SDRTrunk Can't adjust control channel frequency

wbswetnam

Member
Premium Subscriber
Joined
Oct 11, 2005
Messages
1,752
Location
DMR-istan
I've been having trouble with an imported file from RRDB into SDR Trunk. The control frequency should be 769.6875, but SDR Trunk insists on tuning to 769.6625 instead. I've tried going to the playlist editor and changing the frequency, but when I hit 'Play", it changes right back to 769.6625. How do I force SDR Trunk to tune to the proper control channel frequency?
(see images below)
 

Attachments

Reconrider

Trx-1 or Sds100
Feed Provider
Joined
Sep 26, 2017
Messages
1,008
Location
CT
I did the same thing.

Don't do it that way. Tuning to a frequency is crap on sdrtrunk.
Import the system from the Radio Reference tab. https://prnt.sc/1rtkyae

Login at the top right,
set your country, state, county.
Click System under the county trunked systems
Click System view tab under the system you choose

Click the site you want to follow
On the bottom right, give everything a name so you know who it is.
Click NEW ALIAS LIST and give that a name - this is where all your talkgroups will be in.

After you do that, click Create Channel Config
---

You're gunna have to go back to the RR tab and click TALKGROUPs tab now. You need to import them so you know who they are

I would suggest leaving "mute encrpyted talkgroups" checked. No reason to have it unchecked unless you want to hear the static and blippings.

After you click Import, go back to the channels tab up at the top left.

click start/play


if i forgot something or you need more help, just quote me
 

wbswetnam

Member
Premium Subscriber
Joined
Oct 11, 2005
Messages
1,752
Location
DMR-istan
if i forgot something or you need more help, just quote me
I tried reimporting from the RRDB. In the editor it shows the control channel correctly, i.e. 769.6875. But when I press PLAY and look back at the waterfall display, again it's tuned to 769.6625! It's off by 250 KHz. I tried using a different RTL-SDR dongle (an RTL2832U), but with same result. See images in my original post.
I'm stumped.
 

lwvmobile

Member
Joined
Apr 26, 2020
Messages
231
Location
Lafayette County, FL
Just something to keep in mind, SDRTrunk isn't going to park the tuner directly on the center of the frequency you are tuning. There will be a slight offset from what the center is and what frequency you are locked onto. If you have voice channels open up close to the control channel, you'll see SDRTrunk adjust that center frequency to attempt to pick up additional voice channels if you don't have enough free tuners to cover everything. I've seen where the CC can be near center then a voice channel open up and SDRTrunk adjust so the CC is far left of the waterfall and a voice channel be on the right side. Its pretty dynamic on what frequency it actually tunes, the important thing is what frequency gets locked on to in the 2.4Mhz it has to play with on a RTL2832.

Also, SDRTrunk 'SHOULD' try to correct that signal lock by adjusting the PPM, but sometimes it takes a moment for it to start adjusting, you should see a Measured Error if its off a slight bit.
 
Top