Ah - ok. Good to know (but sorry to hear that). Given that everything coming out the IF ought to be the same regardless of the band being monitored, I can't for the life of me figure out why this would be an issue on UHF and not 700/800 MHz. UNLESS - UHF doesn't throw some switch in the firmware that the others do (bandwidth, maybe?). Very frustrating...
HELP! P25 Phase 2 Reception Problems
- Thread starter Donradtke
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Ah - ok. Good to know (but sorry to hear that). Given that everything coming out the IF ought to be the same regardless of the band being monitored, I can't for the life of me figure out why this would be an issue on UHF and not 700/800 MHz. UNLESS - UHF doesn't throw some switch in the firmware that the others do (bandwidth, maybe?). Very frustrating...
I think the biggest info that nobody is providing when they try different settings (especially turning on/off Attenuation) is the signal strength indication! AS we know these radios have strong signal issues and if the signal that is in question is showing 5 bars and turning on ATT and its still 5 bars then the incoming signal is still TOO strong. In this case if your using an outside antenna, try the rubber duck. If the signal is STILL at 5 bars then take the antenna off and try it.
Signal strength indication before and after setting changes is a very important part of trying to solve reception/decoding issues.
Well, in my case, that's easy enough to do...
I monitor over a 35 mile commute, across three distinct topographical regions, two to three different UHF nodes (none of which are simulcast) and two to three different 700 Mhz systems - the behavior is absolutely independent of signal strength, shadowing, reflection and relative motion.
It is down to being either a common flaw in the UHF sites (the fact that some, presumably using Unidens or commercial gear, report no problems likely rules this out) or a systematic problem with the Whistler/GRE radios...
One of the things you need to be aware of .. 5 bars is NOT a strong signal.
I tested several scanners .. and 5 bars is not that strong. The reason .. the manufacturers want you to think that the signal is strong and the scanner is working wonderfully. I just want to put this into perspective as it may help with this issue to understand how these scanners work when it comes to the RSSI.
You can read about it here .. http://forums.radioreference.com/ge...4327-what-those-scanner-bars-really-mean.html
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Still having the same issues I posted in post 17. I updated the firmware and my WS1080 does DMR TDMA Con+ flawlessly but the radio will not do P25 phase II TDMA. The radio acts like it's suffering from simulcast distortion but it's definitely not a simulcast site. It doesn't matter the location or antenna. Stationary or mobile it won't do Phase II...period.
Just an idea
Unless it has to do with signal level. For those using an external antenna, and adding ATT doesn't help. Try adding a second external attenuator on the antenna before the scanner. I think the internal attenuator is 20dB, trying making it a total of 30. Get the signal down from a full 5 bars and see what happens.
seth21w
Member
Dsp level 0 ! Adc dac 0, and p25 threshold site hi 99 lo 1 cqpsk
It would be useful to have SDR to get a better idea of the signal characteristics.
Perhaps the signal is too hot. Try attenuation or lowering the ADC gain. The "T" is really on non-stop without any blinking or flashing while decoding the control channel?
Perhaps the signal is too hot. Try attenuation or lowering the ADC gain. The "T" is really on non-stop without any blinking or flashing while decoding the control channel?
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Found a solution to phase II problems. DSP set at default 64, AGC and DAC set to 0db and squelch set at 9 o'clock position or lower. If the squelch knob is rotated past 9 o'clock it will stop on a TG but I won't get any phase 2 audio until I turn the squelch knob back down. Once it gets phase 2 audio I can turn the squelch up and it decodes the rest of the transmission fine but once the next phase 2 transmission starts it has problems again. So I'll leave squelch set low. So phase II doesn't like higher squelch for some reason. Phase 1 transmissions on this site have always been excellent.
Turning the squelch all the way down/open is the # 1 thing to do to achieve better trunked (and simulcast) operation by the consumer scanners. Interestingly, it does not seem that Whistler advocates this; however, I believe the Uniden support does vouch for this method.
This keeps the signal flowing to the DSP instead of the discriminator fluttering the signal on and off.
Of course there are other important considerations, such as programming only one site in the system and only the active control channel in the site.
I wonder if the P25 Phase 2 TDMA vs Phase 1 digital difference has to do with the characteristics of the Phase 2 TDMA modulation and data stream (two time slots.. maybe the scanner doesn't like it when one is empty).
This keeps the signal flowing to the DSP instead of the discriminator fluttering the signal on and off.
Of course there are other important considerations, such as programming only one site in the system and only the active control channel in the site.
I wonder if the P25 Phase 2 TDMA vs Phase 1 digital difference has to do with the characteristics of the Phase 2 TDMA modulation and data stream (two time slots.. maybe the scanner doesn't like it when one is empty).
D
darunimal
Guest
Yes the Squelch should be all but open for almost all situations when it comes to Digital signals, but bad decode has more to do with user adjusting these: the AGC ADC & DAC into the positive, increasing basically makes a signal that should have -1's & +1's, you boost any of those three settings and your dissorting the symbol locations, so in essence: if you increase AGC +1, the -1s become 0's and the +1's become 2's (basic appx to what happens, applying negative numbers make the situation happen the other way). Attenuation is a better solution than changing the squelch, in a users' effort to reduce incoming spurious signals. DSP can be very System specific and user can use steps of 8 to find best receive/decode setting for that system, but the previous set of 3 setting are better left at 0 for Phase 2 systems. In FM signals, increasing any/all of those 3 setting, increases the signal, not so bad for Phase 1 (though as we see maybe 0 would be best for Simulcast Systems), and it's certainly not bad for most systems like Moto Type II or older.
DAC gain has nothing to do with it.
ADC, I agree, should be 0 or below. Three are 4 symbols in the Phase 2 modulation. There is also an amplitude component. The gain does seem to distort the signal. I'm not sure if the way you describe it is accurate, however.
I haven't had much success with DSP modifications on any system. Not sure if it is worth fusing with.
Of course, all of this is foolish, we should be using the correct tool for the job.
ADC, I agree, should be 0 or below. Three are 4 symbols in the Phase 2 modulation. There is also an amplitude component. The gain does seem to distort the signal. I'm not sure if the way you describe it is accurate, however.
I haven't had much success with DSP modifications on any system. Not sure if it is worth fusing with.
Of course, all of this is foolish, we should be using the correct tool for the job.
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