landradi00
Member
- Joined
- Sep 6, 2019
- Messages
- 13
Hi folks, I finally got around to recording some audio and doing the spectrum plot from the SDS100 for analysis.
I have been experiencing a "warbling" in the background when listening to Seattle / King County Public Safety (KCERS) on Seattle Simulcast. This is a Motorola Type II SmartZone trunked system but it uses analog voice for effectively all communications of interest. I get the warbling regardless of RSSI, from -90 to -60 and regardless of noise level or location. I get the warbling regardless of power source, battery or plug.
I'm attaching here a screenshot. As you can see, after a brief no-signal period, there's a period of FM "full quieting" silence which has the warbling waveform, followed by speech, then more warbling. The warbling is obviously visible on the waveform.
I previously had thought this might be related to the known inverse-phase issue with the SDS audio out -- which by the way you can see in the waveform clearly. That is, perhaps the audio was clean but when I had it plugged into car speakers (which is when the warbling is worst) the phase issue might have been creating a perceived artifact. But in fact it shows up on the waveform straight from the headphone out jack into the computer sound card.
Also, the warbling does not show up in other modulation types. For example, broadcast FM -- although it has a smaller (tiny) hum, does not have the warble during full quieting parts. See the second screenshot for no warble broadcast FM. AM and digital modulation do not have it either. My analog-only Uniden BC330T does not exhibit the warble; see screenshot #3.
Global auto filter is "Auto" in this recording, but the warble seems to persist regardless of various settings, including "Off," which I've tried. The site (Seattle Simulcast) filter is set to Global.
Final hint here is that I can also reproduce the warble with the Port of Seattle system, which is also a SmartZone II analog trunked system.
1. Does anyone know why this warble exists?
2. Does anybody else get a similar warble under any circumstances, and if so, can you share what types of system and signals give it?
3. Any workarounds?
Thank you, fellow SDS'ers!
I have been experiencing a "warbling" in the background when listening to Seattle / King County Public Safety (KCERS) on Seattle Simulcast. This is a Motorola Type II SmartZone trunked system but it uses analog voice for effectively all communications of interest. I get the warbling regardless of RSSI, from -90 to -60 and regardless of noise level or location. I get the warbling regardless of power source, battery or plug.
I'm attaching here a screenshot. As you can see, after a brief no-signal period, there's a period of FM "full quieting" silence which has the warbling waveform, followed by speech, then more warbling. The warbling is obviously visible on the waveform.
I previously had thought this might be related to the known inverse-phase issue with the SDS audio out -- which by the way you can see in the waveform clearly. That is, perhaps the audio was clean but when I had it plugged into car speakers (which is when the warbling is worst) the phase issue might have been creating a perceived artifact. But in fact it shows up on the waveform straight from the headphone out jack into the computer sound card.
Also, the warbling does not show up in other modulation types. For example, broadcast FM -- although it has a smaller (tiny) hum, does not have the warble during full quieting parts. See the second screenshot for no warble broadcast FM. AM and digital modulation do not have it either. My analog-only Uniden BC330T does not exhibit the warble; see screenshot #3.
Global auto filter is "Auto" in this recording, but the warble seems to persist regardless of various settings, including "Off," which I've tried. The site (Seattle Simulcast) filter is set to Global.
Final hint here is that I can also reproduce the warble with the Port of Seattle system, which is also a SmartZone II analog trunked system.
1. Does anyone know why this warble exists?
2. Does anybody else get a similar warble under any circumstances, and if so, can you share what types of system and signals give it?
3. Any workarounds?
Thank you, fellow SDS'ers!