I am in progress of making a analog FM <-> P25 digital voice gateway out of a Astro Saber.
Before starting to dig it myself, has someone already found a place where a logical signal is found for P25 signal COS? So a signal that goes up or down when the radio is receiving a P25 signal.
Thanks,
Erik
digital voice COS from astro saber
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Re: digital voice COS from astro saber
I have something similar, but mine is an astro xts to a 900 MHz digital speaker mic wireless link.
Since there is no CSQ on the XTS series UDC I use the received audio output which is fed from a 100K pot thru a .47 uf coupling cap of which the other end of the cap goes to the anode of a Schottky diode and the cathode of this diode is fed into a shunt load.
This shunt load consists of a 100K resistor and a 4.7 uf cap which gives about a 330 ms hold time.
The entire circuit with a simple software debounce and hold routine has a fast enough attack time and medium decay time to where no audio is lost.
I then fed the Schottky diodes shunt output, RC network, to a PIC processors input pin which does my T/R logic selection.
Just Set the radios audio output thru the 100 K pot so that the PIC input is never above ~4 volts and it works nicely, if you want to be extra safe you can clamp the PICs input pin with a 3 to 4.7 volt zener so that you can never overdrive the PIC processors 5 volt logic level input no matter what level the Astro radios audio is set to.
Mike
Since there is no CSQ on the XTS series UDC I use the received audio output which is fed from a 100K pot thru a .47 uf coupling cap of which the other end of the cap goes to the anode of a Schottky diode and the cathode of this diode is fed into a shunt load.
This shunt load consists of a 100K resistor and a 4.7 uf cap which gives about a 330 ms hold time.
The entire circuit with a simple software debounce and hold routine has a fast enough attack time and medium decay time to where no audio is lost.
I then fed the Schottky diodes shunt output, RC network, to a PIC processors input pin which does my T/R logic selection.
Just Set the radios audio output thru the 100 K pot so that the PIC input is never above ~4 volts and it works nicely, if you want to be extra safe you can clamp the PICs input pin with a 3 to 4.7 volt zener so that you can never overdrive the PIC processors 5 volt logic level input no matter what level the Astro radios audio is set to.
Mike