Hello everyone, I was wondering if anybody would know why sometimes when I'm using my 2 RTL-SDRs to listen to a P25 system it will pick up all transmissions, but then randomly it will miss one. Does anyone know how to fix this?
SDRTrunk SDRTrunk RTL-SDR skipping over P25 transmissions
What system? What site? Does the range of frequencies on the site fit within the bandwidth of 2 rtl-sdr’s? If the frequency spread (the difference between the highest and lowest site frequency) is greater than ~4.8 MHz, you will need more than 2 RTL-SDRs to reliably cover the system. Each RTL-SDR covers ~2.4Mhz. You will miss transmissions on voice frequencies that fall outside the 4.8MHz range. This is one possibility. If this is the issue, you should get messages of ”Error starting channel [xxxx] No Tuner Available”
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Albany/Schenectady Counties P25 System, County Cell which is a 2.8 mhz spacing. 2 RTL-SDRs are more then enough. I am not getting any no tuner available messages, it'll say the normal "Phase 1 channel grant PRI4 circuit".
How many traffic channels do you have set for Max Traffic Channels?
I have it set to 10.
Which site are you using?
| RFSS | Site | Name | County | Freqs | ||||||
|---|---|---|---|---|---|---|---|---|---|---|
| 1 (1) | 001 (1) | Albany Metro Simulcast | Albany | 851.2625 | 852.575 | 853.3625 | 855.4625 | 855.7125 | 856.1125c | 856.2625 |
| 856.4375 | 857.2125 | 857.2625 | 857.4375 | 858.2625 | 858.4375 | 858.9375 | ||||
| 859.2625c | 859.4375 | 859.7125c | 860.2625c | |||||||
| 1 (1) | 002 (2) | Albany County Simulcast | Albany | 851.7375 | 852.1875 | 852.950c | 853.7375c | 854.0375c | 854.5375c | |
| 1 (1) | 003 (3) | Cohoes | Albany | 858.2125 | 859.2125 | 859.9375c | 860.4375c | |||
| 1 (1) | 004 (4) | Schenectady County Simulcast | Schenectady | 851.2875c | 851.850c | 852.075c | 852.350 |
Albany County Simulcast..
So 2.8 and your using 2 rtl dongles. What are their sample rates set at in the tuner tab?
They’re set at 2.4, I’ve tried lower and that doesn’t work either.
Does the control channel ever show idle in the Now Playing tab? Do you see any sync loss messages?
Nope, never see any of those messages.
Could it just be the program SDRTrunk or is it something with my SDRs? I may just post on the SDRTrunk Google board and see if they have anything more.
How do you know you are actually missing calls? Does it do this on just one system or others too?
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Does this happen all talkgroups - or just one? Multiple voice channels - or just one? Etc.
What is happening on the now playing tab when a call is missed? Any clues here?
I know I’m missing calls because the dispatcher will call a unit then the unit responds and I can’t hear them at all, then, right after that, I’m able to hear the dispatchers response. I only monitor the one system but I know it’s not normal because I’m able to hear every single call on my SDS100.
Happens on all talkgroups, on the playing tab, it shows the blue “Call” tab but the channel alias does not pop up next to the audio output area where it normally does.
You will only hear two tgs maximum at any one time. If more than 2 calls are being processed simultaneously, it's possible you will miss parts of a conversation as the program doesn't try to follow a conversation thread. It sees a channel grant and plays the audio if one of the two audio channels is available. If both audio channels are busy, you won't hear other concurrent tgs / channel grants. You can try unlistening tgs of lower priority, or install Trunking Recorder which queues calls.
dickie757
Wired
Do you hear all 5 calls simultaneously? What is displayed in the left and right channel windows when 5 grants are active? Is 5 channels of audio mixed into 2 audio channels?
1 Rtl-sdr stick might cover your system but the OP needs 2 sticks as the cell he is listening to spans 2.8MHz.
Sdrtrunk only has left and right channel, which lets you "listen" to only 2 tg's simultaneously. The OP has not mentioned if he is using TR or Rdio Scanner, which would let one record multiple tag’s simultaneously.
Could be a signal issue. Could you post screenshots of the spectrum for both dongles?
Already stated I have 2 which is plenty.
I do not use TR or Rdio Scanner but SDRTrunk will play each transmission back to back. Say local PD and EMS are talking at the same time, it will live play the PD call then as soon as the PD call is over then it will switch over to EMS and also play what I missed while listening to PD.
I’ll post screenshots later, but signal is definitely not a problem. I’m well within coverage of my system and receive perfect reception on all other transmissions. If it helps my SDS100 averages an RSSI around -85dbm.
