Decidng p25 question

Status
Not open for further replies.

Dog

Member
Premium Subscriber
Joined
Jun 3, 2003
Messages
252
Location
Oklahoma
In the signal VCO you have the park frequency as 856.5000 that frequency isn't listed anywhere on that site.

It shows up as a Motorola system however I don't believe it is the system you are trying to listen to. 856.5000 isn't listed for any system in North Carolina.

The control frequencies listed are 858.1375 main 857.4375 alternate 859.437 alternate 858.4375 alternate.

Try those and see if you find a control channel.
 

trauts14

Member
Joined
Dec 19, 2010
Messages
223
darn, i set the park to 856.000 since it was sort of the middle freq in the range of freqs that system uses. i did not think about setting the park to the control. thanks. i will try that
 

Dog

Member
Premium Subscriber
Joined
Jun 3, 2003
Messages
252
Location
Oklahoma
At the top of the site window the signal should go solid green. You should see talk group IDs start showing in the "Listen" section of the voice VCO.

With one dongle you may have to set the park frequency of the voice VCO to something like 856.0000 like you had the other one before I am not sure.
 

br0adband

Member
Joined
Apr 8, 2005
Messages
1,569
Location
Springfield MO
As something to check: make sure all the Windows audio mixer settings across the board are set so that everything is working at 16 bit 48 kHz - DSD+ will only decode properly if you're feeding it audio based on those parameters, you'll have to go into the Windows mixer (right-click the speaker icon and choose Playback devices first), double-click each device listed (can't hurt to make sure everything is working on the same basis) and for each device make sure the Advanced tab shows the Default Format is 16 bit, 48000 Hz (DVD Quality) for every device.

As a tip: I'd suggest using VB-Audio Virtual Audio Cable (a donationware product) instead of what you appear to be using (Virtual Audio Cable, a commercial product). It's not about the price, mind you, there's a chance you paid for VAC and find it useful, but in my own experience the fact that it's not a simple "install it and go" product which does require some configuration which has to be very precise often causes more problems than it's worth. VB-Audio Virtual Audio Cable is very simple: install it, and... well that's pretty much it aside from making sure it too is set for 16 bit 48 kHz operation in the Windows audio mixer.

I spent an hour working with VAC in the past (I know it has a trial period so I did that to become familiar with it to help others) and found it lacking and just not worth the hassles and the configuration necessary.

For me, VB-Audio Cable just works, period, and I've never had an issue with it. On a clean machine that has never been used with any SDR software or hardware at all I can install the Zadig drivers for an RTL stick, VB-Audio Virtual Audio Cable A (since only one is required but there's a second one, B, also available if needed), SDR#, Unitrunker, DSD+, and be monitoring something -even digital comms - in under 3 minutes and I've done it several times for other people - it's shocking that it can be that "easy" to them because they'll probably have stumbled along with instructions from 15 sources and it confuses them which is understandable.

Of course I've done this so often these days it's second nature to me so I can't blame people new to using this software and hardware if they're having issues, most of the instructions out there are lacking pretty severely so, asking for help is obviously a necessity in these kinds of situations.

Anyway, the two tips above should prove useful, at least that's the hope. ;)
 

trauts14

Member
Joined
Dec 19, 2010
Messages
223
@Dog it appears with one dongle i needed it parked at the 856.000 freq i was using. the 4 controls did nothing and the site window never came up. i have a solid green status bar on the site window and i can see calls moving around. i do not have any activity as you mentioned in the "Listen" section" of the voice VCO.
below are 2 current screenshots. the Voice VCO should not have a frequency set under the "Listen" section???
 

Attachments

trauts14

Member
Joined
Dec 19, 2010
Messages
223
this is from my Site window. it is showing the control on its own at 856.4875.....i did not enter that. i still cannot hear anything. should i hear some audio without DSD+ running?
 

Attachments

trauts14

Member
Joined
Dec 19, 2010
Messages
223
@br0adband thank you. i did confirm all audio devices were set to what you recommended. i am not opposed to removing VAC and installing VB. i am not sure exactly what i will need to change within unitrunker (im using 1 dongle) to change the settings to make VB play nice.
 

trauts14

Member
Joined
Dec 19, 2010
Messages
223
here is another screenshot from "Site" window. unitrunker is detecting the control channels. i leads me to believe my issue is a simple audio line issue maybe. if that is the case, hopefully it will be simple to address as opposed to deleting my virtual aduio cable and trying the one @br0adband suggested. i hope it is a simple issue at least.
 

Attachments

Dog

Member
Premium Subscriber
Joined
Jun 3, 2003
Messages
252
Location
Oklahoma
@Dog it appears with one dongle i needed it parked at the 856.000 freq i was using. the 4 controls did nothing and the site window never came up. i have a solid green status bar on the site window and i can see calls moving around. i do not have any activity as you mentioned in the "Listen" section" of the voice VCO.
below are 2 current screenshots. the Voice VCO should not have a frequency set under the "Listen" section???
this is from my Site window. it is showing the control on its own at 856.4875.....i did not enter that. i still cannot hear anything. should i hear some audio without DSD+ running?
You don't have the voice VCO parked on 856.0000,

Can you post a screenshot of the signal VCO?

If you uncheck mute on the signal receiver do you hear the control channel data? Also listen to it for a couple of minutes, I don't remember if the free version has a advertising voice over or not. If the green bar stays green it should be fine.

You should hear something without DSD+ if there are analog communications.I don't know how active they are on your system though,
 

trauts14

Member
Joined
Dec 19, 2010
Messages
223
i thought only the signal VCO needed to be parked on 856.500. i did not know the VOICE VCO also had to be parked on the same freq. i will start with that and send screenshots and do what you mentioned.
 

trauts14

Member
Joined
Dec 19, 2010
Messages
223
If i mute VOICE VCO I hear control channel audio. if i unmute voice vco and mute signal VCO i hear control channel audio. the green bar is solid green. im not hearing trunked comms from the PD but i guess i am in stepping in the right direction.
 

Attachments

br0adband

Member
Joined
Apr 8, 2005
Messages
1,569
Location
Springfield MO
Unitrunker will provide the analog audio of the control channel without issues direct to your sound card - the virtual audio cable is not part of that signal path whatsoever when things are working correctly - so it's normal to be able to hear that aspect of this hence keeping it muted since it's not something we humans really need to hear or could interpret in real-time anyway. ;)
 

Dog

Member
Premium Subscriber
Joined
Jun 3, 2003
Messages
252
Location
Oklahoma
The signal receiver needs to be set to the control channel.

With one dongle the dongle tunes to the signal VCO parked frequency (control channel) so Unitrunker can decode the information. when Unitrunker sees a call it changes the frequency of the dongle to the voice channel to listen to the radio transmission. When the transmission ends it switches back to the signal VCO parked frequency (control channel) to listen for more calls.

Someone with more experience with one dongle will need say what the voice VCO parked frequency needs to be set to. Either 0.000, A frequency somewhere in the middle 856, or the control frequency.

You are very close. Don't give up.
 

trauts14

Member
Joined
Dec 19, 2010
Messages
223
Thanks Dog. I will plug in the control freqs as "park" this afternoon and try again. It seems since I am using one dongle I am in the minority. Making a P25 decoding scanner for $20 is a great deal and a helluva a learning experience.
Once I get it running and fully understand it, I want to make my own private live feed which is going to be another learning experience. at least i understand web servers.
 

SCPD

QRT
Joined
Feb 24, 2001
Messages
65,126
Location
Virginia
Hello trauts;

Your signal role VCO looks good. Your site window shows good decode rate and decent hit counts for the voice channels.

Sadly, your voice role VCO won't be able to do much. Most of the voice channels are more than 2 Mhz away from the control channel. This exceeds the usable bandwidth of your Realtek.

You will need to purchase a second SDR device. Another Realtek should work fine. You can configure both devices to have just one VCO each.
 

trauts14

Member
Joined
Dec 19, 2010
Messages
223
Thank you for the assistance. For testing purposes since I have everything working (so it seems), i should be able to hear something occasionally with my current setup, correct? i actually have a second rtl-sdr dongle that arrives monday.
 

SCPD

QRT
Joined
Feb 24, 2001
Messages
65,126
Location
Virginia
Yes trauts14 - but you might have to wait a very long time. The only channels that are within the 2 Mhz usable bandwidth of the active control channel are the three alternate control channels. The system will use these for voice traffic only when the other voice channels are busy. So on a very busy day, you may hear some calls.
 
Status
Not open for further replies.
Top