Tom Swisher writes: "To convert hex codes (if you have them) to TrunkTracker digital:
A couple days ago, I posted a short "tutorial" on the hex-to-decimal conversion of Motorola Type II talkgroup codes. Here is a little additional info along with an explanation ot Type I codes. Warren Whitby has already asked if he could post that article to his web page, which I told him was OK. If anyone else wants to post that previous text and this to a Trunk Tracker web page, feel free. Just give me and the AOSC credit, and show a link to the AOSC's web page, which is in my signature. This text along with the previous post will be refined by one of our column editors and used in an upcoming issue of our newsletter.
On Type II systems, there is apparently a limit of approximately 3000 Talkgroups. I don't yet know if that limit is related in any way to the number of radio frequencies used the system. There is a limit of 28 frequencies per system. Put an asterisk on that last comment. If the TRS (Trunk Radio System) has DEDICATED frequencies specifically for use as a phone patch, or for mobile data terminals, there can be more that 28 frequencies in use, but only 28 of them will be used by the TRS. As an example, if you look at a current listing for the Columbus, Ohio system, you will see (I think) 31 frequencies - 28 for the TRS and 3 for MDTs.
Moving on to Type I systems, the Motorola Subfleet codes are MUCH easier to convert to Trunk Tracker codes. A Motorola code of 100A will display as 100-1 on the Trunk Tracker. 100B will be 100-2, and so on. The first digit is the Block number, the second and third digits are the Fleet, and the last digit (or last two digits) is the Subfleet. If you can get access to the program code for a Type I system, it will only take a few minutes to figure out the entire Fleet Map. Simply go through the list and convert the letters to numbers, remembering that the first Subfleet in always ###-1 and the last is always ###-0. If you don't have access to this info, figuring out the Fleet Map of a Type I system can be more frustrating that trying to convert Type II hex codes without ANY calculator!
You can take a guess at how many users there will be for s Type I system, and carry on from there. You can probably assume that every department of the governmental agency that owns the system will have some radio access. The Police and Fire Departments will be the biggest users, which the Zoning and Building Inspections departments will probably be the smallest, and might even have only one Subfleet of a Fleet that might be shared with a few other small departments.
Here's how the Fleet Map of a Type I system works. It is (not surprisingly) very closely related to the Hard Drive/Directory/Subdirectory/File structure on a computer, with specific limitations with regard to quantity. A Type I system can be looked at as if it were a computer with multiple hard drives, which or course, are of fixed but flexible capacity. And like the partition table of a hard drive, the Fleet Map can not be changed without reprogramming the entire fleet of radios. If you want to change the number of partitions on a hard drive, you must reprogram everything because doing so requires that you reformat the drive. The Fleet Map is to the TRS what the Partition Table is to the hard drive. Let's take a detailed look.
A Type I system can be compared to a computer with eight hard drives (yeh, I know - 8 hard drives means SCSI, and that gives everyone a headache, but bare with me, hihi). Each hard drive relates to one Block in the Type I Fleet Map. The Fleets and Subfleets and Radio ID's relate the the directories, subdirectories and files of a hard drive. The difference is that once a hard drive is formatted, we can dynamically change the number of directories and subdirectories and files. Once the Type I system is programmed, the Fleet Map is pretty much cast in concrete, until the entire Block gets reprogrammed. And there is a specific limitation on the number of Fleets (directories), Subfleets (subdirectories) and IDs (files) that can be on each drive.
A Type I system uses "Size Codes" to determine the number of Fleets, Subfleets and IDs based on needs determined by the System Administrator. Now, here's where we put an asterisk on the statement that there are 8 Blocks in the TRS. If a System Administrator needs a Fleet for a very large number of IDs, such as for a big city Police Department, a Block, or number of Blocks, can be eliminated and the extra IDs given to the needy department. Compare this to taking out a "half-height" (the now standard form-factor for a hard drive) and installing a "full-height" high-capacity hard drive. The full-height drive takes up the same physical space as two normal size drives.
When the system is programmed, the number of Fleets, Subfleets and IDs must be predetermined. The Fire Department (unless it's FDNY or LAFD) will probably need 300-400 IDs, once you consider a portable for each person plus a mobile unit for each truck plus the dispatcher, etc. The Fire Department also probably wants at least 10 to 12 subfleets to allow for a few fireground channels, medics, administration, maintenance, training, etc. Give the Fire Department a Block using Size Code 4, which allows one Fleet (directory) 16 Subfleets (subdirectories) and 512 IDs (files). The Police Department probably has twice the staffing of Fire, and therefore needs a lot more IDs, but they don't need any more Subfleets than does Fire. They'll want a Dispatch Subfleet for each precinct, plus subfleets for Admin., Detectives, Car-to-car, Homicide, Drug Enforcement, etc. Let's give them Size Code 12, which takes two Blocks but still has only 16 Subfleets, but allows 1,024 IDs. Now, you've still got all the other departments left. Water/Sewer, Street Maintenance, Trash Collections, Building and Ground Maintenance, etc may only need half (or less) the number of IDs that Fire wants, and also fewer Subfleets. Use Size Code 3 (8 Fleets each having 8 Subfleets and 128 IDs per Fleet) or Size Code 9 (8 Fleets, 4 Subfleets and 256 IDs per Fleet).
The best way for the Trunk Tracker listener to determine if the Size Code is correct for each block is: 1- What Sounds like the "primary" Subfleet is coming up on first Subfleet number (ie: 403-1); 2- you are hearing both sides of the conversation on the same Subfleet, and you are seeing a mix of even and odd numbered Subfleets. If the conversation changes Subfleets once or twice when one person drops the mic key and there is a pause before the reply is made, or you are seeing only odd or even numbered Subfleets, you probably have the Size Code wrong.
To get started when you first program a Type I system, if it is a municipal system, try the E1P3 Preset Fleet Map. If it's a business system, I've heard some people have pretty good luck doing User Defined Fleet Map using Size Code 7 for all 8 blocks.
I hope this all helps. Neither Type I or Type II are easy to figure out. But if you can get a copy of the Fleet Map, your work will be much easier. For Type II systems, you'll need a scientific calculator to convert Motorola's hex codes. For a Type I system, if you can get a copy of the Fleet Map, all you have to do it a simple letter-to-number conversion. If You don't have access to any of that info, Type II systems become the easiest to figure out, and Type I becomes more difficult.
Dave writes: "Channel A should be ###-1, Channel B should be ###-2 and channel C should be ###-3. There will be al least one more available subfleet for their use, which might be ###-0. The smallest number of subfleets in a Type 1 system is 4. Try one of the size codes that has four subfleets per fleet. TT users that I know who have tried to listen to business systems have had their best luck using S7 or S8 size codes for every block in the business systems."
Converting Motorola Hexidecimal IDs to Decimal IDs
by Warren Whitby
I've seen several methods, such as using the Windows 95 scientific calculator, or programs designed to convert Hex to decimal. Here's the way I convert hex to decimal IDs for the web page. I'n Microsoft Excel, there is a function called HEX2DEC that converted hex to decimal notation. All you need to do is add a new worksheet to an existing workbook, and place your hex ids in one column (we'll use column A.) In the next column (column B), change the cell properties to make all cells in that column numbers. Then create the following formula in column B: =HEX2DEC(A1)*16 and paste it in all of the cells in column B. Voila, decimal IDs that you can use with your trunktracker. I'm using Excel 97 and I had to install this function by going to Tools -> Add Ins. Also, you may want to check the previous versions of Excel to see if this function is supported.
Trunktracker |
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Type II Block
No equivalent |
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E1P1 | S11 | S11 | S11 | S11 | S11 | S11 | S11 | S11 |
E1P2 | S4 | S4 | S4 | S4 | S4 | S4 | S4 | S4 |
E1P3 | S4 | S4 | S4 | S4 | S4 | S4 | S12 | N/A |
E1P4 | S12 | N/A | S4 | S4 | S4 | S4 | S4 | S4 |
E1P5 | S4 | S4 | S12 | S4 | S4 | S4 | S4 | S4 |
E1P6 | S3 | S10 | S4 | S4 | S12 | N/A | S12 | N/A |
E1P7 | S10 | S10 | S11 | S4 | S4 | S4 | S4 | S4 |
E1P8 | S1 | S1 | S2 | S2 | S3 | S3 | S4 | S4 |
E1P9 | S4 | S4 | S0 | S0 | S0 | S0 | S0 | S0 |
E1P10 | S0 | S0 | S0 | S0 | S0 | S0 | S4 | S4 |
E1P11 | S4 | S0 | S0 | S0 | S0 | S0 | S0 | S0 |
E1P12 | S0 | S0 | S0 | S0 | S0 | S0 | S0 | S4 |
E1P13 | S3 | S3 | S11 | S4 | S4 | S0 | S0 | S0 |
E1P14 | S4 | S3 | S10 | S4 | S4 | S4 | S12 | N/A |
E1P15 | S4 | S4 | S4 | S11 | S11 | S0 | S12 | N/A |
E1P16 | S3 | S10 | S10 | S11 | S0 | S0 | S12 | N/A |
Smartnet is the Motorola trade name for their public safety trunking. It can be set up one of two ways:
1. Simulcast, in which all transmitter sites have the same frequencies and broadcast all transmissions of all talkgroups no matter where the mobile units in question are located.
2. Smartzone, in which each transmitter site is set up as a separate trunking site with it's own control channel, and usually has frequencies totally different than the other sites. When a mobile unit set on "DISPATCH EAST", for example, enters the area of a particular transmitter site, the radio sends a transmission to that site and logs on ("affiliates") with that site. That site will then broadcast all transmissions on "DISPATCH EAST". When the mobile unit leaves the area and affiliates with another site, "DISPATCH EAST" will no longer be heard on that site. It's somewhat similar to the way a cellular telephone (shhhh!) system operates.
The only talkgroups you will hear from a Smartzone site are those that have a mobile unit set to them affiliated with the site.
EDACS systems are similar to Type I Motorola system, in that they both have fleets and subfleets. With a four character Hex ID, the first two characters are the "agency." The next character is the "fleet" and the last character is the "talkgroup" (subfleet.) For example, Hex talkgroup 0121 from the Montgomery County, Alabama Sheriff's system would translate to agency 01, fleet 2, talkgroup 1.
EDACS fleets can have 16 talkgroups, with values from 0 to 9 and a to f. Talkgroup 0 in each fleet is normally used as a simulcast group to transmit accross all talkgroups in the fleet. The agency/fleet/subfleet arrangement is configurable at initial installation by Ericsson.
Second, if the above fails, check with someone who listens to your local trunk to determine if it is a Motorola system. A good place to ask may be the local RadioShack or a friend who is a amateur radio operator or scanner buff. You can check the Police Call Plus frequency directory (at the local RadioShack). Police Call Plus now also has some trunktracker talkgroup information.
If your system is not a Motorola trunked system then the Trunktracker can only scan the frequencies in the conventional mode (with lots of beeps, buzzes and missed conversations).
If your system is indeed a Motorola trunked system, then find all the frequencies used. You can not program the mobile frequencies in the trunking mode (Only 800MHz trunked frequencies from 851.0000 to 868.9875). You should have less than 30 repeater frequencies in your system (no less than 3 frequencies will be in use in a trunked system) If you have more than 30 frequencies, then you may have two systems assigned to the same license, but used for two diffrent services. A system that big should have lots of people Trunktracking, with information just waiting for you on a web page. If not, sending an email to this list could get the information you need.
To hear all the activity on the system you will need to program all the repeater frequencies in use for that system.
If you do not have any saved frequencies in your Trunktracker, or if you have them written down, then press the 2 and 9 keys wile turning your radio on. This will clear the memory and anything that the factory may have set during testing.
Turn your radio off and back on and press the "Trunk" key until it beeps twice. The display will flash Bank 1 through 10 and Trunk. Now choose the bank you wish to program (I.E. #1 for Bank 1). If you did not get two beeps and a flashing screen then try again.
The bank number you choose will now have a bar under it, a "P" will be at the left and the corresponding channel number will show next to the frequency, which will be empty or "000.0000" until you are ready to enter a frequency.
You are now ready to enter the frequencies in your Trunked system. Using the number buttons, type the frequency in with or without the decimal. (The decimal is not needed because the radio will add it for you) After you have typed in the frequency, press "E" to enter it into the channel number to the left of the frequency. The next channel number will then show along with "000.0000" waiting for your frequency entry.
Continue entering the frequencies until you have entered your entire list. As you enter the frequencies you should hear a "buzz saw" sound of the "control channel". This frequency may change once or twice a day or it may not change at all depending on the system. You may hear more than one frequency with a "buzz-saw" sound but with a higher sounding pitch. This could be a mobile data terminal, a data signal within the trunked system, but leave it in, it could be used for voice later.
After you have entered all the frequencies, press the "SRCH" key and when activity is on the trunk, a Uniden decimal number will show on the display where you entered your frequencies, this number is called a talkgroup. Press the "DLY" key to continue hearing conversations from the same talkgroup after the monitored radios unkey within 5 seconds. A bar will show you what channel the radio is monitoring the control channel on when no activity on the trunk. When a talkgroup becomes active a bar will show up at the top showing you what frequency in the trunk is currently in use. If a bar shows up with no activity then it could be an interconnect or telephone patch. The Trunktracker will monitor the control channel until a talkgroup becomes active. The Trunktracker then switches frequencies and follows the talkgroup as it skips from channel to channel until the activity has ended then returns to the control channel to wait for the next talkgoup. Your Trunktracker only has one receiver.
If you want to see all the activity on the trunk press and hold "SRCH" until you hear two beeps. You will see all the active talkgroups (except patches or telephone interconnects), one at a time, wile they are in use, but you will not hear the activity. To return to tracking press the "SRCH" key again.
If you want to listen to only one talkgroup you can press "HOLD". When you are finished, press "SRCH" to continue tracking.
If the local dog catcher or the water department talkgroup is on all the time and you cannot hear the fire dispatch talkgroup, you can lock the talkgroup out by pressing "L/O" when the talkgroup appears.
To unlock a talkgroup press "L/O" until it beeps twice. Then using the "HOLD" key or "LIMIT" key to scroll up or down, locate the talkgroup you wish to unlock and press "L/O" again to remove it from the lockout list.
To remove all the lockouts from the list, press "L/O" until it beeps twice and then press "E" (enter).
73's and happy Trunking! Dave K9DV
1) Make sure that the system is a really a Type I, or has Type I blocks in it. You've probably already discovered that some of the IDs just don't look right, meaning that the conversations seem to jump around to multiple blocks, or the IDs aren't evenly divisible by 16 or 32. Some of the IDs end in an odd number or aren't divisible because of the way the trunktrackers handle the Motorola status bit. See the section above titled "Motorola Status Bit Special Functions" for more information.
2) OK, now you've determined that a large number of IDs are possibly Type I. Next, enter those IDs into a spreadsheet. Enter all of them, including the ones that you may have identified as a genuine Type II ID. Make one column (column A) the ID and the other column (column B) the repository of your notes about how the system is used. Then, sort the spreadsheet by column A (make sure you sort everything by A) in acending order.
3) Using the chart below, group the IDs into each block.
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4) Now that you've determined which blocks are active and of those blocks, which can be Type I, you need to figure out the size for each block. Type II IDs are easy, the only size code for Type II blocks is S0. The rest require a little more detective work on your part. Gary Hahn has a really outstanding conversion tool using a Microsoft Excel spreadsheet that has made available at his website. By plugging in the IDs you find while monitoring the system in Type II mode, it can help you narrow down a fleet map. Using Gary's spreadsheet, look for a block size that seems most logical. For instance, if you have six seperate users in one block, you are going to need six seperate subfleets.
5) After determining what you suspect the fleet map is, program it into your trunktracker and monitor. You are probably going to have to revise block sizes based upon your monitoring.
There is one other method that may work in some cases. Ask the user of the system, or the radio shop that supports the system, for a fleet map using Motorola size codes. Some may give it to you, some may not. Then convert those Motorola size codes into trunktracker format with the table in the section titled "Converting Motorola Type I Size Codes to their Trunktracker Equivalent." Good luck and happy monitoring.
Determining Base and Offset Frequencies for the BC245xlt
by John C.
From the data I received it seems that you need to know JUST any TWO output frequencies of the 400 MHz trunked system you are after PLUS their HEX channel numbers decoded by Trunker (see below for a list of Frequencies and their Hex and Decimal equivelents - WW.)
If frequency 1 = F1 (in MHz) and it's channel number = DEC1 (in decimal,
converting from HEX1) and similarly you have F2 and DEC2, then
OFFSET (in kHz)= 1000* ((F1-F2)/(DEC1-DEC2))
If you then convert OFFSET to MHz (divide by 1000 of course)
BASE = F1-(( DEC1-380 )*OFFSET(in MHz)) or
BASE = F2-(( DEC2-380 )*OFFSET (in MHz)) which should give you the same answer.
I checked using the Wright-Patterson Air Force Base system trunker
data I received. For WPAFB, knowing output frequencies F1 =
406.55 and HEX1 = 180 so DEC1 = 384 (convert from 180hex)
and F2 = 407.35 and HEX2 = 190 so DEC2 =
400 (I just picked any two freqs)
OFFSET = 1000x ((406.55-407.35)/(384-400)) = 50kHzUHF Frequencies and their Hex and Decimal Channel Numbers
and
BASE = 406.55-((384-380) x 0.050) = 406.35MHz
Frequency Hex Decimal
Frequency Hex Decimal 406.0000 17C 380406.0250 17D 381406.0500 17E 382406.0750 17F 383406.1000 180 384406.1250 181 385406.1500 182 386406.1750 183 387406.2000 184 388406.2250 185 389406.2500 186 390406.2750 187 391406.3000 188 392406.3250 189 393406.3500 18A 394406.3750 18B 395406.4000 18C 396406.4250 18D 397406.4500 18E 398406.4750 18F 399406.5000 190 400406.5250 191 401406.5500 192 402406.5750 193 403406.6000 194 404406.6250 195 405406.6500 196 406406.6750 197 407406.7000 198 408406.7250 199 409406.7500 19A 410406.7750 19B 411406.8000 19C 412406.8250 19D 413406.8500 19E 414406.8750 19F 415406.9000 1A0 416406.9250 1A1 417406.9500 1A2 418406.9750 1A3 419407.0000 1A4 420407.0250 1A5 421407.0500 1A6 422407.0750 1A7 423407.1000 1A8 424407.1250 1A9 425407.1500 1AA 426407.1750 1AB 427407.2000 1AC 428407.2250 1AD 429407.2500 1AE 430407.2750 1AF 431407.3000 1B0 432407.3250 1B1 433407.3500 1B2 434407.3750 1B3 435407.4000 1B4 436407.4250 1B5 437407.4500 1B6 438407.4750 1B7 439407.5000 1B8 440407.5250 1B9 441407.5500 1BA 442407.5750 1BB 443407.6000 1BC 444407.6250 1BD 445407.6500 1BE 446407.6750 1BF 447407.7000 1C0 448407.7250 1C1 449407.7500 1C2 450407.7750 1C3 451407.8000 1C4 452407.8250 1C5 453407.8500 1C6 454407.8750 1C7 455407.9000 1C8 456407.9250 1C9 457407.9500 1CA 458407.9750 1CB 459408.0000 1CC 460408.0250 1CD 461408.0500 1CE 462408.0750 1CF 463408.1000 1D0 464408.1250 1D1 465408.1500 1D2 466408.1750 1D3 467408.2000 1D4 468408.2250 1D5 469408.2500 1D6 470408.2750 1D7 471408.3000 1D8 472408.3250 1D9 473408.3500 1DA 474408.3750 1DB 475408.4000 1DC 476408.4250 1DD 477408.4500 1DE 478408.4750 1DF 479408.5000 1e0 480408.5250 1e1 481408.5500 1e2 482408.5750 1e3 483408.6000 1e4 484408.6250 1e5 485408.6500 1e6 486408.6750 1e7 487408.7000 1e8 488408.7250 1e9 489408.7500 1EA 490408.7750 1EB 491408.8000 1EC 492408.8250 1ED 493408.8500 1EE 494408.8750 1EF 495408.9000 1F0 496408.9250 1F1 497408.9500 1F2 498408.9750 1F3 499409.0000 1F4 500409.0250 1F5 501409.0500 1F6 502409.0750 1F7 503409.1000 1F8 504409.1250 1F9 505409.1500 1FA 506409.1750 1FB 507409.2000 1FC 508409.2250 1FD 509409.2500 1FE 510409.2750 1FF 511409.3000 200 512409.3250 201 513409.3500 202 514409.3750 203 515409.4000 204 516409.4250 205 517409.4500 206 518409.4750 207 519409.5000 208 520409.5250 209 521409.5500 20A 522409.5750 20B 523409.6000 20C 524409.6250 20D 525409.6500 20E 526409.6750 20F 527409.7000 210 528409.7250 211 529409.7500 212 530409.7750 213 531409.8000 214 532409.8250 215 533409.8500 216 534409.8750 217 535409.9000 218 536409.9250 219 537409.9500 21A 538409.9750 21B 539410.0000 21C 540410.0000 21C 540410.0250 21d 541410.0500 21e 542410.0750 21f 543410.1000 220 544410.1250 221 545410.1500 222 546
406.3500 ,GROUP 1 ,MOBILE 415.1500 ,GROUP 1, BASE
407.1500 ,GROUP 1, MOBILE 415.9500 ,GROUP 1, BASE
407.9500 ,GROUP 1, MOBILE 416.7500 ,GROUP 1, BASE
408.7500 ,GROUP 1, MOBILE 417.5500 ,GROUP 1, BASE
409.5500 ,GROUP 1, MOBILE 418.3500 ,GROUP 1, BASE406.7500 ,GROUP 2, MOBILE 414.7500 ,GROUP 2, BASE
407.5500 ,GROUP 2, MOBILE 415.5500 ,GROUP 2, BASE
408.3500 ,GROUP 2, MOBILE 416.3500 ,GROUP 2, BASE
409.1500 ,GROUP 2, MOBILE 417.1500 ,GROUP 2, BASE
409.9500 ,GROUP 2, MOBILE 417.9500 ,GROUP 2, BASE406.5500 ,GROUP 3, MOBILE 415.3500 ,GROUP 3, BASE
407.3500 ,GROUP 3, MOBILE 416.1500 ,GROUP 3, BASE
408.1500 ,GROUP 3, MOBILE 416.9500 ,GROUP 3, BASE
408.9500 ,GROUP 3, MOBILE 417.7500 ,GROUP 3, BASE
409.7500 ,GROUP 3, MOBILE 418.5500 ,GROUP 3, BASE406.9500 ,GROUP 4, MOBILE 414.9500 ,GROUP 4, BASE
407.7500 ,GROUP 4, MOBILE 415.7500 ,GROUP 4, BASE
408.5500 ,GROUP 4, MOBILE 416.5500 ,GROUP 4, BASE
409.3500 ,GROUP 4, MOBILE 417.3500 ,GROUP 4, BASE
410.1500 ,GROUP 4, MOBILE 418.1500 ,GROUP 4, BASE
I have been running Trunker for some while now, using a PRO-2026 - Data
Slicer combination on Com 4 for data channels and a PCR100 on Com 2 for
trunk following, now this works fine on my desktop PC with 4 Com ports,
but how do I run it all on a notebook PC with only 1 Com port?? Well, so
I have found out.. quite easily.. Take one 9 way serial cable (9 pin male
on one end and female on the other), About 12" from the male end, cut the
cable in two.. Strip both ends back about 1.5", you should find 9 coloured
wires plus a screen wire, strip all the wires back about .25", and with
a continuity tester, trace each wire to its pin... Make a note of your
findings.. Twist all the stripped wires of the same colour together and
tin them
with solder.. Find a 25 way male serial connector, and using the note
of your findings, solder the wire pairs to the corresponding pins on the
25 way male... Mine works as follows (your mileage may vary):-
9 pin 25 pin wire colour
1 8 Brown
2 3 Red
3 2 Orange
4 20 Yellow
5 7 Green
6 6 Blue
7 4 Violet
8 5 Grey
9 22 Black
Screen Shell Screen
The 9 way female connects to the notebook PC, the 9 pin male to
the PCR1000 and the 25 way male to the data slicer interface, tell Trunker
that the data slicer and scanner are on Com 1, and it all works as good
as gold together..
The radio user can either select another user from a list that has been pre-programmed or enter the other radio ID himself. Each radio is given a unique ID, and on systems with Private Call, the user is told what that ID is. So, if user "A" wants to call user "B", user "A" would enter in user "B"'s radio ID. The trunking controller will alert user "B" that he is being Private Called, at which point user "B" can acknowledge it (and the conversation becomes one-on-one) or ignore it. (Note: Motorola Systems work similarly.)
UHF or VHF patches on EDACS systems show up in the 07xx Hex range (AFS
15-140 through 15-157, 2030 through 2047 in decimal system.)
Perhaps this has been addressed already, so please forgive the repeat if it has. I may have found an undocumented feature in the 245xlt that was implemented in later versions of previous Trunk Trackers.
While Motorola Trunk Tracking on the 245xlt, pressing the SVC button causes the DATA (with the slash through it) to light on the display. I believe this changes the squelch method used by the TT to address an audio clipping problem that happens while monitoring certain Motorola trunked systems.
The problem was discovered with early versions of the first Trunk Trackers.
Greg Knox did some investigating and found the clipping was caused by wideband
noise bursts in the sub-audible portion of the voice channel. These
noise bursts occasionally cause the TT to think it's receiving the disconnect
tone and jump back to the control channel, where it sees that the conversation
is still in progress, and therefore moves back to the voice channel…and
the cycle goes on. Why this occurs is
somewhat of a mystery, but his best guess was that it is due to distortion
in the voice band spectrum getting into the sub-audible portion, possibly
caused by the transmitting equipment itself.
A fix was implemented in later versions of the 235xlt and PRO-90 by
pressing the SVC button. Now, it appears it has been carried over
into the 245xlt. But the manual says nothing about it. Pressing
SVC while tracking and EDACS does nothing, only while tracking a Motorola
system.
For those with the new 245xlts, here is a painless
way to determine LCNs. It will require use of a second 800Mhz
capable scanner. This second scanner can be any 800Mhz scanner.
The following assumes you're starting from scratch. Make sure
you have a valid list of frequencies used under the
license for that system. If its multi-site or networked, make
sure you only have those frequencies valid for the
site you're interested in. The FCC License will usually list
these.
First, put your 245xlt into Trunk Mode, and select the 'Ed' mode for
the bank you'll be using. Immediately put the
current (active) data-channel into the last channel in that 'Edacs'
Trunk Bank.
Now, start with the first channel in the Edacs bank for LCN1, put a frequency in there, then hit 'SEARCH'. Now make sure you have that same frequency keyed into the other 800Mhz scanner, and leave that scanner on that frequency. If the 245xlt doesn't mirror the same audio as the other non-trunk scanner, then zero-out LCN1, and try that same frequency in LCN2. So-on and so-on, til you find its right place ; After you find its correct LCN slot, zero-out that LCN, and move onto the next frequency, taking notes of the slot-assignments, as you progress. When you have all the slots, its time to put the data-channel in its correct slot. If you have more than one LCN that isn't figured out, wait for the data channel to switch to another LCN, then put the former data-channel frequency into one of the unknown LCN slots. Sit your non-trunk 800Mhz scanner on to that frequency, and wait for it to come alive. If both scanners mirror the same audio, you've got it.
The 245xlt does not seem to be concerned with the currently active LCN
assignment, for the Data-Channel. The above listed
method allowed me to positively identify all the LCNs for a Nextel
Edacs Business TRS.
I just tried it on a Military VHF trunked system and found that Uniden
hard limited the base reference freq to 137 Mhz on VHF. Guess what the
base freq for the system is 136 Mhz. So depending on the base freq on a
VHF system the 245 may be unable to be setup to track the system.
They easiest way to tell is a system is Multi-net is one of the repeaters will remain keyed up with what sounds like dead air (there's actually sub-audible data constantly being transmitted); it's the control channel for the system. Listening on a scanner, it will drive you nuts because of that one repeater staying up all the time.