FTO-Use what Audacity says???

[timkilbride]

I have been recording fire tone outs. Should I use the value Audacity gives or pair the hz up with the industry standard? Audacity reading are 7-8hz higher then the industry standard. Just curious what everyone else does?

TIA,
Tim

[DaveIN]

I started with the industry standard tones before the XT radios came out with the tone search feature. Now I just use the as-found frequencies in the XT search function, because the XT's and older models are able to alert on them.

If you want to publish them on Radioreference or some other database, I would use the industry standards.

Also keep in mind that the Tone Out feature works better in the "FM" mode setting when searching for tones and setting up for the alert on the agency your monitoring.

[Chauffeur6]

What version of Audacity are you using to analyze the recordings?

[pdfdems286]

if you are a purist,then it may matter. for just throwing the found tone's in the scanner for tone out's, it's not all that critical. if you are setting up pager's based on the tone out information, you may want to use the industry standard.i found that trying to match the tone out's up to the table's <chart's> was a big pita.

[timkilbride]

Originally Posted by res6cue_dot_com

What version of Audacity are you using to analyze the recordings?

I'm using the latest version(not the beta) of Audacity. I updated the program before doing any recording. However, I think I did my recordings in NFM, rather then FM. I should go in and change everything to FM for a more accurate reading.

Tim

[Chauffeur6]

Using Audacity 1.2.6, here's how to get the most accurate results:

- Record in FM mode and avoid using file compression if possible to get the cleanest recordings

- Select the entire recording in Audacity, then use Effect > High Pass Filter set at 270 Hz cutoff frequency to get rid of the PL and any electrical hum

- Select as much of the individual tone as possible, then Analyze > Plot Spectrum using the following parameters: Spectrum, Rectangular Window, 4096, Log Frequency. Hover the mouse pointer over the highest peak and use the Peak: reading to determine the Hz of the tone

You should notice much more accurate results using these steps. A Hz off here or there is no big deal, but when you start getting 7 or 8 Hz off, that's going to be a problem, especially with lower frequency tones that have less deviation tolerance with decoders. It never hurts to compare your list to the actual tone plans to get the best results.

[timkilbride]

Originally Posted by res6cue_dot_com

Using Audacity 1.2.6, here's how to get the most accurate results:

- Record in FM mode and avoid using file compression if possible to get the cleanest recordings

- Select the entire recording in Audacity, then use Effect > High Pass Filter set at 270 Hz cutoff frequency to get rid of the PL and any electrical hum

- Select as much of the individual tone as possible, then Analyze > Plot Spectrum using the following parameters: Spectrum, Rectangular Window, 4096, Log Frequency. Hover the mouse pointer over the highest peak and use the Peak: reading to determine the Hz of the tone

You should notice much more accurate results using these steps. A Hz off here or there is no big deal, but when you start getting 7 or 8 Hz off, that's going to be a problem, especially with lower frequency tones that have less deviation tolerance with decoders. It never hurts to compare your list to the actual tone plans to get the best results.

I did all the above listed. For the heck of it, I used a FRS radio and the PL tone the radio generates to see how close everything was. I used PL tones 67, 114.8, 186.2, and 250.3. My results were 64hz, 109hz, 177hz, and 235hz using audacity. Seems something is still wrong here? I am using a 996t and running a mono cable from the REC jack on the scanner to the sound input on my laptop. Am I doing something wrong?

Tim

[Chauffeur6]

It's certainly possible that your laptop's audio chip is distorting the audio in some fashion. Are there separate Line In and Mic jacks, or just a single audio input jack? Using the Mic jack should be avoided, as it generally adds gain to the input which could certainly contribute to some distortion.

Looking at the difference in PL, it seems to increase exponentially as the Hz increases. That's not good, and will certainly hurt the accuracy of your results to the point that you might misidentify tones by a wide enough margin that they won't work with FTO feature.

[timkilbride]

Originally Posted by res6cue_dot_com

It's certainly possible that your laptop's audio chip is distorting the audio in some fashion. Are there separate Line In and Mic jacks, or just a single audio input jack? Using the Mic jack should be avoided, as it generally adds gain to the input which could certainly contribute to some distortion.

Looking at the difference in PL, it seems to increase exponentially as the Hz increases. That's not good, and will certainly hurt the accuracy of your results to the point that you might misidentify tones by a wide enough margin that they won't work with FTO feature.

I have just the one jack, a mic jack.

Tim

[Chauffeur6]

That could be the problem then. Using Windows? If so, take a look at the sound/audio properties and see if there's a way to disable any type of Mic Boost or gain feature on that Mic port. That might help.

[timkilbride]

I have everything disabled that might boost the audio. Will run the recorder for a while and do some checks and see what happens.

Tim

[Chauffeur6]

Good luck! If you're still not having much luck, you could take a look at a cheap USB solution like this

Newegg.com - SYBA SD-CM-UAUD USB Stereo Audio Adapter - Adapters & Gender Changers

[bctrl1]

The main problem is that there isn't sufficient resolution available with 4096 points and a 44100Hz sample rate to accurately determine the standard tones. With 4096 points you will have a resolution of about 11Hz. You can improve things a bit by increasing the analysis window to 16384 points, but you'll be even better off also dropping the sample rate to 8000Hz which will get you to sub 1Hz resolution bandwidth.

Also, the window selection might make it more difficult to accurately determine the frequency. Hanning and Hamming windows spread the tone power across frequency, making it more difficult to determine the peak. The rectangular window might be the best for this situation, but it doesn't help any if you are trying to find a low level tone.

[timkilbride]

Originally Posted by res6cue_dot_com

Good luck! If you're still not having much luck, you could take a look at a cheap USB solution like this

Newegg.com - SYBA SD-CM-UAUD USB Stereo Audio Adapter - Adapters & Gender Changers

Isn't that basically the same thing as what my computer has? MIC IN and HEADPHONES OUT?

Tim

[UPMan]

Back to the very first post...if the count is only 7 or 8 Hz off of the standard, that can be explained by either count error (the path you are taking) or transmitter drift. IOW, the transmit tone could actually be off by 7 or 8 Hz (and it would affect nothing...the receiver will still "see" it as the correct tone at that resolution).