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Amateur Radio Data Transmissions - For discussion of all modes used to send data such as APRS and packet.

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Old 11-12-2017, 3:16 PM
   
Join Date: Nov 2017
Location: Christchurch
Posts: 1
Default Pocsag Numeric and RLL

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/...1-I!!PDF-E.pdf
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data transfer, pocsag, rll

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