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» Knowledgebase » PSR-500/600 Why do I Notice a delay in Unmuting on certain Analog Talkgroups and Channels?
 PSR-500/600 Why do I Notice a delay in Unmuting on certain Analog Talkgroups and Channels?
Under certain conditions you may notice that the PSR-500 and PSR-600 exhibit a noticeable delay between the time the radio stops on active analog talkgroup objects (TGRPs) or analog conventional channel objects (CONVs). 

This is by design, and will occur under the following conditions:

  • The radio is searching (SVRC, LMIT or SWPR) or tuning (TUNE mode) and stops on an analog transmission
  • The radio is scanning, and stops on an active CONV object that is configured for "Sq Mode: Search" or "Sq Mode: None"
  • The radio is scanning, and stops on an active analog TGRP on a Motorola analog or mixed analog/digital system

In the above cases, the radio is designed to wait for a short period of time to determine if the active signal is analog or digital, with priority given to digital, so that you will not hear raw, undecoded digital modulation play through the radio's speaker at the beginning of a transmission (commonly known as "machine gunning"). If the active signal is digital, the radio remains in digital mode, and plays the decoded digital audio through the radio's speaker. If the active signal is analog, the radio's speaker will unmute in analog FM mode after waiting for this short period of time.

By default, the period of time that the radio waits for a digital signal is 600 milliseconds, or 6/10ths of a second. In most cases this should not result in the loss of any voice information at the beginning of an analog transmission, and should provide ample time for the radio to make the analog-or-digital determination without causing raw undecoded digital modulation to play through the radio's speaker. However, in some cases, the 600 millisecond delay may result in the loss of the very first part of an analog voice transmission, resulting in a lost syllable at the beginning of a transmission. Also, if an incoming digital signal is noisy or if interference is present, the radio may not be able to make the analog-or-digital determination within the 600 millisecond period. In these cases, a bit of raw undecoded digital modulation may be heard before the radio is able to recognize that a digital signal is present and make the switch to digital mode. 

For most users, the default 600 millisecond delay should work fine. If you find that 600 milliseconds is objectionable, there are some steps you can take to mitigate its effects on reception of analog signals. 

  • For CONV objects, the timer is disabled when the CONV object is configured to use Sq Mode: CTCSS and Sq Mode: DCS. This is true regardless of whether CTCSS or DCS are configured for a specific CTCSS or DCS code, or configured for "Search". If the CONV transmitter you are monitoring is using CTCSS or DCS, we recommend that you program the radio to use Sq Mode: CTCSS or DCS as appropriate, and set the actual CTCSS or DCS code in the object's settings. If the CONV transmitter you are monitoring does not use CTCSS or DCS, you can eliminate the 600 millisecond delay by using Sq Mode: CTCSS or DCS and "Search" as the CTCSS or DCS code. This will allow any transmission to pass without the 600 millisecond delay. Note that digital transmissions that are present on a CONV frequency set for Sq Mode: CTCSS, Search or Sq Mode: DCS, Search will be passed as raw undecoded digital modulation.
  • It is possible to change the value of the 600 millisecond timer to reduce the amount of delay that occurs at the beginning of transmissions when searching, tuning, or monitoring analog Motorola TGRPs on an analog or mixed analog/digital Motorola systems. We caution that reducing the amount of time that the radio waits to make the analog-or-digital determination may increase the instances of raw, undecoded digital signal that is heard at the beginning of digital transmissions, particularly in areas where the digital signal is weak or affected by interference. However, in some cases it may be possible to lower this value dramatically, reducing the amount of delay that affects analog reception without affecting digital reception. To change the value of this timer, follow these steps:

  1. Press PGM, then FUNC, then the GLOB softkey to access the Special Global Settings Menu. (NOTE: The Special Global Settings menu (FUNC GLOB) includes parameter settings that, if not set properly, may adversely affect the performance of your radio. We recommend that users not change the settings found in the FUNC GLOB menu unless instructed to in this manual or directed to do so by GRE Technical Support personnel. Should you experience difficulties after changing any of the settings in the FUNC GLOB menu, you can also restore those settings to factory defaults by pressing the Dflt softkey associated with each menu line, or following the 0,2 global settings reset procedure described above.)
  2. Scroll down to the "DG Int Prime" parameter. By default, DG Int Prime is configured for 60, or 60/100ths of a second. 
  3. Change DG Int Prime to a new value. We recommend a setting of at least 20 (20/100ths of a second, or 200 milliseconds) for DG Int Prime if you are scanning any type of digital conventional or trunked systems. Save the new DG Int Prime setting, then save the changes to the Special Global Settings menu
  4. Experiment with and optimize DG Int Prime by listening to digital conventional and trunked radio system traffic. If you hear too many instances of raw undecoded digital modulation at the beginning of digital transmissions, increase the value of DG Int Prime in increments of 10 until you no longer hear raw digital modulation. 

Article Details
Article ID: 10
Created On: 07 Nov 2007 06:46 PM

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