[Repeater-Builder] Analog Repeater to APCO25 conversion?
You might want to check this new controller out. If/When they pull this one off, it's going to change the game considerably!! http://www.ercsystem.com/s/applications.shtml Pay particular attention to paragraph about 2/3 of the way down... WebMaster for the Cheshire County DX ARC, Located at: http://www.ccdx.org See Ya, Joel wa1...@ccdx.org or WA1ZYX > K1XX DxCluster Node (Amateur Radio) http://www.ccdx.org/zedyx/home.htm http://home.webryders.net/surry 443.800 141.3 Keene, NH --- 449.450 123.0 Saddleback Mtn 449.875 123.0 Cannon Mtn 447.425 141.3 Temple Mtn 53.730 141.3 Keene WinErr: 079 Mouse not found -- A mouse driver has not been installed. Please click the left mouse button to continue
Re: [Repeater-Builder] Analog Repeater to APCO25 conversion?
kt...@ameritech.net wrote: > I'm wondering if anyone has thought about or attempted to modify an > analog repeater to regenerate P25 signalling (C4FM)? I know the easy > way would be to buy a Quantar or similar box, or tying two mobiles > back-to-back for flat-audio passthru. > > I want to find a way to recover the phase-modulated signalling, > passing it to a homebrew "logic" board. This board would stream the > bits into memory and if the NAC is valid, then regenerate the > similiar stream out the transmitter. You could also store-and-forward > this "audio" to other systems or for playback. So I either need to > buy a manual to read the theory or ask here if anyone has tinkered > with this. Maybe I'm missing something here, but isn't > phase-modulation not quite the same as our VCO-modulated direct FM? > P25 as I understand it, either shifts the phase 600Hz or 1800Hz plus > or minus, and based on this generates a two-bit "symbol" at 9600 > baud. Error: P25 is direct FM-actually true FSK. Phase-modulated transmitters won't work with P25.
[Repeater-Builder] Analog Repeater to APCO25 conversion?
I'm wondering if anyone has thought about or attempted to modify an analog repeater to regenerate P25 signalling (C4FM)? I know the easy way would be to buy a Quantar or similar box, or tying two mobiles back-to-back for flat-audio passthru. I want to find a way to recover the phase-modulated signalling, passing it to a homebrew "logic" board. This board would stream the bits into memory and if the NAC is valid, then regenerate the similiar stream out the transmitter. You could also store-and-forward this "audio" to other systems or for playback. So I either need to buy a manual to read the theory or ask here if anyone has tinkered with this. Maybe I'm missing something here, but isn't phase-modulation not quite the same as our VCO-modulated direct FM? P25 as I understand it, either shifts the phase 600Hz or 1800Hz plus or minus, and based on this generates a two-bit "symbol" at 9600 baud. So please don't flame and say "Go buy a Quantar" because if this could be done, many surplus systems could be modified for new digital modes. Any help with schematic scans or what part numbers for Astro/Quantar style unit manuals would be welcomed. Thanks! Tony
