SDRTrunk Missing Transmissions

[BrandonMace]

My SDRTrunk seems to be missing some transmissions between chatters or missing the first call completely.

SDRTrunk v0.6.1-beta 1
RTL-SDR Blog R828D RTL2832U Dongle
RaTLSnake M6 v2 Antenna
Windows 10 with 16GB ram and Core i7-6700 (ethernet wired to 1gig fiber service)

I am also running Trunking Recorder and rdio server the computer as well.

I am connected to Nicollet Co tower on ARMER and pick up quite a bit of traffic but I also seem to miss quite a few calls. I have a BCD436HP radio that will pick up more traffic from the Nicollet tower but the sdr seems to miss quite a few calls. Is there anything that I can adjust to try and pick up almost every single call or no matter what, it's still going to miss calls regardless? Let me know if i'm missing any information here.

TIA!

 

[maus92]

How many dongles do you have? If you are using only one, there may be times when one of the site frequencies is out of its bandwidth. Add another one, or get a wideband SDR like an Airspy or RSP1.

 

[BrandonMace]

How many dongles do you have? If you are using only one, there may be times when one of the site frequencies is out of its bandwidth. Add another one, or get a wideband SDR like an Airspy or RSP1.

Just using the 1 rtl dongle currently. Assuming it would be best to get another one and split the frequencies between the two or get an Airspy or RSP1?

 

[BrandonMace]

Also, I forgot to post some SDRTrunk screenshots..

 

[maus92]

The cheaper route would be adding another rtl dongle, but then you would need another antenna or use a splitter/combiner. However I use wideband sdrs because they are more flexible.

 

[jtwalker]

You don’t have to split the frequencies. Just having both dongles available to SDR-Trunk will suffice. My quick calculations of the frequencies you show in screenshot show that you need 2 dongles. Subtract lowest frequency from highest (control and voice) and if what you get is < 2.4 then one dongle will work, <4.8 then two, as so on.

 

[Enforcer52]

Also if you get a channel stuck in TEARDOWN as shown in one of the pics, that can change you effective range on bandwidth, and you would need to restart the system.

 

[BrandonMace]

You don’t have to split the frequencies. Just having both dongles available to SDR-Trunk will suffice. My quick calculations of the frequencies you show in screenshot show that you need 2 dongles. Subtract lowest frequency from highest (control and voice) and if what you get is < 2.4 then one dongle will work, <4.8 then two, as so on.

If I purchased another dongle, I would just have to plug it into computer with an antenna but wouldn't need to set any frequencies on it and it would do it's own magic?

 

[Enforcer52]

You would have to give the second SDR a different serial number first using the zadig utililty, then connect antenna. Then the magic happens.

 

[maus92]

I didn't know that Zadig has a tool to change rtl firmware / change the device's SN.

 

[jtwalker]

I didn't know that Zadig has a tool to change rtl firmware / change the device's SN.

I believe you are correct … ‘rtl-tools’ or something to that effect?

 

[maus92]

I believe you are correct … ‘rtl-tools’ or something to that effect?

rtltool is one of the utilities that you can use to change the SN. I believe there are other programs as well, just not Zadig.

 

[Enforcer52]

My bad, my fingers were typing faster than my brain, it is rtl_eeprom to change the serial number.

 

[mtindor]

Someone else has already indicated that you will need to two dongles. but you will also need to make sure that you configure the system with the proper number of "Max Traffic Channels". For instance, if you are monitoring a Phase I P25 system with an active control channel at any given time and 7 voice channels, then you want to set Max Traffic Channels to 7.

 

[GTR8000]

Someone else has already indicated that you will need to two dongles. but you will also need to make sure that you configure the system with the proper number of "Max Traffic Channels". For instance, if you are monitoring a Phase I P25 system with an active control channel at any given time and 7 voice channels, then you want to set Max Traffic Channels to 7.

And for a TDMA system, you only need to set the max traffic channels to the amount of repeaters/frequencies in use for traffic channels; you don't need to double it to account for each voice slot.

Although frankly if you're setting that to the max per site, it really doesn't matter if you set it to 7 or 999, you're basically telling it no limitations as to how many dynamic traffic channels the software can create. The setting is kind of moot if you have a PC with enough horsepower to keep up with decoding a lot of simultaneous traffic, just make sure that you set it high enough to capture them all. The setting is really more appropriate for those who need to limit the amount of decoding the software is performing, so you might set it lower than the actual amount of traffic channels to conserve CPU resources.

 

[BrandonMace]

Appreciate all the info! If I wanted to monitor the Janesville tower as well, I'm assuming that would require 3 dongles just alone for that tower? Or would any Airspy device be able to monitor both towers without having to use multiple sdr dongles? If so, which airspy device would be the best for this scenario?

 

[mtindor]

Appreciate all the info! If I wanted to monitor the Janesville tower as well, I'm assuming that would require 3 dongles just alone for that tower? Or would any Airspy device be able to monitor both towers without having to use multiple sdr dongles? If so, which airspy device would be the best for this scenario?

3 RTLs, or 1 RTL and an Airspy Mini, or a single Airspy R2. If it were me [and if you can afford it] I'd probably go with two Airspy minis rather than 3 RTLs or an Airspy R2. Having multiple devices makes things much more flexible when it comes to running multiple systems/sites in SDRTrunk. With that said, I cover two P25 systems on 800 mhz using a single Airspy R2 without issues. But I'd also have no problem using two Airspy minis instead.

 

[BrandonMace]

3 RTLs, or 1 RTL and an Airspy Mini, or a single Airspy R2. If it were me [and if you can afford it] I'd probably go with two Airspy minis rather than 3 RTLs or an Airspy R2. Having multiple devices makes things much more flexible when it comes to running multiple systems/sites in SDRTrunk. With that said, I cover two P25 systems on 800 mhz using a single Airspy R2 without issues. But I'd also have no problem using two Airspy minis instead.

Great info. Just curious what antenna you are using? Also is there a max distance in miles you can be away from a tower site? For example, I’m about 10 miles away from the Nicollet tower I’m pulling from but the Janesville tower is about 15-20 miles away that I’m wanting to connect to next.

 

[mtindor]

Great info. Just curious what antenna you are using? Also is there a max distance in miles you can be away from a tower site? For example, I’m about 10 miles away from the Nicollet tower I’m pulling from but the Janesville tower is about 15-20 miles away that I’m wanting to connect to next.

Depends upon location. Some locations I use an 800 yagi inside. Some locations I use an external VHF/UHF vertical. Some locations I use just the cheesy ccrappy telescoping antennas that come with RTL dongles (when I know I'm only going to be monitoring things close by).

If you are not going to have an external antenna, or a real gain antenna like an 800 yagi inside, then at least use Remtronics 800 mhz ducky antennas as they are the best [in my book] out there as far as duckys go.

And whether or not you can pull in stuff 10/15/20 miles away with any given setup is determined by the terrain between you and the tower site, the tower site profile (how high antennas are, power out, if there is downtilt preventing the signal from going to far from its intended audience). As a general rule I can usually stand outside with an 800 ducky on a scanner and pull in tower sites 20+ miles away, all dependent upon my location.

More importantly you want to hope you aren't too CLOSE to an 800 mhz transmitter. If you are, it'll overload the receiver and you'll have to set the gain down low, which will result in you possibly not being able to pull in some further away stuff that you normally would be able to pull in if you were able to turn the gain up. A lot of it is just trial and error testing.

 

[maus92]

Great info. Just curious what antenna you are using? Also is there a max distance in miles you can be away from a tower site? For example, I’m about 10 miles away from the Nicollet tower I’m pulling from but the Janesville tower is about 15-20 miles away that I’m wanting to connect to next.

A lot depends on your receive antenna situation, and the height (AGL) and directionality of the transmit antenna(s) - and any interfering terrain, structures, or RF.