31-03-2019, 10:29
Hi,
I have to agree with TassyJim on both duty cycle and power level aspects. The 433 MHz "ISM band" is basically a single-channel (433.92 MHz frequency) system which relies heavily on "time sharing". Many countries' regulations recommend a maximum average duty cycle of just 1% and rarely as high as 10%. As Werk notes, most (all?) 433 MHz commercial systems do (must) transmit the gust data as a separate data field within lower-duty-cycle packets.
AFAIK, Davis does not use the 433 MHz ISM band at all, but also they use a "spread spectrum" (channel-hopping) technique to avoid "blocking" any particular channel. In America, they use the "915 MHz" band from 902 - 928 MHz and in Europe/UK the "868 MHz" band. It appears that neither of these bands is permitted in Australia, so Davis supply a special version which channel-hops within a band from 915 - 928 MHz. See the information particularly from Prodata in this Cumulus thread.
My Medium/Long-term aims are to implement a gust-packet within the Weatherduino format, but an alternative (to reduce both the transmitter duty cycle and power drain) is to use the Auriol (Weatherduino-compatible) protocol. However, I haven't yet been able to find a specification of the (Wind) transmission period within the wireless protocol documentation.
Cheers, Alan.
(29-03-2019, 05:09)TassyJim Wrote: One packet takes 380mS and sending that every 3 seconds was too high a duty cycle for me. I have other RF data links also on 433MHz and I am worried about interference.
I have to agree with TassyJim on both duty cycle and power level aspects. The 433 MHz "ISM band" is basically a single-channel (433.92 MHz frequency) system which relies heavily on "time sharing". Many countries' regulations recommend a maximum average duty cycle of just 1% and rarely as high as 10%. As Werk notes, most (all?) 433 MHz commercial systems do (must) transmit the gust data as a separate data field within lower-duty-cycle packets.
AFAIK, Davis does not use the 433 MHz ISM band at all, but also they use a "spread spectrum" (channel-hopping) technique to avoid "blocking" any particular channel. In America, they use the "915 MHz" band from 902 - 928 MHz and in Europe/UK the "868 MHz" band. It appears that neither of these bands is permitted in Australia, so Davis supply a special version which channel-hops within a band from 915 - 928 MHz. See the information particularly from Prodata in this Cumulus thread.
My Medium/Long-term aims are to implement a gust-packet within the Weatherduino format, but an alternative (to reduce both the transmitter duty cycle and power drain) is to use the Auriol (Weatherduino-compatible) protocol. However, I haven't yet been able to find a specification of the (Wind) transmission period within the wireless protocol documentation.
Cheers, Alan.