data from the QE module. Before reinventing the wheel, I wonder if anyone else has already tried this and can share experiences.
Brian.