Frequency Discrepancy in FTO Feature

[menace915]

Greetings forum members,

I was wondering if I could get your input on an issue I am having with my 396XT Uniden FTO feature. Please bear in mind that I am not too knowledgeable in the radio/electronics department, so forgive me in advance if my questions are too easy.

I am currently using the FTO feature in my scanner to obtain frequencies for my hospital since nobody seems to know what frequencies we use in our emergency fire pagers. We are currently using Nova Pagers under VHF 152.0075 frequency, but I have heard good things about the Minitor V and I would like to have one programmed to my tones so I can supplement my old Nova Pager.

All out pager tests are done twice a day, once at 0730, and once at 1930. Over the past few days, I have obtained the frequencies that activate the pager, but I have noted some discrepancies. Below is what I have obtained:

Trauma Activation: 350.5/410.7, 348.5/409.5, 348.6/410.5, 349.3,412.0, 349.5/410.8
Code Activation: 511.4/434.6, 510.7/433.6, 456.7/434.1, 457.7/433.7
Rapid Response: 458.5/457.9, 512.1/510.7, 510.8/433.6, 512.5, 433.3

Assuming that the system is using Motorola Quick Call, based on the chart, the only one I am pretty sure of is the trauma tones, which appear to be 349.0/410.8. As you can tell, there are major differences between the code and rapid response tones. Either the operator activated the pager under a 'code' and announced a rapid response, or the frequencies were changed.

Am I correct in assuming that these are Quick Call tones? I know there are other tones such as Plectron. Is there any way for me to know what kind of tones are used (i.e. motorola vs plectron)?

My other question is: by how many Hz can a tone frequency be off by and still make the pager alert? Should I program the tones the way my Uniden Scanner picks them up, or use the conversion from the chart?

Thank you in advance for your help.

 

[ecps92]

http://www.midians.com/pdf/tone_signaling.pdf

 

[DaveNF2G]

The FTO search feature can have a frequency error of about 4%, which could be too much for reliable activation with higher frequency tones. 4% of a bigger number is a bigger error.

 

[menace915]

So even though some of the frequencies land very close to the tone on the motorola chart, they could still be incorrect if programmed into the pager or into the scanner?

 

[Avery93]

So even though some of the frequencies land very close to the tone on the motorola chart, they could still be incorrect if programmed into the pager or into the scanner?

Technically, yes they would be incorrect, but would likely still work. As far as I can tell by looking through the programming software, the Minitor V can tolerate a frequency error of up to 1.55%, which at these frequencies is between 5 and 8 Hz. Given the relatively small amount of error in the tones you decoded, the actual tones being transmitted are almost certainly the standard Quick Call II tones; and as such, you would want to program those into a pager.

From looking at the tones you decoded, the trauma activation tones are 349.0/410.8 for sure; however you have more than one set of tones listed for the other two. Code Activation could be either 510.5/433.7 or 457.9/433.7. The rapid response tones could be a group (long) tone of 457.9 or 510.5, or it could be 510.5/433.7. You will need to actually listen to the tones over the air, in addition to using FTO search in order to figure out which set of tones are correct for your Code and rapid response pages.

 

[menace915]

Thanks for all your responses, they've been very helpful.