Frequency Hopping

As mentioned in my last entry I was toying with the idea of frequency hopping on the RF side of things, well looks like someone has implemented something similar here http://www.raccoonrezcats.com/rfmodem.html I’ll like to do something similar to this as it seems doable. 

While not able to get some “hands on” development time over the weekend, I did more reading of the HopeRF modules and these will be able to achieve the hopping, as the can programmed to any frequency in the 902-928Mhz Freq range so definately looking achievable.

If what the above links says on the site then we could (at least in theory) have a max output of 1watt if we chose to implement hopping, else we are limited to 1mW output power.

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Author: Stephen Eaton

Geek at heart. Loves to tinker and find out how things work, which inevitably leads to items in pieces and not working for much longer :)

7 thoughts on “Frequency Hopping”

  1. how many channels can we achieve in the rfm12b , i have used the rfm12b-915 . i see its frequency ranges from 900 to 929 in 7.5Khz steps but have tested on two frequencies 914 and 922 , but there has to be band gap due to frequency deviation ,how much channels can i achieve ? . i will then move on to 433Mhz for greater range. but i think the channels will reduce. it has 2.5Khz steps.

  2. It all depends on the bit rate you select as the deviation and bandwidth are different for each datarate. The main thing is the bandwidth as deviation needs to be less than the bandwidth, so use bandwidth in your calc.

    bps channels Dev(khz)BW (khz)
    @9600 60 75 134
    @19200 52 75 134
    @38400 45 90 200
    @57600 37 105 270
    @115200 29 180 340

    Channel 9600 19200 38400 57600 115200
    1 900.84 900.84 900.84 900.84 900.84
    2 901.32 901.40 901.49 901.62 901.85
    3 901.80 901.95 902.13 902.40 902.85
    4 902.28 902.51 902.78 903.18 903.86
    5 902.76 903.06 903.42 903.96 904.86
    6 903.24 903.62 904.07 904.74 905.87
    7 903.72 904.17 904.71 905.52 906.87
    8 904.20 904.73 905.36 906.30 907.88
    9 904.68 905.28 906.00 907.08 908.88
    10 905.16 905.84 906.65 907.86 909.89
    11 905.64 906.39 907.29 908.64 910.89
    12 906.12 906.95 907.94 909.42 911.90
    13 906.60 907.50 908.58 910.20 912.90
    14 907.08 908.06 909.23 910.98 913.91
    15 907.56 908.61 909.87 911.76 914.92
    16 908.04 909.17 910.52 912.54 915.92
    17 908.52 909.72 911.16 913.32 916.92
    18 909.00 910.28 911.81 914.10 917.93
    19 909.48 910.83 912.45 914.88 918.93
    20 909.96 911.39 913.10 915.66 919.94
    21 910.44 911.94 913.74 916.44 920.94
    22 910.92 912.50 914.39 917.22 921.95
    23 911.40 913.05 915.04 918.00 922.95
    24 911.88 913.61 915.68 918.78 923.96
    25 912.36 914.16 916.32 919.56 924.96
    26 912.84 914.72 916.97 920.34 925.97
    27 913.32 915.27 917.61 921.12 926.97
    28 913.80 915.83 918.26 921.90 927.98
    29 914.28 916.38 918.90 922.68 928.99
    30 914.76 916.94 919.55 923.46
    31 915.24 917.49 920.19 924.24
    32 915.72 918.05 920.84 925.02
    33 916.20 918.60 921.48 925.80
    34 916.68 919.16 922.13 926.58
    35 917.16 919.71 922.77 927.36
    36 917.64 920.27 923.42 928.14
    37 918.12 920.82 924.06 928.92
    38 918.60 921.38 924.71
    39 919.08 921.93 925.35
    40 919.56 922.49 926.00
    41 920.04 923.04 926.64
    42 920.52 923.60 927.29
    43 921.00 924.15 927.93
    44 921.48 924.71 928.58
    45 921.96 925.26 929.22
    46 922.44 925.82
    47 922.92 926.37
    48 923.40 926.93
    49 923.88 927.48
    50 924.36 928.04
    51 924.84 928.59
    52 925.32 929.15
    53 925.80
    54 926.28
    55 926.76
    56 927.24
    57 927.72
    58 928.20
    59 928.68
    60 929.16

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