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]

<deleted>

 

[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

 

[RMason]

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

The Gloucester simulcast site spans from 771.45625 to 774.69375. This is 3.25Mhz. This site fits within the bandwidth of a single airspy mini.

You are currently monitoring the Camden County simulcast site which includes frequencies from 769.80625 to 774.19375. Since the Cloucester and Camden 700Mhz frequencies overlap and span only 4.4Mhz, you will not need to add another tuner to cover the Gloucester site. One airspy mini can cover the 700Mhz frequencies for both Gloucester and Camden Counties. (You need 3 sdr minis to cover all 3 sites in Camden and Gloucester counties)

Gloucester County:

1 (1)	001 (1)	Simulcast	771.45625	771.46875	771.90625	771.91875	772.20625c	772.21875	772.60625c	772.61875
			772.95625c	772.96875	774.68125c	774.69375

Camden County:

1 (1)	001 (1)	Countywide Simulcast	769.80625	769.81875	770.25625	770.26875	770.85625	770.86875c	771.20625	771.21875
			772.10625	772.11875c	772.88125	772.89375	773.45625	773.46875c	773.93125	773.94375
			774.18125	774.19375c	854.1375	854.1875	854.3625	857.1375	857.6625	858.6875
			859.0375
1 (1)	002 (2)	Camden City	851.1625	851.7375c	852.7875c	853.1875c	853.700c

 

[maus92]

Some versions of SDRT allow the user to configure the band spread of each individual SDR. I would set sdr1 to 769.000 - 775.000; sdr2 to 854.000 - 860.000; and if you need the Camden City site, you will need an additional airspy mini sdr3 set to 851.000 - 854.000.

 

[mtindor]

Its currently set to 10

You have N-1 voice frequencies available at any given time on each site, with the remaining "1" being the current control channel.

Gloucester: 12-1 = 11 max voice channels on your 700 mhz SDR tuner
Camden Co "Countywide Simulcast": 18-1 = 17 max voice channels on your 700 mhz SDR tuner, 7 on your first 800 mhz SDR tuner
Camden Co "Camden City": 5-1 = 4 max voice channels on your second 800 mhz SDR tuner

For the 800 stuff you really have options of how many channels you are going to cover with each of the two 800 Airspy minis.

Obviously, all of the 700 mhz frequencies across all of the sites can be handled on one single Airspy mini tuner. You'd need a total of 28 max traffic channels on that single tuner.

Depending upon whether or not you are going to monitor Gloucester and/or Camden City, you will need at least 7 max voice channels on a single Airpsy Mini for the 800 band, or if monitoring all three sites you'll need a third Airspy mini and you'll need to cover 11 max voice channels between the two 800 mhz minis. How you split those 800 mhz freqs up wilil determine how many of the 11 max voice channels are set on one tuner and how many are set on the other

Certainly, with 10 max channels in use right now, even monitoring just the simulcast with two Airspy minis, you are going to be "missing" conversations when the system is busy. You need 17 max voice channels on the 700 mhz tuner and 7 max voice channels on the 800 mhz tuner just for the simulcast.

Of course, I was under the impression that you really don't get the performance of the full "6 mhz" because of degraded performance at the edges. I always plan for 8 mhz on an Airspy R2 and 5 mhz on an Airspy mini. I could be wrong though, and you may have 100% max performance (reception / rejection / sensitivity / selectivity) across the whole 6 mhz of a mini or 10 mhz of an R2.

 

[D3m0nicSoul]

Some versions of SDRT allow the user to configure the band spread of each individual SDR. I would set sdr1 to 769.000 - 775.000; sdr2 to 854.000 - 860.000; and if you need the Camden City site, you will need an additional airspy mini sdr3 set to 851.000 - 854.000.

I'll ignore Camden City for now. It looks like in the current Beta 3 I can set the frequency on the specific tuner so I did this for the first 2 you recommended.

You have N-1 voice frequencies available at any given time on each site, with the remaining "1" being the current control channel.

Gloucester: 12-1 = 11 max voice channels on your 700 mhz SDR tuner
Camden Co "Countywide Simulcast": 18-1 = 17 max voice channels on your 700 mhz SDR tuner, 7 on your first 800 mhz SDR tuner
Camden Co "Camden City": 5-1 = 4 max voice channels on your second 800 mhz SDR tuner

For the 800 stuff you really have options of how many channels you are going to cover with each of the two 800 Airspy minis.

Obviously, all of the 700 mhz frequencies across all of the sites can be handled on one single Airspy mini tuner. You'd need a total of 28 max traffic channels on that single tuner.

Depending upon whether or not you are going to monitor Gloucester and/or Camden City, you will need at least 7 max voice channels on a single Airpsy Mini for the 800 band, or if monitoring all three sites you'll need a third Airspy mini and you'll need to cover 11 max voice channels between the two 800 mhz minis. How you split those 800 mhz freqs up wilil determine how many of the 11 max voice channels are set on one tuner and how many are set on the other

Certainly, with 10 max channels in use right now, even monitoring just the simulcast with two Airspy minis, you are going to be "missing" conversations when the system is busy. You need 17 max voice channels on the 700 mhz tuner and 7 max voice channels on the 800 mhz tuner just for the simulcast.

Of course, I was under the impression that you really don't get the performance of the full "6 mhz" because of degraded performance at the edges. I always plan for 8 mhz on an Airspy R2 and 5 mhz on an Airspy mini. I could be wrong though, and you may have 100% max performance (reception / rejection / sensitivity / selectivity) across the whole 6 mhz of a mini or 10 mhz of an R2.

Is the Max Traffic channels setting per tuner or global between all tuners? Seeing my response above can I just set this to 24?

Side note I noticed I am seeing some Sync Loss - Bits Processed messages in the Messages tab. Is this normal? If not, what should I look at to resolve this?