LTR Analyzer released

[letarotor]

VHF Narrow Band Decoding Problems

I tapped a PRO-2055 today using all four components listed in the instructions because I needed a scanner that would tune to the narrow band VHF channels: ie: 153.1325, 153.5675, etc. My Uniden BC235XLT, BC230XLT and PRO-2036s wouldn't tune close enough to give good decodes. The PRO-2055 decodes UHF channels just fine, but I really have to Overdrive the signal to get a good 20% or more decode rate when one of the VHF channel becomes active, and I get no decode of the home channel blip like I normally do with a UHF home channel. Has anyone else had experience with VHF narrow band LTR systems, and is this normal? Is the discriminator audio just insufficient to drive the program on these narrow band channel systems? Should I try a different combination of resistor values? Thanks.

Mark

 

[slicerwizard]

A fitting thread for post 1000...

Anyway... My best advice is to post a .wav file recording of a few idle bursts. You can use Windows' Sound Recorder, GoldWave, etc. to make the recording. It would be very helpful if you would also include a short recording (a second or two is plenty) of clean 3600 and/or 9600 bps control channels. 22 kHz, 8 bit mono or better recordings are fine (although anything over 22 Khz, 8 bit is overkill)

With that data, I should be able to point you in the right direction.

 

[letarotor]

Eliminated 10K resistor

My sampling rate is consistent at 22195. Its doing the opposite of what the directions say. If I pull the audio level down to 80 to 90% when there is only static, I only get about 10% decode rates during a transmission and it won't decode. If I drive up the audio level to above 20% during a transmission it decodes fine, but displays Overmodulated during the static. After more monitoring, think I'm dealing with weak systems. I took the 10k resistor out before the tant and it seemed to help. I'm getting about 22% decode rate on a narrow band VHF channel, but 31% or better on a UHF channel with the same audio setting.

Another question, can a multiple channel LTR system be set up to only make one channel free in a system? I have been decoding a system that I believe has at least four or five frequencies, but LTR Analyze only shows LCN 1 as free while decoding several of the frequencies. For instance, a security company that has their Channel 1 on home channel 17, and Channel 2 on home channel 5. Both frequencies in LTR Analyzer show only LCN 1 as free. What I believe to be LCN 9 in the system also only shows LCN 1 as free.

 

[slicerwizard]

My sampling rate is consistent at 22195.

Hm. That's a 1% frequency error. The program should handle that. IIRC, it currently handles +/- 2.5%.

Its doing the opposite of what the directions say. If I pull the audio level down to 80 to 90% when there is only static, I only get about 10% decode rates during a transmission and it won't decode. If I drive up the audio level to above 20% during a transmission it decodes fine, but displays Overmodulated during the static.

Your main objective is to avoid the overdriven message during comms. When the audio is clipped, the program can't filter out the voice traffic to get at the low speed data. The 50% to 90% range recommnded by the manual represents my results with my local systems; if you're monitoring a system that has the (low speed data) audio deviation set fairly low, you may need to crank the gain up.

After more monitoring, think I'm dealing with weak systems. I took the 10k resistor out before the tant and it seemed to help. I'm getting about 22% decode rate on a narrow band VHF channel, but 31% or better on a UHF channel with the same audio setting.

Removing the isolation resistor in the scanner isn't recommended - if there is too much series resistance, lower the value of R2 at the PC end of the cable.

BTW, how are you calculating decode rates? The program doesn't display that.

Another question, can a multiple channel LTR system be set up to only make one channel free in a system? I have been decoding a system that I believe has at least four or five frequencies, but LTR Analyze only shows LCN 1 as free while decoding several of the frequencies. For instance, a security company that has their Channel 1 on home channel 17, and Channel 2 on home channel 5. Both frequencies in LTR Analyzer show only LCN 1 as free. What I believe to be LCN 9 in the system also only shows LCN 1 as free.

Interesting. What do they show when LCN 1 is in use?

 

[letarotor]

Thanks for the tips Slicerwizard.

I tried initially lowering the value of R2 and it didn't work. I've been doing this long enough to know not to take out the Tant.

The decode rate I'm referring to is what shows when there is an actual transmission. If I drive the audio up during a transmission above the 20% decode rate it begins decoding. The program will not decode the 10-second blips on this system no matter what. Not true with UHF systems in my area. On UHF systems, I can set the audio level during static at around 80% and it decodes the blips and transmissions just fine, however, with this narrow band VHF system I get nothing.

After more monitoring, I've noticed that if the home channel LCN switches traffic to the free channel LCN #1 and traffic pops up on LCN#1, that channel will show another channel free in the system, and it will alternate, but not show more than one free channel in the system at any given time. See below:

LCN#17

2/21/2008 22:59:36 + OSW: 0 17 17 072 01 4A COMM ID=17-72 on Ch17 FREE=1 LCN=17
2/21/2008 22:59:38 + OSW: 0 17 17 072 01 4A COMM ID=17-72 on Ch17 FREE=1 LCN=17
2/21/2008 22:59:38 + OSW: 0 17 17 072 01 4A COMM ID=17-72 on Ch17 FREE=1 LCN=17

LCNs seen: 01 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 17 -- -- --
Monitored: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- 17 -- -- --
Groups seen: 17-095 17-097 17-104 17-220


LCN#1

2/22/2008 16:53:26 + OSW: 0 01 09 054 05 40 COMM ID=9-54 on Ch01 FREE=5
2/22/2008 16:53:26 + OSW: 0 01 09 054 13 59 COMM ID=9-54 on Ch01 FREE=13
2/22/2008 16:53:27 + OSW: 0 01 09 054 13 59 COMM ID=9-54 on Ch01 FREE=13
2/22/2008 16:53:27 + OSW: 0 01 09 054 13 59 COMM ID=9-54 on Ch01 FREE=13
2/22/2008 16:53:29 + OSW: 0 31 09 054 01 3A END ID=9-54 LCN=1
2/22/2008 16:53:29 + OSW: 0 31 09 054 01 3A END ID=9-54 LCN=1
2/22/2008 16:53:31 + OSW: 0 01 09 054 09 54 COMM ID=9-54 on Ch01 FREE=9
2/22/2008 16:53:31 + OSW: 0 01 09 054 09 54 COMM ID=9-54 on Ch01 FREE=9
2/22/2008 16:53:32 + OSW: 0 01 09 054 09 54 COMM ID=9-54 on Ch01 FREE=9
2/22/2008 16:53:32 + OSW: 0 01 09 054 09 54 COMM ID=9-54 on Ch01 FREE=9
2/22/2008 16:53:32 + OSW: 0 01 09 054 05 40 COMM ID=9-54 on Ch01 FREE=5
2/22/2008 16:53:33 + OSW: 0 01 09 054 05 40 COMM ID=9-54 on Ch01 FREE=5
2/22/2008 16:53:34 + OSW: 0 31 09 054 01 3A END ID=9-54

LCNs seen: 01 -- 03 -- 05 06 07 08 09 -- -- 12 13 -- -- -- 17 18 19 --
Hit counts: 1 1 1 1 1 1 1

Monitored: 01 -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
Groups seen: 01-065 05-010 05-034 05-097 05-125 05-137 07-243 09-054 09-064 09-065 09-117 09-125 17-072 17-097 17-120 17-147 17-220 18-002 19-034

Scrolling doesn't work importing above, but essentially LCNs seen were 01, 05, 09, 13 and 17, the rest were erroneros. The system carrys several security companies (who use the system mostly at night) with a smattering of wrecker and delivery companies that use it mostly during the day.

 

[slicerwizard]

I tried initially lowering the value of R2 and it didn't work.

But R1 and R2 are in series, so there should be no difference?

The decode rate I'm referring to is what shows when there is an actual transmission.

The program doesn't display any decoding rates, only audio levels.

The program will not decode the 10-second blips on this system no matter what.

If you post an audio sample, I'd be able to determine why (and possibly fix it)

After more monitoring, I've noticed that if the home channel LCN switches traffic to the free channel LCN #1 and traffic pops up on LCN#1, that channel will show another channel free in the system, and it will alternate, but not show more than one free channel in the system at any given time.

The system may be set up to support PL/DPL traffic on some of those channels; That would explain why LTR traffic is steered away from them.

 

[CrazyCalifornian]

Hi Andy,

I've been monitoring sites to determine if they are LTR Standard or Passport.
On this one site I received these codes:
3/21/2008 4:06:50 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:06:50 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:08:42 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:08:43 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:08:43 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:08:45 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:21:00 - OSW: 1 21 21 078 01 00 Area=1 Invalid or unknown function
3/21/2008 4:21:06 - OSW: 1 29 26 176 00 29 Invalid or unknown function
3/21/2008 4:22:59 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:00 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:00 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:01 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:01 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:01 + OSW: 1 23 08 002 14 33 Invalid or unknown function

After Group 8-1 is finished, would the above 6 lines indicate that Group 8-2 has a call waiting on Channel 14? or what do you think?

Jay

 

[slicerwizard]

3/21/2008 4:08:42 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:08:43 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:08:43 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15
3/21/2008 4:08:45 + OSW: 0 07 08 001 15 73 COMM ID=8-1 on Ch07 FREE=15

That decoding is very poor. There should be 7.5 OSWs per second, but you only have four in 2 to 3 seconds. Either your setup is messed up or that's not LTR that you're monitoring. As always, an audio sample would provide loads of info...

3/21/2008 4:21:00 - OSW: 1 21 21 078 01 00 Area=1 Invalid or unknown function
3/21/2008 4:21:06 - OSW: 1 29 26 176 00 29 Invalid or unknown function
3/21/2008 4:22:59 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:00 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:00 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:01 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:01 + OSW: 1 23 08 002 14 33 Invalid or unknown function
3/21/2008 4:23:01 + OSW: 1 23 08 002 14 33 Invalid or unknown function

After Group 8-1 is finished, would the above 6 lines indicate that Group 8-2 has a call waiting on Channel 14? or what do you think?

If this is LTR, it is some sort of extended function.

 

[CrazyCalifornian]

After looking at the signal with a scope, it appears it might be a passport site.
It has the normal LTR Sync bits and enough bits for a passport frame.
I'll keep that in mind before I have another question about the data

 

[Eric61]

Let' s say I am scanning several frequencies believed to be part of the same LTR system. If I am seeing Comm activity from one frequency with free channel listings of 1, 3, 7, and 13 and other Comm activity from a different frequency with free channel listings of 1, 2, 3, 8, and 12, as long as traffic on the system is extremely slow is it safe to assume I am hearing activity on 2 different systems? On a long transmission, does the OSW always list all of the free channels in the system?

Thanks,

Eric

 

[slicerwizard]

Let' s say I am scanning several frequencies believed to be part of the same LTR system. If I am seeing Comm activity from one frequency with free channel listings of 1, 3, 7, and 13 and other Comm activity from a different frequency with free channel listings of 1, 2, 3, 8, and 12, as long as traffic on the system is extremely slow is it safe to assume I am hearing activity on 2 different systems?

Yes, I'd say that's two systems. As you continue to monitor, you'll see that no more LCN's show up.

On a long transmission, does the OSW always list all of the free channels in the system?

A long transmission is not guaranteed to list all system LCNs, as there can be even longer transmissions taking place on other channels (which would keep their LCNs out of the fee field on the channel you're watching)

To be sure you've seen them all, you've got to monitor for a while. Busy home channels will quickly fill out the LCN list, while a quiet non-home channel will take a long time to get the job done.

 

[Eric61]

That's what I thought- thanks.

Eric

 

[madmantravis]

need LTR Codes

I need the scaner codes for Rogers Co. Okla. City of Claremore for LTR.

 

[Jay911]

I need the scaner codes for Rogers Co. Okla. City of Claremore for LTR.

Here on this site, we have a great database which contains all this information. You can find that information there, instead of posting a message in a discussion about a completely different thing - with all due respect.

You can click on the "Database" link near the middle of the top of your browser window and navigate to Oklahoma, then to Rogers County, and then you will find the LTR system you requested info for.

I have the link here so you can get to the info directly, and save the navigation for next time: http://www.radioreference.com/apps/db/?sid=4040

Click that to get to your desired system information.

 

[slicerwizard]

I had to make some changes to the program in order to get satisfactory decoding on my new Inspiron 1720 laptop, so this update might also help those who had unsatisfactory results with previous versions.


Also:

- fixed bug that caused problems if program name or path has embedded spaces

- added audio gain control for low discriminator audio

- greatly reduced false decoding

- improved idle burst decoding

- detailed statistics reporting

- CPU usage halved


Update is in the usual location: http://home.ica.net/~phoenix/wap/LTR/

 

[Airdorn]

Hey, nicely done.

Been using it this morning, seems to work great.

 

[mbstone99]

LTR Analyzer

I had to make some changes to the program in order to get satisfactory decoding on my new Inspiron 1720 laptop, so this update might also help those who had unsatisfactory results with previous versions.


Also:

- fixed bug that caused problems if program name or path has embedded spaces

- added audio gain control for low discriminator audio

- greatly reduced false decoding

- improved idle burst decoding

- detailed statistics reporting

- CPU usage halved


Update is in the usual location: http://home.ica.net/~phoenix/wap/LTR/

Hi Andy,

I got a suggestion for your program that maybe you can see if this is possible to add in one of your next updates. Down here there a lot of LTR trunks and I have many times where are 2 separate LTR's on the same frequency. Usually they have different area codes when sharing a frequency. Anyways I am wondering if it's possible that you could somehow split the status reporting into 2 sections in this type of situation. Have 1 report where all the Area 0 LCN's are reported and 1 for where all the Area 1 LCN's are reported. I am not sure if this is an easy taste but just thought I would put that out here as a suggestion. BTW great program it works like a charm none the less the way it is.

Matt

 

[slicerwizard]

I am wondering if it's possible that you could somehow split the status reporting into 2 sections in this type of situation. Have 1 report where all the Area 0 LCN's are reported and 1 for where all the Area 1 LCN's are reported.

So something like press 's' for a regular report and press 'S' for a report broken down by signal polarity and area bit? Have you tried that?

 

[mbstone99]

LTR Analyzer

So something like press 's' for a regular report and press 'S' for a report broken down by signal polarity and area bit? Have you tried that?

Doh! I didn't even realize that was what that was for. Awesome!

Matt

 

[kd5dga]

What does it mean when a inverted polarity stat is found?