br0adband
Member
If you're starting DSD+ from the command line, use this:
DSDPlus.EXE -f1 (then press Enter to start it)
That puts DSD+ in a discrete decoding mode where it only looks for and decodes P25 Phase I data streams which can make it work somewhat better than having it listen for any and all formats and then decipher what format it is then kick in the decoding.
The Source Audio display there appears to be getting something but not enough to work with so far. Restart DSD+ using that command above and the -f1 switch, then go into the Recording mixer again, get into the Mic input levels and see if adjusting them up a bit helps. I can't say for sure what you're getting is the proper signal at all from that screenshot, but what you're looking for will obviously be some sort of traffic (even if it's just data and not anything that would decode to a voice) that provides a signal on the DSD+ command line window at the top where that line of hyphens is. That works like a signal strength meter of sorts and as long as it's giving you a reading from about 40 to 70 (median on the entire scale) it should be enough of a signal for DSD+ to work with.
It seems complicated on the surface but in the long run as I mentioned in the last post it's a signal chain:
Signal in the air > pulled in by your Pro-97 > fed by discriminator tap to the computer > with appropriate input levels then passed to DSD+ > decoded for content to provide audible speech > to the computer's speakers = you hear what's going on but because it's a trunked system your current setup means you'll miss out on comms when they hop trunks/channels.
With an RTL stick aka a "cheap USB TV tuner" you can buy for $10-20 that then gets added into this chain as follows and functions (and I'll highlight what the RTL stick adds):
Signal in the air > pulled in by your Pro-97 > fed by discriminator tap to the computer > with appropriate input levels then passed to Unitrunker for (Signal receiver) decoding and following the trunking properly > Unitrunker then can be used to control the RTL stick as the actual voice channel tuner which means it'll follow conversations if you hold on a specific talkgroup > that digital signal received by the RTL stick is fed from Unitrunker (Voice receiver) to DSD+ > decoded for content to provide audible speech > to the computer's speakers = you hear what's going on properly with trunk tracking working as it should be done
That makes sense, right?
Seems complicated on the surface, but relatively easy to actually make a reality. You've obviously got two of the tools needed: a tapped scanner and a computer running the software (Unitrunker, like DSD+, is also free) - the third tool to give you an actual P25 Phase I monitoring setup would be one of those RTL sticks at fairly minimal pricing and voila, that Tallahassee/Leon system then becomes something you can actually monitor again without having to put out a pocket of cash to make a reality.
I don't even own a physical scanner anymore (think I mentioned that already, can't even remember) and all I own are two of those RTL sticks, combined cost was $20 + shipping, and some home made antennas I've created (an 800 MHz 1/4 wave ground plane from coat hangers and an SO-239 chassis mount as well as some duckies including the Radio Shack 800 MHz because it's just awesome, period). I use those two sticks for all my monitoring of everything in the Las Vegas metropolitan area with my laptop (has a docking station that adds 5 more USB ports on top of the 4 my laptop already has) and I use the RTL sticks with 8 foot USB extension cords to keep them away from the computer itself (RFI protection, as well as having ferrite cores wrapped around the USB cords too).
All in all the whole thing works remarkably well, surprisingly. I only have two P25 systems here in my area that are active and interesting to me: one is Nellis AFB, and the other is a newer changeover system (they're moving from analog to P25) - in about 2 mins time I created a new "system" using Unitrunker and DSD+ that lets me monitor the second P25 system. It doesn't have any of the talkgroup info programmed in yet because I literally just created it. One RTL stick is a Signal receiver for Unitrunker meaning it's used strictly for the control channel of the P25 system and tunes only that frequency. The second stick is the Voice receiver and it receives instructions from Unitrunker on which frequency to tune in when a new transmission occurs - when that happens, the audio data is passed on to DSD+ using a virtual audio cable (ain't gonna get into that now) in the Windows audio mixer where DSD+ decodes it and provides me with the actual decoded speech audio.
2 mins, and it works. Screenshot:
It ain't perfect, it doesn't sound as good as it can (DSD+ offers options for tuning the decodes to clean them up and provide better audio quality), and it's a mish-mash of applications to make it happen but it actually does work and in some respects I have more capabilities available to me than any digital scanner can at this point regardless of the price. It's not for everyone, no, but it's fun to experiment and try new things.
Having a handheld is just the beginning these days, adding computers, SDR hardware and software, and it becomes practically a new hobby all by itself.
EDIT:
With respect to the antennas, I would say use the Pro-97's signal strength meter to give you an idea of which one provides the best signal on the primary control channel frequency of 857.46250 (that would be one you will eventually lock out since it's just a data stream 24/7). I would suspect that the adjustable whip antenna will work the best - the stock rubber ducky is better for VHF and UHF stuff (in the 118 to 512 MHz range) - the Diamond antenna there (at least that's what it appears to be, the RH-C77A which I have myself) is designed for dual band operation in the 144 MHz and 440 MHz bands but it does work remarkably well as a wideband receive antenna as well, mostly in the same range the stock ducky has but it will actually get 700-900 MHz content too, just not as sensitive in those bands.
The adjustable whip antenna could be tuned to roughly 855 MHz (right in the middle of the 800 MHz public service range) and work the best overall but you'll have to figure out how to adjust it to the proper length. I can tell you that a half wave 855 MHz antenna would be about 6.5" long but that whip you have (looks like the traditional Radio Shack adjustable whip they've been selling since the 1980s) has the loading coil which means it affects how the tuning works. Best suggestion: try using the adjustable whip antenna and setting it for about 7" long, check the signal strength then adjust it longer and shorter and see if things change in terms of the signal reception.
Placing is also going to affect your reception meaning where you're located in your home at the time. If you're using all this stuff with the computer (I don't know if you have a desktop or a laptop) trying to get the antenna situated near a window in the direction of the tower - the actual tower information is here: http://www.radioreference.com/apps/db/?siteId=16149 so you can look at the map there and zoom in and find out exactly where those signals are coming from in your area, down to basically the street intersection and then adjust things accordingly to get the best line-of-sight type signal you can.
Hope this helps...
EDIT 2:
Can't believe I missed this but but but... use that primary control channel as your test frequency: when you tune that frequency in and pipe that signal through the tap to DSD+ it's going to decode it as a P25 Phase I control channel because that's what it actually is. You won't hear any voice coming out at any time since it's a pure data stream but at least you'll be able to use that as your "test bed" signal to ensure that DSD+ is getting one at all and then adjust the levels accordingly. All you should see will be something like this when DSD+ is decoding a P25 Phase I control channel:
That's all you should see, endlessly scrolling by line after line after line. You may notice occasional changes to the NAC depending on the system and how it handles things, but typically it'll just stay on the same NAC over and over. The control channel will provide you with a fairly rock solid signal that doesn't deviate much at all and is a reliable source to get DSD+ working properly. If and when that happens you can then lock out the CC frequency and start tuning the other 43 that appear to be in use for that system and sooner or later you'll start hearing tidbits of voices, hopefully.
DSDPlus.EXE -f1 (then press Enter to start it)
That puts DSD+ in a discrete decoding mode where it only looks for and decodes P25 Phase I data streams which can make it work somewhat better than having it listen for any and all formats and then decipher what format it is then kick in the decoding.
The Source Audio display there appears to be getting something but not enough to work with so far. Restart DSD+ using that command above and the -f1 switch, then go into the Recording mixer again, get into the Mic input levels and see if adjusting them up a bit helps. I can't say for sure what you're getting is the proper signal at all from that screenshot, but what you're looking for will obviously be some sort of traffic (even if it's just data and not anything that would decode to a voice) that provides a signal on the DSD+ command line window at the top where that line of hyphens is. That works like a signal strength meter of sorts and as long as it's giving you a reading from about 40 to 70 (median on the entire scale) it should be enough of a signal for DSD+ to work with.
It seems complicated on the surface but in the long run as I mentioned in the last post it's a signal chain:
Signal in the air > pulled in by your Pro-97 > fed by discriminator tap to the computer > with appropriate input levels then passed to DSD+ > decoded for content to provide audible speech > to the computer's speakers = you hear what's going on but because it's a trunked system your current setup means you'll miss out on comms when they hop trunks/channels.
With an RTL stick aka a "cheap USB TV tuner" you can buy for $10-20 that then gets added into this chain as follows and functions (and I'll highlight what the RTL stick adds):
Signal in the air > pulled in by your Pro-97 > fed by discriminator tap to the computer > with appropriate input levels then passed to Unitrunker for (Signal receiver) decoding and following the trunking properly > Unitrunker then can be used to control the RTL stick as the actual voice channel tuner which means it'll follow conversations if you hold on a specific talkgroup > that digital signal received by the RTL stick is fed from Unitrunker (Voice receiver) to DSD+ > decoded for content to provide audible speech > to the computer's speakers = you hear what's going on properly with trunk tracking working as it should be done
That makes sense, right?
Seems complicated on the surface, but relatively easy to actually make a reality. You've obviously got two of the tools needed: a tapped scanner and a computer running the software (Unitrunker, like DSD+, is also free) - the third tool to give you an actual P25 Phase I monitoring setup would be one of those RTL sticks at fairly minimal pricing and voila, that Tallahassee/Leon system then becomes something you can actually monitor again without having to put out a pocket of cash to make a reality.
I don't even own a physical scanner anymore (think I mentioned that already, can't even remember) and all I own are two of those RTL sticks, combined cost was $20 + shipping, and some home made antennas I've created (an 800 MHz 1/4 wave ground plane from coat hangers and an SO-239 chassis mount as well as some duckies including the Radio Shack 800 MHz because it's just awesome, period). I use those two sticks for all my monitoring of everything in the Las Vegas metropolitan area with my laptop (has a docking station that adds 5 more USB ports on top of the 4 my laptop already has) and I use the RTL sticks with 8 foot USB extension cords to keep them away from the computer itself (RFI protection, as well as having ferrite cores wrapped around the USB cords too).
All in all the whole thing works remarkably well, surprisingly. I only have two P25 systems here in my area that are active and interesting to me: one is Nellis AFB, and the other is a newer changeover system (they're moving from analog to P25) - in about 2 mins time I created a new "system" using Unitrunker and DSD+ that lets me monitor the second P25 system. It doesn't have any of the talkgroup info programmed in yet because I literally just created it. One RTL stick is a Signal receiver for Unitrunker meaning it's used strictly for the control channel of the P25 system and tunes only that frequency. The second stick is the Voice receiver and it receives instructions from Unitrunker on which frequency to tune in when a new transmission occurs - when that happens, the audio data is passed on to DSD+ using a virtual audio cable (ain't gonna get into that now) in the Windows audio mixer where DSD+ decodes it and provides me with the actual decoded speech audio.
2 mins, and it works. Screenshot:
It ain't perfect, it doesn't sound as good as it can (DSD+ offers options for tuning the decodes to clean them up and provide better audio quality), and it's a mish-mash of applications to make it happen but it actually does work and in some respects I have more capabilities available to me than any digital scanner can at this point regardless of the price. It's not for everyone, no, but it's fun to experiment and try new things.
Having a handheld is just the beginning these days, adding computers, SDR hardware and software, and it becomes practically a new hobby all by itself.
EDIT:
With respect to the antennas, I would say use the Pro-97's signal strength meter to give you an idea of which one provides the best signal on the primary control channel frequency of 857.46250 (that would be one you will eventually lock out since it's just a data stream 24/7). I would suspect that the adjustable whip antenna will work the best - the stock rubber ducky is better for VHF and UHF stuff (in the 118 to 512 MHz range) - the Diamond antenna there (at least that's what it appears to be, the RH-C77A which I have myself) is designed for dual band operation in the 144 MHz and 440 MHz bands but it does work remarkably well as a wideband receive antenna as well, mostly in the same range the stock ducky has but it will actually get 700-900 MHz content too, just not as sensitive in those bands.
The adjustable whip antenna could be tuned to roughly 855 MHz (right in the middle of the 800 MHz public service range) and work the best overall but you'll have to figure out how to adjust it to the proper length. I can tell you that a half wave 855 MHz antenna would be about 6.5" long but that whip you have (looks like the traditional Radio Shack adjustable whip they've been selling since the 1980s) has the loading coil which means it affects how the tuning works. Best suggestion: try using the adjustable whip antenna and setting it for about 7" long, check the signal strength then adjust it longer and shorter and see if things change in terms of the signal reception.
Placing is also going to affect your reception meaning where you're located in your home at the time. If you're using all this stuff with the computer (I don't know if you have a desktop or a laptop) trying to get the antenna situated near a window in the direction of the tower - the actual tower information is here: http://www.radioreference.com/apps/db/?siteId=16149 so you can look at the map there and zoom in and find out exactly where those signals are coming from in your area, down to basically the street intersection and then adjust things accordingly to get the best line-of-sight type signal you can.
Hope this helps...
EDIT 2:
Can't believe I missed this but but but... use that primary control channel as your test frequency: when you tune that frequency in and pipe that signal through the tap to DSD+ it's going to decode it as a P25 Phase I control channel because that's what it actually is. You won't hear any voice coming out at any time since it's a pure data stream but at least you'll be able to use that as your "test bed" signal to ensure that DSD+ is getting one at all and then adjust the levels accordingly. All you should see will be something like this when DSD+ is decoding a P25 Phase I control channel:
That's all you should see, endlessly scrolling by line after line after line. You may notice occasional changes to the NAC depending on the system and how it handles things, but typically it'll just stay on the same NAC over and over. The control channel will provide you with a fairly rock solid signal that doesn't deviate much at all and is a reliable source to get DSD+ working properly. If and when that happens you can then lock out the CC frequency and start tuning the other 43 that appear to be in use for that system and sooner or later you'll start hearing tidbits of voices, hopefully.
Last edited:
