Digital and PL tones

[Steve]

I saw something interesting/strange (at least to me) today. While scanning and searching I had a local agency frequency to go active with digital traffic (P25 type) and my scanners displayed a PL tone on the frequency. It occurred on the scanner that was scanning and the scanner that was in search mode. Both scanners displayed the same PL tone.
So my question, is this possible or was my scanners acting "possessed"?
Both scanners used were analog, I didn't have access to my digital scanners.

 

[Grog]

False tones. Like false labor but with no pregnancy.

 

[Steve]

Okay I can understand that, only thing is on the scanner in scan mode the PL tone is stored for that particular channel and on the scanner in search mode the PL tone was the same as the stored one.
That is what puzzled me. Of course it could just be that the scanners are "haunted". Just one more crazy thing going on in Alabama of late.

 

[N_Jay]

Nothing surprising. The digital waveform has significant low frequency energy. One of the components was strong enough and stable enough to be detected a PL.

 

[CCHLLM]

As NJH posted, the low frequency components of the digital modulation have plenty of PL range components. In fact, it's not unusual to see some scanners in analog search mode pop-up PLs in the 130s when P25 modulation is present. At least that's been my observation around the little beasties in the shop.

 

[Steve]

Thanks for information. I had never noticed or saw the condition happen before and was puzzled.