I am comforatable with my prospects once I have that bit stream...it is plugging the pieces together to get to that point that I am having trouble with.
On 4/15/06, Frank Brickle <[EMAIL PROTECTED]> wrote: > If you poke around the net, you will probably be able to find the source > for an old DOS program that decodes EDACS control channel. It's called > "Trunk Tracker." > > I also have original source for an EDACS control channel decoder of my > own from a number of years ago. Unfortunately all that remains is a > hardcopy, but if you want, I can scan and provide that, probably. > > Both of these assume that the demod and bitsync have been performed > already and are being fed to their inputs as binary streams. > > Frank > > Ryan Pape wrote: > > Finally having all the pieces in place I need, I want to use the new > > GMSK code to decode an EDACS trunked radio control channel. > > > > > > Given my rudimentary knowledge on the topic (and gnuradio in general) > > which (if any) of the examples present would be my best starting point > > given that I'm hoping to do this, even initially, right off the air > > with the TV RX? > > > > Some details at > > http://users.netropolis.net/maverick/scanners/edacs.htm for anyone > > interested. > > > > Most relevant snippet for the uninitiated: > > ~~~~ > > > > Modulation: It looks like GMSK (Gaussian Minimum Shift Keying) which > > is basically the same thing as two level FSK keying except that the > > data stream is passed through a low pass filter before modulating the > > carrier. This reduces the high frequency components allowing the > > control channel to fit within a 12.5KHz channel. Accordingly, a simple > > data-slicer circuit can be used to receive the control channel > > information. > > > > Baud Rate > > 9600 Baud > > Frame Sync > > Frame synchronization is achieved by sending the following 48 bit > > sequence: > > 000101010101010101010111000100100101010101010101 > > or > > 0x155557125555 Hexadecimal > > Data Frames > > After transmission of the frame synchronization sequence TWO data > > frames will be transmitted and then the whole cycle repeats ad > > infinitum. Each data frame is 120 bits long; this means 288 bits are > > transmitted in each cycle (2x120 bits for the data frames and 48 bits > > for frame sync). > > > > > > _______________________________________________ > > Discuss-gnuradio mailing list > > [email protected] > > http://lists.gnu.org/mailman/listinfo/discuss-gnuradio > > > > > > _______________________________________________ Discuss-gnuradio mailing list [email protected] http://lists.gnu.org/mailman/listinfo/discuss-gnuradio
