Tones Make Reception Worse

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SCPD

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I have a Pro-97. For some frequencies, the CTCSS or DCS tones cause transmissions to cut out every few seconds. Why? Does it happen with a lot of scanners?
 

JASII

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Tones

We will need some more details here. For example, what frequencies and tones are you having problems with? If I recall correctly, some scanners can display the wrong tones on search mode and then if they are programmed in it will result in the effect that you are having. The other issue is, on very weak signals you do need a stronger signal on a channel that is being received with PL tone than carrier squelch. In fact, a digital PL signal requires an even stronger signal than the one with analog PL. I don't recall all the details right now, but that is what I remember.
 

KC5EIB

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If transmissions cut out every few seconds, the Priority function might be turned on. This will cause the scanner to jump to the channel marked as priority evert 2 seconds to check for activity. Note: If the scanner is stopped on a trunk system, the priority check will not tale place.
 

SCPD

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Trenton, GA. P.D. 155.0925. DCS 114.
Catoosa Co. GA. School Buses. 453.975. DCS 226.
Both tones are the ones listed on this site. They are not weak. Priority is not on.
 

n2mdk

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Tones really aren't need for receive if they are causing a problem turn them off. It's that simple.
 

xpawel15x

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mrrandb said:
I have a Pro-97. For some frequencies, the CTCSS or DCS tones cause transmissions to cut out every few seconds. Why? Does it happen with a lot of scanners?
I have the same problem with some frequencies on my Pro-97, I noticed this happens mostly on freqs with DCS codes programmed. The DCS code will make the frequency to pause every few seconds, very annoying! Turning it off, or putting it on DCS search gets rid of the problem.
 

Eng74

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The Pro 97/2055 DCS will not track. It has been a problem since the 97 came out. It sounds like the priority is on and drops out every 2 to 3 secounds. Even with the right DCS code programmed it will do this.
 

SCPD

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N1BHH said:
If a transmitter has over-deviation, that will cause what sounds like dropouts of a signal. The PL or DPL may be overdriven by voice peaks causing clipping of your reception.
In other words the signal is too strong?
 

n2mdk

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Not really it's the audio input into the radio causing the radio's deviation to go outside the receivers capability. Deviation is how the signal is modulated in FM if it goes out of range the audio gets clipped and cuts out. It can also drown out the code squelch heard by the radio and cause the radio not to receive. Just turn off the tone and see if it stops.
 

DonS

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mrrandb said:
In other words the signal is too strong?
Not necessarily. Certain [EDIT: possibly overmodulated] voice patterns will do it, too.

For example, one of my county Sheriff's channels uses a CTCSS tone of 179.9 Hz. When a certain female dispatcher talks, some of my radios will "mute" periodically. It's as if her voice is fooling a "reverse burst" detector, making the radio think the transmission is over - until it picks up again during the delay time. On this one frequency, I avoid the problem by putting the radio in its "CTCSS search" mode.

DCS has something similar (200 mS of 134.4 Hz, IIRC). If your radio is "fooled" into thinking it received that signal, and if it supports the DCS "turn off code", it would likely mute audio. (The PRO-97 manual doesn't explicitly say the scanner supports that feature. It says "Some DCS systems transmit a special “turn off code” at the end of each transmission. The turn off code causes a properly equipped receiver to mute before the transmission ends, eliminating the “squelch tail” burst of noise the commonly occurs when the signal is lost.")
 
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