SDR# Trying SDR Again after 6 years

KB4SHP

KB4SHP

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I tried many times in years past around 2020. Well I have decided to try it again. Been looking an researching on here between Raspberry Pi 5 and Mini pc well last night I bought this
GMKtec G2 Plus Mini n150/12gb LPDDR5/512 SSD

My question is how many SDRs do you all recommend for the following trunking information

Also what software will work the best hopefully can get this going with you all help

Thanks
 

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RobDLG

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There are online tools that take the system frequencies and determine the required number of SDRs, with a center frequency for each. I've used this one in the past: iCAD TR Config Generator
 
boatbod

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The number of SDR dongles required depends on so many factors; software app choice, number of discrete systems to be monitored, number of simultaneous streams, etc. Some apps (e.g. sdrtrunk) require continuous receive coverage of the RF spectrum of the system to be monitored while other apps only need a small slice of spectrum and happily hop around following the voice traffic (e.g op25). It all depends what you want to achieve and how much you are prepared to spend. Personally I have taken a liking to HydraSdr devices because they can receive up to 10Mhz and have proven to be very stable and also quite sensitive compared to other hardware. I also own a bucket-load of generic RTLs, and they are so cheap as to be practically disposable. For a quick setup on a local P25 system they are hard to beat!

My primary streaming server actively monitors two geographically distant P25 systems (both part of Maryland FiRST) and runs 6 streams (5 to Broadcastify, 1 private) all from a single HydraSDR device running my own op25. I have browser audio locally and remote via wireguard vpn, and the broadcastify feeds are widely used within the community. Hardware is a NUC13 i7 that hardly breaks a sweat, and has several other things it does in the background. All this is undoubtedly possible with other apps such as trunkrecorder, sdrtrunk, and so on, but I'll let those with experience running those apps speak for them.

Good luck, and welcome to the fun!

1786553338419.png
 
KB4SHP

KB4SHP

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KB4SHP said:
I tried many times in years past around 2020. Well I have decided to try it again. Been looking an researching on here between Raspberry Pi 5 and Mini pc well last night I bought this
GMKtec G2 Plus Mini n150/12gb LPDDR5/512 SSD

My question is how many SDRs do you all recommend for the following trunking information

Also what software will work the best hopefully can get this going with you all help

Thanks
Click to expand...
This is yes my results on one tower would this mean I need 3 dongles for this site ?
 
Enforcer52

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If you are going to run all four systems at the same time on the same software (ie. SDRTrunk, etc.) you will need 6 sdrs at 2.4mhz band width like the RTL-SDRs. You will also need a good powered usb hub to power them all.

It is possible to get by with fewer depending on how you setup the systems using SDRTrunk. By combining the actual used control channel on a system, with other used control channels if within the 2.4mhz range, on a single sdr. Then after determining exactly how many sdrs are need for control channels then leaving the other sdrs with no assigned channels you might get by with 4 or 5 sdrs. But not being able to monitor the Viper system and play with the setup I can not determine that.

Legend​


  • Edge Frequency
  • Voice Frequency
  • Control Frequency
  • Center Frequency

Dongle 1​

2.4MS/s (Covered Frequencies: 7)
Frequency (MHz)Comment
769.072000000Lowest Edge
769.256250000Voice Channel
770.018750000Voice Channel
770.272000000Center Frequency
770.406250000Voice Channel
771.031250000Voice Channel
771.043750000Voice Channel
771.281250000Voice Channel
771.293750000Voice Channel
771.472000000Highest Edge

Dongle 2​

2.4MS/s (Covered Frequencies: 7)
Frequency (MHz)Comment
771.428000000Lowest Edge
771.781250000Voice Channel
771.793750000Voice Channel
772.343750000Voice Channel
772.628000000Center Frequency
772.731250000Voice Channel
772.743750000Voice Channel
772.993750000Voice Channel
773.481250000Voice Channel
773.828000000Highest Edge

Dongle 3​

2.4MS/s (Covered Frequencies: 2)
Frequency (MHz)Comment
773.469000000Lowest Edge
774.656250000Voice Channel
774.668750000Voice Channel
774.669000000Center Frequency
775.869000000Highest Edge

Dongle 4​

2.4MS/s (Covered Frequencies: 12)
Frequency (MHz)Comment
851.019000000Lowest Edge
851.050000000Voice Channel
851.062500000Voice Channel
851.412500000Voice Channel
851.575000000Voice Channel
851.625000000Voice Channel
851.900000000Voice Channel
852.062500000Voice Channel
852.200000000Voice Channel
852.219000000Center Frequency
852.662500000Voice Channel
852.812500000Voice Channel
853.187500000Voice Channel
853.375000000Voice Channel
853.419000000Highest Edge

Dongle 5​

2.4MS/s (Covered Frequencies: 3)
Frequency (MHz)Comment
852.547000000Lowest Edge
853.575000000Voice Channel
853.747000000Center Frequency
853.787500000Voice Channel
853.925000000Voice Channel
854.947000000Highest Edge

Dongle 6​

2.4MS/s (Covered Frequencies: 1)
Frequency (MHz)Comment
859.544000000Lowest Edge
860.737500000Voice Channel
860.744000000Center Frequency
861.944000000Highest Edge
 
Last edited:
boatbod

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If North Carolina VIPER is like Maryland FiRST there are one set of tgids defined across the whole system, and regional simulcast clusters of towers that carry traffic for each jurisdiction/user of the system. Each of these clusters will dynamically participate in broadcasting tgid traffic based on whether or not there are subscriber radios affiliated with that tgid in their reception area. Traffic on (for example) tgid 1000 will be receivable from any site that has an active affiliation, meaning you don't need to monitor all sites at all times, just the one site where there is always an subscriber radio affiliated with tgid 1000.

The challenge becomes interesting when you want to monitor geographically disparate agencies where the subscribers don't often cross simulcast boundaries. Their traffic will tend to only be found on their home simulcast site, which means you will need to monitor both simulcast systems to get both sets of traffic.
 
jblackst

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But can you receive all 4 sites from your location?

Either way, the 800 sites will need 3 dongles (that single 860 channel drives you to the third one), the 700 sites will need 3 dongles (based on that frequency calculator and my experience on next door on TACN). If you're just interested in seeing the control channels, you could get away with a total of 2 dongles, one for each band, but if you want to listen to the sites you'll need additional dongles to allow one dongle to stay tuned in to the CC and the others to follow the voice traffic. Most dongles have a cap at 2.4 MHz of bandwidth, so a rough figure of one dongle per 2.4 MHz is a decent place to start (but that frequency calculator site is a better place: https://alertapi.alertpage.net/sdr/ or iCAD TR Config Generator ).

As someone else posted, if you're running that many dongles, you'll want to get a powered USB hub to feed them, as you'll have difficulty getting that much power upstream from a non-powered hub with any degree of reliability. My setup here has 7 dongles on a single 10 port powered USB hub and runs just fine, monitoring several 700 and 800 sites (much like you are intending). Then, if you're looking at running 6 dongles, you'll likely want to invest in a good antenna, inline amplifier, and a multi-coupler to get all of them fed with quality signal.

If you choose to go the route of an AirSpy to take advantage of the 10 MHz bandwidth, just be aware that the AirSpy seems to use more processing power for that 10 MHz than 4 other SDRs. I have a single AirSpy and the only way I can get it to run reliably is to give it space on a different USB port from the other SDRs.
 
KB4SHP

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boatbod said:
If North Carolina VIPER is like Maryland FiRST there are one set of tgids defined across the whole system, and regional simulcast clusters of towers that carry traffic for each jurisdiction/user of the system. Each of these clusters will dynamically participate in broadcasting tgid traffic based on whether or not there are subscriber radios affiliated with that tgid in their reception area. Traffic on (for example) tgid 1000 will be receivable from any site that has an active affiliation, meaning you don't need to monitor all sites at all times, just the one site where there is always an subscriber radio affiliated with tgid 1000.

The challenge becomes interesting when you want to monitor geographically disparate agencies where the subscribers don't often cross simulcast boundaries. Their traffic will tend to only be found on their home simulcast site, which means you will need to monitor both simulcast systems to get both sets of traffic.
Click to expand...
Some areas of the Viper system are simulcast however my county isn’t. That is why I need to scan all 4 sites.because the talk groups don’t always affiliate with every tower. I was using a blue tail P25RX however the support for it has ended due to the guy who created them passed. So I am hoping this Hydra will do the trick along with the right software I ordered one today
 
KB4SHP

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Enforcer52 said:
If you are going to run all four systems at the same time on the same software (ie. SDRTrunk, etc.) you will need 6 sdrs at 2.4mhz band width like the RTL-SDRs. You will also need a good powered usb hub to power them all.

It is possible to get by with fewer depending on how you setup the systems using SDRTrunk. By combining the actual used control channel on a system, with other used control channels if within the 2.4mhz range, on a single sdr. Then after determining exactly how many sdrs are need for control channels then leaving the other sdrs with no assigned channels you might get by with 4 or 5 sdrs. But not being able to monitor the Viper system and play with the setup I can not determine that.

Legend​


  • Edge Frequency
  • Voice Frequency
  • Control Frequency
  • Center Frequency

Dongle 1​

2.4MS/s (Covered Frequencies: 7)
Frequency (MHz)Comment
769.072000000Lowest Edge
769.256250000Voice Channel
770.018750000Voice Channel
770.272000000Center Frequency
770.406250000Voice Channel
771.031250000Voice Channel
771.043750000Voice Channel
771.281250000Voice Channel
771.293750000Voice Channel
771.472000000Highest Edge

Dongle 2​

2.4MS/s (Covered Frequencies: 7)
Frequency (MHz)Comment
771.428000000Lowest Edge
771.781250000Voice Channel
771.793750000Voice Channel
772.343750000Voice Channel
772.628000000Center Frequency
772.731250000Voice Channel
772.743750000Voice Channel
772.993750000Voice Channel
773.481250000Voice Channel
773.828000000Highest Edge

Dongle 3​

2.4MS/s (Covered Frequencies: 2)
Frequency (MHz)Comment
773.469000000Lowest Edge
774.656250000Voice Channel
774.668750000Voice Channel
774.669000000Center Frequency
775.869000000Highest Edge

Dongle 4​

2.4MS/s (Covered Frequencies: 12)
Frequency (MHz)Comment
851.019000000Lowest Edge
851.050000000Voice Channel
851.062500000Voice Channel
851.412500000Voice Channel
851.575000000Voice Channel
851.625000000Voice Channel
851.900000000Voice Channel
852.062500000Voice Channel
852.200000000Voice Channel
852.219000000Center Frequency
852.662500000Voice Channel
852.812500000Voice Channel
853.187500000Voice Channel
853.375000000Voice Channel
853.419000000Highest Edge

Dongle 5​

2.4MS/s (Covered Frequencies: 3)
Frequency (MHz)Comment
852.547000000Lowest Edge
853.575000000Voice Channel
853.747000000Center Frequency
853.787500000Voice Channel
853.925000000Voice Channel
854.947000000Highest Edge

Dongle 6​

2.4MS/s (Covered Frequencies: 1)
Frequency (MHz)Comment
859.544000000Lowest Edge
860.737500000Voice Channel
860.744000000Center Frequency
861.944000000Highest Edge
Click to expand...
Thank you for the information that was problem my problem years ago only was using 2 dongles
 
Enforcer52

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Have you decided what software you are going to use yet?

You may run into duplicate transmissions monitoring 4 towers capable of all carrying the same traffic.
 
KB4SHP

KB4SHP

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jblackst said:
But can you receive all 4 sites from your location?

Either way, the 800 sites will need 3 dongles (that single 860 channel drives you to the third one), the 700 sites will need 3 dongles (based on that frequency calculator and my experience on next door on TACN). If you're just interested in seeing the control channels, you could get away with a total of 2 dongles, one for each band, but if you want to listen to the sites you'll need additional dongles to allow one dongle to stay tuned in to the CC and the others to follow the voice traffic. Most dongles have a cap at 2.4 MHz of bandwidth, so a rough figure of one dongle per 2.4 MHz is a decent place to start (but that frequency calculator site is a better place: https://alertapi.alertpage.net/sdr/ or iCAD TR Config Generator ).

As someone else posted, if you're running that many dongles, you'll want to get a powered USB hub to feed them, as you'll have difficulty getting that much power upstream from a non-powered hub with any degree of reliability. My setup here has 7 dongles on a single 10 port powered USB hub and runs just fine, monitoring several 700 and 800 sites (much like you are intending). Then, if you're looking at running 6 dongles, you'll likely want to invest in a good antenna, inline amplifier, and a multi-coupler to get all of them fed with quality signal.

If you choose to go the route of an AirSpy to take advantage of the 10 MHz bandwidth, just be aware that the AirSpy seems to use more processing power for that 10 MHz than 4 other SDRs. I have a single AirSpy and the only way I can get it to run reliably is to give it space on a different USB port from the other SDRs.
Click to expand...
Yes I can receive all 4. Thank you for reply I am trying to get all this input before start this project
 
KB4SHP

KB4SHP

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Enforcer52 said:
Have you decided what software you are going to use yet?

You may run into duplicate transmissions monitoring 4 towers capable of all carrying the same traffic.
Click to expand...
Haven’t decided yet
 
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