Avoiding Control Channel Data Noise

[kd4wcl]

I just programmed my PRO-652 and my PRO-96 scanners using the Butel Software with local frequencies. Almost immediately I began hearing what I will call control channel data noise (buzzing sound) and the scanning stops until I scan again - and then it occurs again within a few seconds. I am fairly familiar with these scanners so I am not asking for specific help in how to use the scanner to fix this problem.

My question is how, in general terms "How do I keep from hearing the noise when still hearing "legit" transmissions when scanning"? I assume locking out the talk-group would prevent me from hearing other talk-groups.

I don't like to ask for help but have been searching this topic on RR and YouTube for hours this morning with no luck. Perhaps your response will help others too!

Thanks for your help in advance!

N9PQ (formally KD4WCL)

UPDATE:
I changed the Squelch mode to P25 and the noise stopped. I am not sure if this broke anything else, but it stopped the noise!

 

[DickH]

UPDATE:
I changed the Squelch mode to P25 and the noise stopped. I am not sure if this broke anything else, but it stopped the noise!

If you're not sure how trunking works, this may explain it.

MOTOROLA TRUNKING

The object of trunking is to allow many users to share a relatively few frequencies.
A trunking system is controlled by a computer. Information (data) is exchanged between the system radios and the computer on a control channel, sometimes called a data channel. It sounds like a strong buzz.

A large system can have up to 28 freqs., 4 of which may be used as control channels. The control channel may be changed once a day or as often as the programmer decides. Some scanners need only the control channels to track an entire system. Just put in the 4 Control Channels.

Each group of users (Fire, Police, etc.) is assigned TALK GROUPS. In a Motorola Type II system, the most common type, TGs are usually in 32 number steps starting with 16 and going up to 65536; 16, 48, 80 --- 4656, 4688, 4720 --- 28944, 28976, etc. System radios can have more than 100 TGs programmed into them.

After all the freqs. have been entered and it is "trunking", the Banks become SCAN LISTS where you enter the Talk Groups you want to hear. Use the Talk Group numbers in the DEC column.

When a user pushes the talk button on his radio, data is sent to the computer. The computer chooses an unused freq. and sends that data to all the radios using the TG of the originating unit. This all happens in a fraction of a second and it happens EVERY TIME a radio is used.

EXAMPLE:
Fire Dispatch calling Engine 4 (TG 4528 on 856.7125)
Engine 4 answering Dispatch (TG 4528 on 852.2625)
Respond to 73 Elm Street (TG 4528 on 855.9625)
Engine 4 responding (TG 4528 on 851.6375)

If you have entered TG 4528 into your scanner, it will decode the control channel data and change your scanner freqs. to follow the conversation on TG 4528.

 

[Spitfire8520]

My question is how, in general terms "How do I keep from hearing the noise when still hearing "legit" transmissions when scanning"? I assume locking out the talk-group would prevent me from hearing other talk-groups.

...

UPDATE:
I changed the Squelch mode to P25 and the noise stopped. I am not sure if this broke anything else, but it stopped the noise!

It would really depend on what you are programming into your scanner particularly. It sounds like you're programming a conventional frequency and not a talkgroup, so I'll address it as such. I would say you are likely hearing some kind of unsupported digital format (DMR/TRBO/etc.), or data transmissions. If what you're trying to listen to is analog voice, then programming the proper CTCSS or DCS might work to filter that out. If what you're seeking is P25, then setting it to P25 will restrict it to looking for P25 only transmissions.

 

[kd4wcl]

Yes, Spitfire. This seems to help. It appears to be a squelch mode problem and seems resolved now. Thanks for both of your help!!