[aprssig] rino decoding.
wes at kd4rdb.com
Thu Oct 7 22:20:05 CDT 2004
I have started to dig into the rino data format on air.
I connected the DISC out of a 9k6 ready radio and hooked it to my PC's
line input. I recorded some 44.1khz 16 bit wav files of sending my
posit and also of sending an APRS* query.
Analysis of these wav files shows me that I end up with a slightly
different bit rate than Bob B shows on his web site. I measured 1.627mS
between bits or 614 bps.
I also noticed in three of the four recordings I made that the time
between unkeying an initial pulse of one bit when I unkey the mic and
the center of the first data bit is about 286.6mS (175 bit timings) . I
am wondering if the first databit at the release of PTT is a synch. My
four samples yeilded the following times between that first "synch" bit
and the first data bit of 286.62ms,340.45ms,282.13ms and 280.50ms. The
340ms is obviously a fluke, but the radio did it... Perhaps the modem in
the RINO doing the receiving looks for 1 bit, then 175 bits of silence,
and that flags the start of a packet?
Bob, if you read this, can you tell me with any certainty that the data
is exactly 600bps or 614bps? It is entirely possible my sound card is a
little off. 2.33% seems a little much though.... I should have a hand
made 8 bit wav file tomorrow of the APRS* query.
I have a few goals:
1)make an 8 bit wav file that contains cleaned up sounds... no noise,
just the bits.
2)build a PIC processor modem that can read the garmin format on air
from my 9600 capable radio and spit out a standard aprs object packet
suitable to shoot straight into a KISS TNC.
3)Find out if audio coupling can be used or if direct coupling to the
DISC is needed. If this is true, then I could (in theory) play a wave
file by holding my RINO unit near a speaker and poll other rino units
without having to push the Poll menu button.
I have posted the wav files at http://www.kd4rdb.com/aprs/rino/ if
anyone wants to play with them.
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