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I just tried one with the same results on my TRX-2
TRX-2: Whistler TRX2 NXDN Problem
- Thread starter anelson5004
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I just tried one with the same results on my TRX-2
Correct..that's because it doesn't accept 3.125 khz frequency entry...yet.
Ubbe
Member
I wouldn't expect a scanner to be that precise without a high stability oscillator that it would matter with a 1.25KHz error. The narrowest filter are probably 12KHz anyway. Even a 3.125KHz error wouldn't matter to the discriminator to induce any distorsion to the demodulated signal. If the error are biggare than that you could always try to use FM (20KHz filter) instead of NFM.
/Ubbe
While I agree with this, the user still should be able to enter the correct center frequency, it's pretty critical at these super narrow bandwidths.
Agreed...this is a changing scanner world yet again. This would be a non-issue if the scanner decoded the NXDN control channel instead of scanning through entered frequencies. I've been sent screen shots of DSD on the NXDN system I monitor and that's probably the issue of missing replies to conversations...the scanner is going to one of the 3.125 khz frequencies that the scanner isn't able to have programmed. If the scanner decoded the NXDN control channel, it would automatically find the proper frequency/talkgroup. This is a step in the right direction, but still needs some tweaking. It has been submitted for future firmware upgrades.
racingfan360
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I did some testing on a TRX1 a few months back.....it suggested the narrowest front end filter was approx 10khz wide (ie +/-5khz of center frequency). So being able to tune within 5khz of the desired frequency is good enough to get a decode: it's one of the key reasons why I asked the OP of this thread to confirm what happens if he tunes +/-5khz of the frequency he's been monitoring, in case the system is running with +/-3.125khz offsets.
None of that takes away the desire to be able to properly tune the TRX to the correct frequency in the first place: I sent my feature request for 3.125khz step sizes back in Feb.
They won't ever have control channel decode for NXDN because the channel number to frequency table is built by the system admin and not hardcoded like the old Motorola systems. So unless you had a way to build a custom table in the scanner and get the freq to channel number relationship correct from using DSD, the scanner won't be able to follow the calls via the control channel.
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Kf4lza: What would cause a conventional NXDN48 system to have full signal bars and no audio? I am connected by an outdoor antenna trying to monitor frequency 155.53500 in VA? There are times that this frequency transmits during the day hearing bits and pieces and sometimes only at night. All other audio on my Whistler TRX2 is great except for this frequency only.
I'm confused. Are you saying that _you_ entered 471.31563 and the scanner rounded it off to 471.31875? If so, that is exactly what it is supposed to do. 471.31875 would be a valid frequency, 471.31563 would not.
From what I can see above, unless you stated it wrong, the scanner has 471.31875, 472.25625 and 472.31875 programmed in it -- and that would be correct.
Mike
From all the reading I did on NXDN, this might be possible if Uniden or Whistler had something similar to LCN search programmed in? If I have all the known frequencies of a NXDN site (including the 3.125 khz) frequencies, program them in and the scanner can sort them properly in the site? The scanner returns to scanning only the control channel of the site, finds the talk group and follows the order of programmed site frequencies similar to LTR systems?
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troymail
Silent Key
Maybe I'm misunderstanding your comment but -- not sure I agree. I think this is what is already done for LTR with "LCN" assignments to the frequencies.... That is, to program properly, you have to know and program all of the frequencies along with their assigned channel channels for that specific system.
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I am having the same trouble with my TRX2 and NXDN vhf frequency. I have the same setup.
Try setting squelch to 10, I am finding that squelch could be related. Also, try with no RAN set, RAN sometimes causes trouble.
I am wondering if a type of encryption is used on certain TX that the TRX2 does not recognize to sound the "busy signal"
Please post any ideas or your settings that fix this.
Ubbe
Member
Only if the datastream from the system include a flag that says "Encrypted" will a scanner know that the transmission is encrypted.
Otherwise a scanner will decode the digital stream and it will sound like digital gibberish.
If some users in the system use end-to-end encryption it will usually not trigger the "encrypt" flag.
/Ubbe
sibbley
Member
Data stream with no voice? I know if I hit on a known control channel, I get full bars and NO audio. As I've seen in my neck of the woods, NXDN control channels don't carry voice traffic.
Ubbe
Member
When I listened to a NXDN channel with a second scanner it sent some sort of information for less than 1/2 sec and then sent idle data carrying the exact same data pattern for 30 sec.
There where no audio decoded from the TRX-2.
Perhaps it was someone keying up to check that they are within coverage or the basestation transmits to check that it have output power to the antenna and the SWR are within specs.
/Ubbe
There where no audio decoded from the TRX-2.
Perhaps it was someone keying up to check that they are within coverage or the basestation transmits to check that it have output power to the antenna and the SWR are within specs.
/Ubbe
that would be GPS updates you are seeing happening on a voice channel. We have the ability to have all the gps data from subscribers be sent over control channel or out through a traffic channel. We do both since you can overwhelm the CC with gps updates from users and can cause slower keyups if there are too many users sending gps data at the same time.
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