SDRTrunk Missing transmissions guidance

[D3m0nicSoul]

Hello everyone,

I currently run SDRTrunk and RDIOScanner on linux with 2 Airspy Mini's. I have read all the SDR documentation I can find but still seem to be having issues where it will miss transmissions. To start off, can anyone confirm 2 Mini's will cover the Camden County NJ Public safety frequency? (Camden County Public Safety Trunking System, Camden County, New Jersey) If so, is there any setting I should check or things I should confirm or rule out? Seems to be random maybe at times of high traffic?

 

[jtwalker]

Just Countywide Simulcast site? Or Camden also?

 

[D3m0nicSoul]

Camden also

 

[jtwalker]

And an Airspsy Mini is rated for 6 MHz of spectrum each right? Looks like two should cover both sites by my quick calculations.

Funny how the frequencies assigned to the countywide site jump between 700 and 800. Unusual in my experience for one site.

 

[D3m0nicSoul]

Yea 6mhz. The one tuner stays locked I guess due to the control channel. The other one seems to lock around the 800mhz frequency.

 

[RMason]

To start off, can anyone confirm 2 Mini's will cover the Camden County NJ Public safety frequency? (Camden County Public Safety Trunking System, Camden County, New Jersey) If so, is there any setting I should check or things I should confirm or rule out?

Do you get any messages indicating "No Tuner Available" (or similar) in the terminal window?

And an Airspsy Mini is rated for 6 MHz of spectrum each right? Looks like two should cover both sites by my quick calculations.

Assuming 6Mhz of spectrum, it looks like 3 Airspy MINIs will be required to cover both the Countywide Simulcast and Camden City sites. All of the 700Mhz frequencies fit within 6Mhz. However, the 800Mhz frequencies span more than 6Mhz :

1) 769.80625 - 774.19375​

2) 851.1625 - 857.1375​

3) 857.6625 - 859.0375​

 

[jtwalker]

Do you get any messages indicating "No Tuner Available" (or similar) in the terminal window?


Assuming 6Mhz of spectrum, it looks like 3 Airspy MINIs will be required to cover both the Countywide Simulcast and Camden City sites. All of the 700Mhz frequencies fit within 6Mhz. However, the 800Mhz frequencies span more than 6Mhz :

1) 769.80625 - 774.19375​

2) 851.1625 - 857.1375​

3) 857.6625 - 859.0375​

Thanks for correcting me. I was looking on a phone and it’s hard to take iall frequencies in at once.

 

[BinaryMode]

Correct me if I'm wrong, but isn't the county wide simulcast some 89 MHz of bandwidth taking into consideration 769.80625 is the lowest frequency and 859.0375 is the highest? I mean, in order to track correctly for this system in particular one would need that bandwidth, correct?

Edit-

2) 851.1625 - 857.1375 spans 5.975 MHz.

 

[RMason]

Correct me if I'm wrong, but isn't the county wide simulcast some 89 MHz of bandwidth taking into consideration 769.80625 is the lowest frequency and 859.0375 is the highest? I mean, in order to track correctly for this system in particular one would need that bandwidth, correct

Although the system contains frequencies between 769.80625 and 859.0375, there are no transmitters in the range between 774.19375 and 851.1625. There is no need to cover this 77Mhz gap.

1) 769.80625 - 774.19375
2) 851.1625 - 857.1375
3) 857.6625 - 859.0375

 

[D3m0nicSoul]

Do you get any messages indicating "No Tuner Available" (or similar) in the terminal window?


Assuming 6Mhz of spectrum, it looks like 3 Airspy MINIs will be required to cover both the Countywide Simulcast and Camden City sites. All of the 700Mhz frequencies fit within 6Mhz. However, the 800Mhz frequencies span more than 6Mhz :

1) 769.80625 - 774.19375​

2) 851.1625 - 857.1375​

3) 857.6625 - 859.0375​

I have not noticed any tuner not available messages but I only notice missing transmissions at certain times. For example I'll hear county say something then they will speak again after a minute or so acknowledging the unit response that I didn't hear.

You mentioned 3 airspy minis is that even with no transmitters from 774.19375 and 851.1625

And lastly just to confirm the 6mhz is the sample rate setting on the tuner settings screen? I believe it can be set to either 3mhz or 6mhz

 

[RMason]

I have not noticed any tuner not available messages but I only notice missing transmissions at certain times. For example I'll hear county say something then they will speak again after a minute or so acknowledging the unit response that I didn't hear.

If you are missing transmissions due to not having enough sdr's to fully cover the two sites, you should be getting "No Tuner Available" messages. Look in sdrtrunk_app.log for clues.

You mentioned 3 airspy minis is that even with no transmitters from 774.19375 and 851.1625

Yes. You will need 3 airspy minis to fully cover both sites. You can add another sdr type as long as it provides an additional 2Mhz of bandwidth. It doesn't have to be another airspy mini.

Each mini provides 6Mhz of bandwidth.

• One mini is required to cover 769.80625 - 774.19375 (4.4Mhz)
• Two mini are required to cover 851.1625 - 859.0375 (8Mhz)

And lastly just to confirm the 6mhz is the sample rate setting on the tuner settings screen? I believe it can be set to either 3mhz or 6mhz

Correct. It will need to be configured for the 6Mhz sample rate.

Just Countywide Simulcast site? Or Camden also?

Camden also

Do you need to cover both sites? Does the Camden site provide coverage not included in the Countywide Simulcast site?

 

[jtwalker]

One other possibility for missing transmission using just SDR-Trunk is when more than two transmissions occur at same time. You only have two audio channels, left and right, so you can only listen to two concurrent transmissions. The way around this is to record in SDR-T but not listen, then send recorded audio into RDIO-scanner or another application.

 

[RMason]

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[D3m0nicSoul]

If you are missing transmissions due to not having enough sdr's to fully cover the two sites, you should be getting "No Tuner Available" messages. Look in sdrtrunk_app.log for clues.

Yes. You will need 3 airspy minis to fully cover both sites. You can add another sdr type as long as it provides an additional 2Mhz of bandwidth. It doesn't have to be another airspy mini.

Each mini provides 6Mhz of bandwidth.

• One mini is required to cover 769.80625 - 774.19375 (4.4Mhz)
• Two mini are required to cover 851.1625 - 859.0375 (8Mhz)

Correct. It will need to be configured for the 6Mhz sample rate.



Do you need to cover both sites? Does the Camden site provide coverage not included in the Countywide Simulcast site?

I believe Camden has its own channel that isn't included in any of the ops channels. I could be wrong though.

One other possibility for missing transmission using just SDR-Trunk is when more than two transmissions occur at same time. You only have two audio channels, left and right, so you can only listen to two concurrent transmissions. The way around this is to record in SDR-T but not listen, then send recorded audio into RDIO-scanner or another application.

I currently have it streaming to RDIOscanner that should be ok right?

Appreciate everyone's help. How many airspy minis for Gloucester County? Gloucester County Public Safety Trunking System, Gloucester County, New Jersey

 

[dave3825]

For each site, what are you max traffic channels set to? Seem to remember reading you need 2 per each voice freq if phase 2. But I'm still banged up from last night.

 

[D3m0nicSoul]

For each site, what are you max traffic channels set to? Seem to remember reading you need 2 per each voice freq if phase 2. But I'm still banged up from last night.



View attachment 173598

Its currently set to 10