Missing Radio Traffic

[Nate1n22]

I have SDRTrunk setup to only monitor the police dispatch channel and broadcast to Broadcastify. I have a blacklist setup to only have it play PD dispatch. I am missing a lot of transmissions. I have 2 RTL dongles. Should I add more dongles to help improve this?

 

[mattwillson]

What's does it show in the call activity log? If you see Group Call - Rejected Tuner Unavailable then it would indicate that more dongle bandwidth is needed.

 

[Nate1n22]

What's does it show in the call activity log? If you see Group Call - Rejected Tuner Unavailable then it would indicate that more dongle bandwidth is needed.

Getting a lot of "Group Call - Rejected - Tuner Unavailable Phase 1 Channel Grant"
What's the best way to determine how many dongles I need? I am monitoring 853.9875 as my control

 

[mattwillson]

An RTL-SDR dongle has a maximum usable bandwidth of about 2.4 MHz. The site you are monitoring is spread over 5.7875 MHz (857.1375 - 851.350), one more dongle would provide the needed coverage for the site.

 

[Nate1n22]

An RTL-SDR dongle has a maximum usable bandwidth of about 2.4 MHz. The site you are monitoring is spread over 5.7875 MHz (857.1375 - 851.350), one more dongle would provide the needed coverage for the site.

Thanks. I just ordered another dongle. Can I run all 3 dongles with 1 antenna?

 

[Nate1n22]

I have heard possibly that my county is only using digital portables as of now. They just went live on 800 this week. I think they might still have analog in car radios. This might explain why I'm not picking up all the PD traffic

 

[AM909]

Thanks. I just ordered another dongle. Can I run all 3 dongles with 1 antenna?

I use an RCA DT-140M CATV (powered) drop amp / 4-way splitter. Spec is forward gain of 4 dB @ 54-1000 MHz. Yes, it's 75-ohm, probably a crappy noise figure, and you may be adding some more loss with adapters back and forth to F-connectors if you don't want to build/buy cables, but as long as you're not trying to squeeze every bit out of weak signals, it works fine. Available in your local home electronics store for <$30.

 

[maus92]

The second dongle is free to tune to any system frequency, thus is not constrained to monitor a fixed portion of the spectrum - unless it is currently decoding a channel. In this case, if another tg started using a channel more than +/- .8 MHz from the currently tuned channel, you would get a Tuner Unavailable message. A third dongle would also be free to tune any system frequency (channel) and would mitigate this situation. Or you could purchase a SDR that has a wider band width, like an AirSpy R2.

 

[Nate1n22]

Got my third dongle, plugged it in and now I am getting SYNC LOSS - BITS PROCESSED in my messages. Unplug the new dongle and it works fine.

 

[iMONITOR]

I have SDRTrunk setup to only monitor the police dispatch channel and broadcast to Broadcastify. I have a blacklist setup to only have it play PD dispatch. I am missing a lot of transmissions. I have 2 RTL dongles. Should I add more dongles to help improve this?

You're in Michigan monitoring MPSCS. You're most likely experiencing simulcast issues. More dongles won't help with that at all. What are you using for an antenna and where is it located?

 

[maus92]

Are you saying that SDRTrunk is being affected by simulcast distortion? This is probably the first instance I've heard of the program not handling the issue well. Can you provide more examples? SDRTrunk and OP25 seem to handle the P25P2 simulcast cell I monitor (Anne Arundel on Maryland FIRST) with no issues. Same goes for the G5 and SDS200. But simulcast issues are often location specific, and can affect system subscribers as well. The OP also mentions a program generated error noting lack of tuner resources, so simulcast distortion may not be the only culprit.

 

[mattwillson]

SYNC LOSS would indicate a signal problem. What your using to split the antenna is a possibility. The dongle could be off center and need the PPM adjusted. You can try increasing the gain to see if that helps.

 

[iMONITOR]

Are you saying that SDRTrunk is being affected by simulcast distortion? This is probably the first instance I've heard of the program not handling the issue well. Can you provide more examples? SDRTrunk and OP25 seem to handle the P25P2 simulcast cell I monitor (Anne Arundel on Maryland FIRST) with no issues. Same goes for the G5 and SDS200. But simulcast issues are often location specific, and can affect system subscribers as well. The OP also mentions a program generated error noting lack of tuner resources, so simulcast distortion may not be the only culprit.

Well I'm not certain that's the problem. The G5 and SDS200 are designed to handle simulcast well without distortion or drop outs. While I don't have any experience iwth SDRTrunk or OP25 (although I plan to get into that soon), I'm not aware if it's immune to the problem associated with simulcast. Michigan's MPSCS can be a challenge. Macomb County where I live has 14 tower sites on one control channel.

 

[Nate1n22]

It's not simulcast distortion. What the above poster put is what I think is happening. Seems like SDRTrunk picks up on channels that I have black listed but doesn't play what's on there and doing that it misses the PD dispatch channel I am trying to stream. This only happens every now and then. Everything else is working great.
No antenna splitter. Using the stock antenna that came with the RTL dongles.

 

[ChrisABQ]

I've heard over and over that the average range for an RTL SDR dongle is 2.4 mhz, BUT, how many simultaneous TG's can one dongle handle? I currently have 3 dongles but I'm wondering if I need a 4th.

 

[maus92]

I've heard over and over that the average range for an RTL SDR dongle is 2.4 mhz, BUT, how many simultaneous TG's can one dongle handle? I currently have 3 dongles but I'm wondering if I need a 4th.

Depends on how many VFOs are enabled. Theoretical bw is 2.4 MHz, but it matters where the center channel of a dongle is assigned - and practical bw is slightly less than 2 MHz. I have 4 VFOs enabled on the AirSpy R4, and a seperate Nooelec SDR is locked on the cch. There are 2 VFOs on the Nooelec, so it will occasionally decode a traffic channel within +/- .9 MHz or so from the cch frequency, but most voice traffic seems to be shunted to the AirSpy. The program is configured to output mono, so I am only hearing one traffic channel even though up to 5 could theoretically be streamed simultaneously. Having numerous VFOs does eat up CPU resources, so one thing the OP can check is how hard is the host computer working...

 

[AM909]

... Having numerous VFOs does eat up CPU resources, so one thing the OP can check is how hard is the host computer working...

That's my read, based on OP writing "Got my third dongle, plugged it in and now I am getting SYNC LOSS - BITS PROCESSED in my messages. Unplug the new dongle and it works fine."

@Nate1n22: Sounds like a lack of resources somewhere. How are the dongles connected? Three separate USB ports, or an external hub? Even if they are separate ports on your computer, if there are more available, you may be able to move one or more to different ports that are on different internal USB controllers.

Also, I remember SDRTrunk having an option somewhere that changes how it performs. One setting is supposed to work better (and chew less CPU) with a larger number of systems or talk groups or freqs or something like that. What's your CPU usage look like (Ctrl-Shift-Esc if on Windows)?

 

[Nate1n22]

That's my read, based on OP writing "Got my third dongle, plugged it in and now I am getting SYNC LOSS - BITS PROCESSED in my messages. Unplug the new dongle and it works fine."

@Nate1n22: Sounds like a lack of resources somewhere. How are the dongles connected? Three separate USB ports, or an external hub? Even if they are separate ports on your computer, if there are more available, you may be able to move one or more to different ports that are on different internal USB controllers.

Also, I remember SDRTrunk having an option somewhere that changes how it performs. One setting is supposed to work better (and chew less CPU) with a larger number of systems or talk groups or freqs or something like that. What's your CPU usage look like (Ctrl-Shift-Esc if on Windows)?

Attached via 3 separate USB ports on the PC. Tried moving the dongle around and no luck. I noticed when I plug in the 3rd dongle there's no control tab on the "Now Playing" screen. It just says "idle"
CPU stays around 15%

 

[maus92]

Attached via 3 separate USB ports on the PC. Tried moving the dongle around and no luck. I noticed when I plug in the 3rd dongle there's no control tab on the "Now Playing" screen. It just says "idle"
CPU stays around 15%

Using separate ports does not guarantee splitting the load to different controllers. Ports that share a controller share its max practical (not theoretical) band width and current output.

 

[Nate1n22]

Moved all the dongles around and it seems to be working now