BCD436HP/BCD536HP: PT0 PT1
- Thread starter dubir
- Start date
- Status
Those indicate P25 Phase II. Many people have found that Phase II audio doesn't sound as good which makes sense since they are only using half the audio data as a Phase I transmission. Half the data means you have half the resolution for the audio.
I've never heard any Phase II systems on Motorola radios or scanners yet, so I can't speak of the difference first hand other than the above fact.
I've never heard any Phase II systems on Motorola radios or scanners yet, so I can't speak of the difference first hand other than the above fact.
WA0CBW
Member
I believe they are using the same amount of data it is just in time slot 1 or time slot 2.
BB
BB
Not sure if that was a reply to my post or not.
I believe all P25 channels use 9600.
In the case of Phase I audio and ALL control channels, that is available 100% of the time.
In the case of Phase II audio, it's only available 50% of the time due to the two timeslots, so you end up with half of the data you would for a Phase I audio transmission. Trying to convey the same information (or information type) using half the data will result in less resolution, hence added artifacts.
I believe all P25 channels use 9600.
In the case of Phase I audio and ALL control channels, that is available 100% of the time.
In the case of Phase II audio, it's only available 50% of the time due to the two timeslots, so you end up with half of the data you would for a Phase I audio transmission. Trying to convey the same information (or information type) using half the data will result in less resolution, hence added artifacts.
P25 P2 voice channels use 12kbs/ps .
OK, but that still means only an effective 6kbs/ps per slot as opposed to 9.6kbs/ps (using the terms you used) which results in a lower resolution.
I thought all P25 used 9.6k. But, that explains why Phase I scanners cannot support Phase II...
I thought all P25 used 9.6k. But, that explains why Phase I scanners cannot support Phase II...
troymail
Silent Key
When you get good reception and decoding of Phase 2, I don't detect a significant noticeable difference over Phase 1. The issue still continues to be (in my opinion) digital simulcast issues - doesn't matter what radio you have. This issue seems to affect Phase 2 more than Phase 1 P25.
My best and clearest reception/audio (99% of the time) is using a GRE/Whistler that is placed in a fixed location. I actually have two radios in two different locations monitoring two different sites of my state Phase 2 system.
My best and clearest reception/audio (99% of the time) is using a GRE/Whistler that is placed in a fixed location. I actually have two radios in two different locations monitoring two different sites of my state Phase 2 system.
Hello,
P25 Phase 1 is a 7200 bps IMBE vocoder using 4400 bps voice and 2800 bps error correction.
P25 Phase 2 is a 3600 bps AMBE+2 vocoder using 2450 bps voice and 1150 bps error correction.
You can not compare the two directly via bit rates as the AMBE+2 vocoder encodes voice at lower rates better. There are less bits percentage-wise dedicated to the error correction for Phase 2, so voice quality may degrade faster as signals get weaker. Error correction is only used for the important bits, so voices sound more robotic on weak signals.
73 Eric
P25 Phase 1 is a 7200 bps IMBE vocoder using 4400 bps voice and 2800 bps error correction.
P25 Phase 2 is a 3600 bps AMBE+2 vocoder using 2450 bps voice and 1150 bps error correction.
You can not compare the two directly via bit rates as the AMBE+2 vocoder encodes voice at lower rates better. There are less bits percentage-wise dedicated to the error correction for Phase 2, so voice quality may degrade faster as signals get weaker. Error correction is only used for the important bits, so voices sound more robotic on weak signals.
73 Eric
Hello,
It is per slot.
73 Eric
It is per slot.
73 Eric
W8RMH
Feed Provider Since 2012
- Joined
- Jan 4, 2009
- Messages
- 8,109
- Reaction score
- 200
I have seen some videos here of Phase II reception and it doesn't sound any different than Phase I.
Phase II digital sounds more like TRBO than Phase I digital.
OK. So Phase II is using half the overall data rate for voice data and less than half of the Error Correction.
Suffices to say it will likely never sound as good as Phase I.
SOFA_KING
Member
Thank you very much, Eric, for giving us true accurate information instead of some pretend know-it-all who knows nothing and can't keep their mouth shut.
The truly sad part about all the disinformation this person spouts off about on nearly every thread is that unsuspecting people who are looking for accurate information get the wrong idea and misled by this person that doesn't know when to shut up. And this person always tries to spin and pivot out of admitting they are wrong. This is damaging to the reputation of this forum. People come here for good answers, not pseudoscience or some self-proclaimed expert rubbish. It tarnishes the forum.
As to the OP's question, you can improve some performance by setting the P25 Threshold to MANUAL instead of AUTO. You have to create a Favorite List of the system in question to be able to change it to MANUAL. The full database doesn't allow manual, so copy what you want to a new favorite list if you haven't already done so. Then you can edit the FL and force it to manual. I find a value of 10 works good on 800 MHz, but other values may be better. This helps the P25 decode optimize for best reception. It may even help on simulcast systems, although those can be very distorted and hard to receive. It helps on one of mine that otherwise I would get nothing but broken bits and pieces. I also find a value of 9 works for my VHF and UHF. Experiment and see if you can find sweet spot.
Hope that helps.
Phil
Don't get CODEC processing confused with radio data rate. P25 systems, as I understand it and have read many times, transmit at 9600 over the air. The CODEC may use less of a data rate. It's not unlike using a 25 MBPS internet connection to transfer a file as 8 MBPS. That doesn't mean the internet connection is only 8 MBPS.
I made no prior claims about the CODEC rate, so your assumptions about my being wrong were in and of themselves wrong. Ironic, ain't it? You're guilty of what you claim others are. But, that often happens with people who post in anger.
I made no prior claims about the CODEC rate, so your assumptions about my being wrong were in and of themselves wrong. Ironic, ain't it? You're guilty of what you claim others are. But, that often happens with people who post in anger.
SOFA_KING
Member
Denial. :roll:
Meantime nothing you said did anything to assist the OP.
Pathetic!
Meantime nothing you said did anything to assist the OP.
Pathetic!
Every post I made in this thread deals with the OP's issue except for the one in which I pointed out the error of your post that criticizes me. Even that post has information that is marginally relevant, as I point out the technicalities of P25 which you failed to grasp - specifically that CODEC rate and Radio Data rate are not necessarily the same thing.
Now please get over your attitude and stop trying to create division where none exists. THAT is what is pathetic. What I posted does not contradict what Eric posted. And what he posted does not contradict what I posted. We were talking about two different, but related, things.
Pointing out that they are different things is not denial. But, thanks for the laugh.
Stop trying to pick fights. I'm not going to fall into that trap. If anything, it's only making me feel sorry for you.
Now please get over your attitude and stop trying to create division where none exists. THAT is what is pathetic. What I posted does not contradict what Eric posted. And what he posted does not contradict what I posted. We were talking about two different, but related, things.
Pointing out that they are different things is not denial. But, thanks for the laugh.
Stop trying to pick fights. I'm not going to fall into that trap. If anything, it's only making me feel sorry for you.
Perhaps we can focus on the OP's question rather than bickering?
- Status
