Pager Tone Decoding Question

[peq387ab]

I have a question here, I have been using the CommTek Decoder and TwoTones Tones finder. I have been logging them. One thing I noticed with these systems is they is Tones Finder rounds the the flat number and sometimes the tone is off by 1-5 hz. I have attached a link of the tones sequence I have been using. Now one County I got a list for uses the GE tones for the department I am on, and the other County next to me uses the Motorola QC II tones.

My question to you is anyone else that has decoded tones with the drift of tones off, how is the best way to match these tones correctly to what they are suppose to be?

 

[peq387ab]

https://www.pghscanner.com/tones.php

This is the cart I have been working off

 

[N9JIG]

Here is a chart I made up a while back. Hope it helps!

Most scanners that have Two-Tone decoding (Unidens) and software decoders will have some error in them, and as Two-Tone equipment has pretty loose tolerances it is common for the decoded tones to be off a Hz. or two. The error tends to be a little higher on high tones, it is usually pretty relative.

 

[wgbecks]

One thing I noticed with these systems is they is Tones Finder rounds the the flat number and sometimes the tone is off by 1-5 hz.

Question: Are you decoding these tones off of an analog (FM) frequency or are you decoding them off of a P25 system?

 

[peq387ab]

I’m decoding them off VHF analog system, with a Pro 197 Scanner into a computer thru mic jac.

 

[peq387ab]

Here is a chart I made up a while back. Hope it helps!

Most scanners that have Two-Tone decoding (Unidens) and software decoders will have some error in them, and as Two-Tone equipment has pretty loose tolerances it is common for the decoded tones to be off a Hz. or two. The error tends to be a little higher on high tones, it is usually pretty relative.

Thanks for the info. I was wondering if there is some variation drift with those software on a computer or so. I think if your within 2-3 hz of that range It’s safe to make an education guess I’m assuming based upon the tone, in most cases?

 

[N9JIG]

Yes, I have used many methods of deciphering tone codes. All have some sort of discrepancy. Using the chart I could usually figure out the proper code.

One trick is that most two-tone sets select from the same type group since when they were set up decades ago the tech was less advanced and many consoles did not have the ability to select from other groups or used discrete tone encoders that were also limited to a set series of codes. These days consoles can generate any tone desired but they still tend to stay within the group.

Uniden scanners are pretty good in Tone Search mode, usually within a Hz. or 2 at lower tones (under 1 KHz.) up to 4 or 5 at the high ones like 1800 or so.

Using tone decoding software like CommTek and others seem to be pretty similar. There was one package (of which I cannot remember which) that had a feature to display the nearest standard tone that was usually pretty accurate.

The most accurate decoding I have seen is using Audacity or Adobe Audition. I would record tone sets and run the .wav files thru the software. By clicking on the waveform it would show the frequency. I tested it against some known codes and it was usually within half a Hz. or less.

I got so good with the software that I could start to be able to tell the tone by looking at the waveform. I could even pick out the specific transmitter used by seeing the common artifacts the tone remote or console would leave on the waveform.

 

[peq387ab]

Yes, I have used many methods of deciphering tone codes. All have some sort of discrepancy. Using the chart I could usually figure out the proper code.

One trick is that most two-tone sets select from the same type group since when they were set up decades ago the tech was less advanced and many consoles did not have the ability to select from other groups or used discrete tone encoders that were also limited to a set series of codes. These days consoles can generate any tone desired but they still tend to stay within the group.

Uniden scanners are pretty good in Tone Search mode, usually within a Hz. or 2 at lower tones (under 1 KHz.) up to 4 or 5 at the high ones like 1800 or so.

Using tone decoding software like CommTek and others seem to be pretty similar. There was one package (of which I cannot remember which) that had a feature to display the nearest standard tone that was usually pretty accurate.

The most accurate decoding I have seen is using Audacity or Adobe Audition. I would record tone sets and run the .wav files thru the software. By clicking on the waveform it would show the frequency. I tested it against some known codes and it was usually within half a Hz. or less.

I got so good with the software that I could start to be able to tell the tone by looking at the waveform. I could even pick out the specific transmitter used by seeing the common artifacts the tone remote or console would leave on the waveform.

Thanks for this info. I have noticed that based upon your chart from what I have decoded over the months makes sense to the range that they are within 3 hz or less in most cases. Some I have noticed drifted a bit higher like 5 hz but they are close tho to a tone within the chart range. Its fairly easy to follow the QC II tones since like you said almost all are in that range of the reed group. One thing I did notice was one county took a mix of QC II and Plectron and then they used Tone A is a QC II and Tone B is a Plectron one, which I found interesting.

Thanks for this helpful information. My data that I have collected is now flowing easy looking at these charts and your wonderful color chat to match tones up.