DMA P25 Decoding and Audio Issues
From The RadioReference Wiki
How can I adjust for the distortion/underwater sounds I hear on the digital trunktrackers?
Some voices are soft, others are loud. How can I fix this?
- Adjusting the P25 Decode Level
- Digital End Code detection
- Simulcast digital distortion
- Adjusting the AGC
My audio is cutting out every couple of seconds. What is wrong?
- You probably have one of the priority features turned on.
- Close Call Priority -- audio will cut out every 2 seconds on all systems. If your model supports it, check out Close Call Do-Not-Disturb to keep the Close Call feature but lose the "gap."
- Weather Prioirty -- audio will cut out every 5 seconds on all systems.
- Conventional Priority -- audio will cut out every 2 seconds only on Conventional systems (that time is user configurable).
- Another thing that causes audio cutouts is CTCSS or DCS, also known as "PL tone". If audio cuts out on a conventional channel with CTCSS, try changing the modulation setting to "FM" instead of "NFM". If the signal is weak, you may need to lower the squelch setting too.
- On the BCT15, the bear tracker warning system (bear claw icon) will also cause your audio to cut out every two seconds when active (thanx KB3JNX)
I hear popping or thumping (from the scanner speaker) (from PC speakers). How do I stop this?
I hear a hum coming from the speakers even with nothing received
- From the scanner speaker - This comes from the audio amp cycling on/off during scanning. It's likely a little DC is leaking into the audio chain at the time the amp is cycling.
- To a PC - with or w/o additional cables, such as Serial/USB to scanner attached and AC or DC Power applied to the Speaker or PC - the solution is the same - Add one of the following ground loop isolator to the audio line. The likely cause is a large and long ground loop issue. The first item is easier to obtain; use only side of the pair of jacks. i.e. white and white without red connected at all. The problem and solution is discussed herein this article. *Other distributors exist for similarly named products.
I had a speaker plugged into the speaker out, but when I unplug it I get no audio. What has happened?
- There is a known issue with the earphone jack. It may require a return to Uniden to fix, you may try a small non-conductive item like a toothpick or shoelace tip to push audio jack back down, unless you are handy with disassembling the scanner to get to the jack to manually reset it.
I had a PC sound card plugged into the Tape Out, but then I get no audio with some talkgroups, but I can hear it come through the scanner speaker when I unplug the audio cable. What has happened?
- In your programming you need to check to see if your channels are marked for "Tape Out", if not Check the correct box and rewrite programming.
Im hearing no activity on a trunked system
- Is the System configured as the correct "System Type", eg Type II or P25?
- If it's a Motorola Type I or Type II 800 MHz system is the Band Plan set to Custom. See Rebanding article for more details.
- Are the correct Control Channels frequencies programmed, are the System, Site or Frequencies not L/O or Avoided and the Quick Key's On/Enabled
- Can the scanner "hear" one of the control channels programmed as a conventional frequency? or even a nearby NOAA weather frequency?
- Is the scanner in ID Scan mode and are any talkgroups programmed? (Alternately, switch to ID Search mode.)
- Are the appropriate Groups/Departments enabled and unlocked with the id's of the talkgroups you want to listen to?
- Do you have at least one Groups/Departments Quick Key enabled and allocated for the group where your entered talkgroups are?
- Is the System offline or has a new System come online in the past couple of days, replacing the old one?
Some users are more loud than others.
- Make sure you are using the correct MODE for your FM systems. For many systems, FM (which assumes 5 kHz deviation) is the correct mode. NFM (narrowband FM, assuming 2.5 kHz deviation) is only for narrowband stations and will make those channels the same loudness as the others. AUTO defaults to NFM and was not the correct setting for most conventional systems on the air in 2010. By Today, however all systems in the US will have converted to narrowband so NFM will increasingly be the correct setting.
- You may need to adjust the digital and/or analog AGC settings like in the BCD396T
- If your model has "Volume Channel Offset" you could use positive numbers with conventional systems or digital systems you could use negative numbers or both for combined difference of almost 20db.
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