Pocsag Numeric and RLL

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glinders

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Nov 12, 2017
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Christchurch
Hi There,

I am trying to send binary data over pocsag numeric. This works fine until I try to send a sequence 0xfffff (five times 0xF or more).

Because of an unfortunate coincidence, this sequence is sent over the line as 0xffffffff. There is a 10 bit BCH code and a parity included in the codeword.

The receiver however chokes on this because the bandwidth of the receiver can 't go that low. This codeword is sent as carrier + frequency deviation for the channel, so there is no way the receiver can sync again with the transmitter.

I looked at the pocsag specification (*) and there is no mention of RLL (https://en.wikipedia.org/wiki/Run-length_limited) or any other way to limit the number of consecutive zeros or ones transmitted over the air.

Is there anyone who has experienced the same problem and is there a workaround for it?

(*) http://www.itu.int/dms_pubrec/itu-r/rec/m/R-REC-M.584-2-199711-I!!PDF-E.pdf
 
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