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Voice/Control Channel Decoding Software - For discussion of software applications which decode digital voice formats and trunking control channels. Please use the HF Digital Signals forum for anything below 30MHz.

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  #1 (permalink)  
Old 06-29-2015, 3:57 PM
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Question Unitrunker Questions

a few questions regarding Unitrunker (1.0.31.20):
the site i am monitoring uses Motorola (smartzone 851) trunking with P25 digital + analog.

1) are priorities only respected at the beginning of a call, or the middle as well?

2) one channel contains analog voice with Pri 50 of length 10 seconds, and around 2 seconds, another channel has digital voice with Pri 30 of length 3 seconds, what is the expected behavior? should unitrunker switch from the first channel to the second, and then back to the first?

2b) would it be different if the original channel was digital voice instead?

3) does unitrunker only switch to a different channel when it detects P25 voice data (LDU1/2)?
reason: sometimes i see a digital channel (with lower Pri #) flash on and off (on the Site window), but unitrunker remains on the same (analog) channel.

4) is there a way to *follow* a talkgroup on demand?
example: there are multiple activities on the Site window (Call history tab). i hear something interesting and would like to exclusively follow the conversation. is there a way to essentially lock out every other talkgroup such that unitrunker does not switch to other talkgroups?

5) does the user's online status (online, offline, roam) come from the data packet itself, or logistically determined by unitrunker?

6) is there a way to adjust the audio output level of a VCO within unitrunker?
reason: i see some clipping in DSD+'s audio waveform display and was wondering if i can lower the amplitude in unitrunker.

the following questions i've found the answers to:
7) where can i find information on logging?
UniTrunker | Log Files

8) where can i find information on Svc call types?
UniTrunker | Call Activity
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Old 06-30-2015, 1:41 PM
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This will answer a few of your questions.

UniTrunker | Voice Following

Quote:
4) Is there a way to *follow* a talkgroup on demand?
If the call is the voice receiver / VCO's current call, click hold to stick to that call only.

For an arbitrary call, double-click on the group ID (in the history grid or activity panel). Zap the group's priority to 1. Calls to this group should take precedence (assuming no other groups or users are set to 1).

Quote:
5) Does the user's online status (online, offline, roam) come from the data packet itself, or logistically determined by Unitrunker?
It is inferred from control channel activity - events like call grants, registrations, affiliations, and rejections.

Quote:
6) Is there a way to adjust the audio output level of a VCO within unitrunker?
reason: i see some clipping in DSD+'s audio waveform display and was wondering if i can lower the amplitude in Unitrunker.
There's no adjustment for SDR VCOs. The waveform is "normalized" for 16 bit audio at roughly 87% amplitude. You should not see clipping.

You may have additional volume controls within Windows for controlling the audio levels passed through VAC or VB Cable.
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Old 07-01-2015, 12:23 AM
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thank you.
inadvertently i learned about rank & skip.
i never even hovered over the hold button because i assumed it was some sort of pause in processing. oops.

would it make sense to add a manual switching feature?
i see 2 ways to implement it:

1) manual interrupt: user would select a different channel. current call would be skipped, however instead of automatic selection of next call, the selected channel would be played. once the selected call is over, automatic selection is resumed.

2) manual mode: voice VCO remains running, yet parked, until the user manually selects a call. after the call is over, VCO is parked again until the next manual selection.

where i would like to see the manual selection happening is in the Site window > Call History tab, where the top portion shows all the live channel activities.

any thoughts?
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Old 07-01-2015, 1:46 PM
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Quote:
The waveform is "normalized" for 16 bit audio at roughly 87% amplitude. You should not see clipping.
apparently i was not.

to follow up, i used uniscope to examine the virtual line out signal - image attached.

red line added by me.

top left - i assumed the flat portions on top of the waveform were clippings. noted after the fact: peaks do not touch the max (window) limit
top rite - however i noticed similar flats after lowering the volume level.

bottom left - line level increased until clipping occurred. noted:
1) signal touches the upper and lower limits of the window
2) sharp zig-zag lines
bottom rite - line level lowered until no clipping. noted: signal max level (red line) no longer touching the window bounds

i guess the goal is to have black bars above and below the signal, like watching a widescreen movie on a screen with a lower aspect ratio.

PS> any documents on uniscope so i can understand what i'm looking at in Impulse, FFSK, C4FM ?
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Old 07-03-2015, 2:09 PM
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Quote:
Originally Posted by dooshorama View Post
PS> any documents on uniscope so i can understand what i'm looking at in Impulse, FFSK, C4FM ?
You're mostly looking at an eye patterns.

Last edited by Unitrunker; 07-03-2015 at 2:15 PM..
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Old 07-03-2015, 2:15 PM
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Quote:
Originally Posted by dooshorama View Post
where i would like to see the manual selection happening is in the Site window > Call History tab, where the top portion shows all the live channel activities.
I've added your suggestion to the TODO list.
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Old 07-03-2015, 8:51 PM
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Quote:
Originally Posted by dooshorama View Post
red line added by me.

top left - i assumed the flat portions on top of the waveform were clippings. noted after the fact: peaks do not touch the max (window) limit
top rite - however i noticed similar flats after lowering the volume level.

bottom left - line level increased until clipping occurred. noted:
1) signal touches the upper and lower limits of the window
2) sharp zig-zag lines
bottom rite - line level lowered until no clipping. noted: signal max level (red line) no longer touching the window bounds

i guess the goal is to have black bars above and below the signal, like watching a widescreen movie on a screen with a lower aspect ratio.
Squared tops = clipped signal.

Able to draw a straight line across all those tops (even after reducing gain) = clipped signal.

Somewhere in the processing chain, those signals were clipped. Notice how the negative peaks aren't squared and you can't draw a line through them? Those signals weren't clipped on the negative side. The negative side is still intact.

Reducing the gain after a clipping stage still leaves you with a clipped signal...
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Old 07-08-2015, 4:05 PM
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any idea where this clipping may be happening?
and how i can control it?

i tried playing with the receiver gain, but it doesn't seem to make a difference.

i have 2 new observations:

1) squared lowers (smaller attached pic)
2) clipping in Unitrunker VCO scope (bigger attached pic) -- does this mean the signal is getting clipped before it leaves unitrunker?
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Last edited by dooshorama; 07-08-2015 at 4:10 PM.. Reason: curiousity
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Old 07-08-2015, 11:59 PM
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Asymmetric clipping suggests your drift correction is off. Try tweaking the correction value.
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Old 07-09-2015, 8:35 AM
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ooh. outside of the bw. that makes sense.

EDIT> speaking of: how does automatic drift correction work?

Last edited by dooshorama; 07-09-2015 at 8:38 AM.. Reason: Q: link to other thread
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Old 07-11-2015, 9:53 PM
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so i switched the voice VCO receiver to a TCXO with about 1ppm correction factor + auto drift feature off. i am getting mostly symmetrical clippings, but clippings none the less.

i changed the channels' BW to 15khz (from 12.5), but that didn't seem to have any effect.

next, i will try to reproduce the clipping in HDSDR or SDR#.
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Old 07-14-2015, 12:38 PM
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i could not reproduce the clipping in SDR# with 12.5khz BW.

anyway..

unitrunker,
couple questions regarding gain & sampling freq:

1) rtl_test.exe reports a set of "Supported gain values". in a program that utilizes the rtlsdr.dll, the gain is controlled via a slider bar that goes thru the supported values.
in unitrunker, where the gain is entered as an integer, how do you handle a non-supported value? is it rounded up/down?
i.e. here's a partial sub-set of values for my rtl device: 3.7 7.7 8.7 12.5 14.4
what happens if i enter 100 for gain value into unitrunker?

2) is the sampling frequency also limited to a supported set by the rtl device?
i noticed the range used in SDR# is different (.25, .900001, 1.024, 1.4, 1.8, 1.92, 2.048, 2.56, 2.8, 3.2) than what's available in unitrunker (.96, 1.008, 1.024, 1.056, 2.048, 2.112, 2.496, 2.5, 2.56).
any comments on the differences between the sets?
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