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"T" or "D"

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#1
What is the difference between "T" (TDMA) and "D" (Digital) as shown in the database. I have a GRE PSR 800 and live in Tennessee. The scanner picks up THP just fine, which is shown in the database as "D". However, it has not been receiving the TDOT HELP trucks, which are shown in the database as "T" which stands for TDMA. According to all I've read, this scanner is TDMA Phase 1 and Phase 2 capable. When the scanner tries to receive the TDOT HELP trucks, it flashes and only displays a "VC" and no voice. Thus, my question, what's the difference?
 

troymail

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#2
"D" simply means the talkgroup is digital and most any modern trunking scanner (other than those low end models which are analog only) will receive.

"T" means that the talkgroup is "capable" (probably better stated as "likely") of being in TDMA mode which requires specifically that your scanner must be TDMA/Phase 2 capable.

If the scanner is not a TDMA scanner, the radio shouldn't even stop on that talkgroup if/when that talkgroup is in TDMA mode (TDMA talkgroups can sometimes "revert" temporarily to FDMA/Phase 1 or "D" mode).

If the radio is stopping on the talkgroup but you aren't hearing anything, the user may not actually be talking and/or the radio is probably experiencing well known "digital simulcast" (LSM) issues. If it's a Uniden radio and the radio briefly stops but then quickly scans again and/or it's a Whistler radio and you hear a "busy signal" or other "digital noise" from either, it could be an encrypted channel/transmission.

In general, both Uniden and Whistler/GRE radios provide indicators on the display if the talkgroup currently being received is in Phase 1 or Phase 2 mode (DG vs. D2, P25 vs. PT0/PT1, etc.).
 
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milf

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#4
The GRE PSR 800 recieves TDMA out of the box. But yes make sure your settings are right, and DSP and CPU are updated with the last update that was available.
 

troymail

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#5
Just thought of another possibility -- trunking tables....

http://forums.radioreference.com/ge...unking-tables-needed-p25-trunked-systems.html

If you're importing from the library things should be fine. In most cases, the trunking tables for P25 systems would start out as "Auto Fill". But I've seen some situations where this isn't set properly and/or the system requires special settings.

Best thing is to check with others in your area who are/can receive the same system - ask them to share their experiences.
 

ka3jjz

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#6
The GRE PSR 800 recieves TDMA out of the box. But yes make sure your settings are right, and DSP and CPU are updated with the last update that was available.
Probably true for the last versions before GRE folded their tent, but the 800 was out well before the first X2 systems ever got discovered, and it's like that TDMA wasn't even on their horizon at the time, so it wouldn't have it in the earlier versions. As was mentioned, there was a firmware fix that you would likely need to apply if you don't have the latest and greatest.

Since their website for scanners is all but gone, your next best bet for finding the last CPU and Firmware updates would be the 800's Yahoo group, or if someone stored this in a dropbox somewhere

Mike
 
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#8
Thanks for all the replies. Just wondering - when I program the Trunked System Talkgroups, under the DMode, does it matter if it is programmed as Digital or Auto. Also, on my GRE PSR 800, how do you change the mode from Digital or Auto, and vice-versa?
 

troymail

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#9
Thanks for all the replies. Just wondering - when I program the Trunked System Talkgroups, under the DMode, does it matter if it is programmed as Digital or Auto. Also, on my GRE PSR 800, how do you change the mode from Digital or Auto, and vice-versa?
If the system is pure digital (P25, DMR, etc.) this setting per talkgroup doesn't matter since the system is digital. It could make a very slight different on a Motorola system that is mixed mode (analog and digital) but in most cases not to the point where it would/should be noticeable.

In most cases, it's probably better to set what is known (analog vs. digital), color codes (for DMR) etc. rather than letting the radio decide but there are other factors to consider when doing so.
 

troymail

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#11
Can you manually change the mode from digital to auto and vice versa?
Uncertainly exactly the question but in your programming you can manually set talkgroups to Auto, Analog or Digital on systems that can be mixed mode (i.e. older Motorola trunked systems). However, P25 and DMR can only be set to Auto or Digital (if I am not mistaken).

For the Motorola systems, if you set a digital talkgroup to analog, you'll just hear digital noise. If you set a analog talkgroup to digital, you probably won't hear anything.
 
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#12
Uncertainly exactly the question but in your programming you can manually set talkgroups to Auto, Analog or Digital on systems that can be mixed mode (i.e. older Motorola trunked systems). However, P25 and DMR can only be set to Auto or Digital (if I am not mistaken).

For the Motorola systems, if you set a digital talkgroup to analog, you'll just hear digital noise. If you set a analog talkgroup to digital, you probably won't hear anything.
I have a PSR GRE 800 and use the EZ Scan software. I haven't been able to get it to change between Auto and Digital by clicking in the "Mode" column. That was my question--how/can this be done?
 

troymail

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#13
I have a PSR GRE 800 and use the EZ Scan software. I haven't been able to get it to change between Auto and Digital by clicking in the "Mode" column. That was my question--how/can this be done?
We started out (entry #1 of this thread) talking about Project 25 (P25) systems.

If you're trying to change the "DMode" (not Mode) for a P25 system talkgroup, you can't -- P25 systems are Digital (so I have now conformed that I wasn't 100% correct in my last post about being able to set them to "Auto").
 

wa8pyr

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#14
"D" simply means the talkgroup is digital and most any modern trunking scanner (other than those low end models which are analog only) will receive.

"T" means that the talkgroup is "capable" (probably better stated as "likely") of being in TDMA mode which requires specifically that your scanner must be TDMA/Phase 2 capable.
The T actually means that a talkgroup has been confirmed to be TDMA mode, not just capable of it.

Otherwise, all is correct; the scanner must be capable of receiving TDMA, which the PSR800 is capable of but only with the last firmware and DSP updates that were rolled out for that model.

Since some talkgroups can be TDMA, and automatically revert back to FDMA when a Phase I-only radio is present, the Auto mode is best if the scanner has it.
 

troymail

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#15
The T actually means that a talkgroup has been confirmed to be TDMA mode, not just capable of it.
A couple of problems with this statement:

1. If you hover over the Mode heading on the column, the tooltip says otherwise: "T = TDMA Capable Talkgroup"

2. In some systems, talkgroups are dynamic and can be in TDMA (Phase 2) at one moment and FDMA (Phase 1) at other times - which is known as dynamic dual mode (DDM) -- it all depends on what subscriber radios are actively on that talkgroup (i.e. if a non-TDMA radio switches to and is allowed to affiliate with the with that system/talkgroup, the talkgroup ill revert to FDMA/Phase 1 as long as they are on the talkgroup - even just listening).

On a related note -- "E" (for encrypted) exposes similar characteristics -- some talkgroups are full time encrypted and others are part time/some times encrypted. The "E" can be misleading making you think the talkgroup is always encrypted.

Of course, all of this is subject to whatever the submitter of the information provided. For example, TDMA (Phase 2) is listed as "T" if the submitter provides that info (or if the system is known to be 100% TDMA) but I suspect the default is "D" since TDMA is still digital.

And, although many systems are listed as "TDMA" or "Phase 2", they can be operating entirely in Phase 1 mode. I know of several systems that are listed here as "Phase 2" but in fact are operating as "Phase 1". Some of this comes from vendor announcements or propaganda stating they are deploying a "Phase 2 compliant" system which means that at some point (could be day 1 - could be never), all of the subscriber radios on the system will become "Phase 2" and then the system will really be "Phase 2"... or, because of easing of the rules, may never become Phase 2......

Since some talkgroups can be TDMA, and automatically revert back to FDMA when a Phase I-only radio is present, the Auto mode is best if the scanner has it.
Also - Phase 1 or Phase 2 - if doesn't matter - they are both digital. "Auto" is this case really doesn't (shouldn't) matter. If the "system" is pure digital (vs. and legacy mixed-mode P16 system), the system itself will (or should) cause the talkgroups to be processed as digital anyway.
 
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