mototrbo digital

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johnny1225
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mototrbo digital

Post by johnny1225 »

I have a question on Mototrbo going from analoge to digital. I have 3 Hospitals that were using a Mototrbo XPR8300 Repeater c/w XPR6350 Portables in UHF Band. I would say that all 3 Hosptials were getting about 95% coverage. I switch them to digital about 2 weeks ago and there coverage in all 3 hospitals have dramtically dropped in coverage. I thought that digital dramatically increased coverage not reduced it that much. They are very unhappy with the digital results. My question is , is there anything i can do to improve there coverage back to were it was in the analoge format without running more antennas and cabling or is there a antenna or cabling that i should be using in the digital format. We are using 1/2" foam heliax cabling from andrews. Any replies would be appreciated.

Regards,


John
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Bill_G
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Re: mototrbo digital

Post by Bill_G »

That's the opposite of my experience. However, it does take some time to get used to the audio - the absolute emptiness behind the voice. No hiss, no crackle, and every word sounds mushy. There was some howling from several people about the Trbo audio quality. One customer switched back to analog because of all the complaining by his crew. Analog - they were happy. Digital - they were unhappy. And according to the guys working on it, all the gear checks out okay. There were some issues with mic gain set too high. But even after fiddling with that, the customer pulled the plug and went back to analog. It may not be a range issue at all, but a quality problem.
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Tinker'r
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Re: mototrbo digital

Post by Tinker'r »

Make sure you are running Firmware Version R01.07.00 (or later) in your repeater and subscriber units. This is also the 1st time that I've heard of DMR offering less range than that of Analog. Are you sure that the repeaters output power didn't get bumped while configuring it for digital?
johnny1225
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Re: mototrbo digital

Post by johnny1225 »

I know what you mean about the audio in digital it took about the full two weeks to get them use to it. I am quite sure it is a range problem because where they could get coverage before now it does the bonking noise when you press the PTT. If i switch everything back to analoge they will get those areas again. Is there any other Repeater settings that is a must to enable or disable when switching to digital? Is there any other suggestings.

Thanks

John
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wavetar
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Re: mototrbo digital

Post by wavetar »

Are these repeaters running 'standalone' or in an IP Site Connect configuration? What do you have the subscriber units set for admit & in-call criteria?

What are you using for duplexer or other filtering? Just because things worked 'ok' in analog does not mean the filtering was optimized...slight desense hurts you a lot more in digital than in analog (drives the BER up).

Todd
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johnny1225
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Re: mototrbo digital

Post by johnny1225 »

All 3 hospitals are standalone are not in ip site connect. 2 of the hospitals are digital and 1 of the hospitals is using capacity plus. In capacity plus the admit criteria is set to channel free and in call criteria is set to follow admit criteria. The other 2 hospitals that is digital is set to always. There are no filtering cans we have taken then out of the system. The duplexer we are using is a brand new Q3220 duplexer from sinclair labs. What do you think?

Regards,


John
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escomm
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Re: mototrbo digital

Post by escomm »

Are the frequencies shared use? Have you gotten a spectrum analyzer out to look for birdies? I'm sure with all that medical equipment there you will find many. Why not use an admit criteria for digital of always? The subscribers will still not key up on digital if they can't find the repeater for timeslot reference.
RFguy
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Re: mototrbo digital

Post by RFguy »

johnny1225 wrote:There are no filtering cans we have taken then out of the system. The duplexer we are using is a brand new Q3220 duplexer from sinclair labs. What do you think?
Major clue here.

So more that the repeater was changed. Did the frequency stay the same? Did the antenna stay the same? Jumpers? Power levels?

Has the new duplexer performance been confirmed against the manufacturers specs? (Insertion loss and isolation tests)
What is the site noise and desense figures?

If the frequency is the same, what happens when you put the old "filters" in?

What was the configuration of the old multi-coupling system? Do you do from a band-pass type (providing off frequency protection)? The new Q3220 is an OK duplexer, but far from high spec. The Q3330E is a higher spec unit if the are any adjacent frequencies.

Are there other frequencies on site? If so, what is the TX to RX isolation? What is the TX sideband noise like from any adjacent TX.
ard099
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Re: mototrbo digital

Post by ard099 »

I'll agree with wavetar and say you need to check your admit criteria and in call criteria. If you have it programmed for "channel free" and you have some interference in certain areas that exceed the threshold you may run into problems like that. Try setting it to "always" or "color code free" and see if that helps. Every Trbo system I have been around has far exceeded coverage compared to analog.
Ali Abbassi
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Re: mototrbo digital

Post by Ali Abbassi »

Coverage of a TDMA digital radio system will always be smaller as compare to analog FM system assuming everything else are the same, it is the higher SNR required for TDMA demodulator that causes the coverage to shrink, FM narrow band signal that is 5 dB above the noise can be demodulated and produce a fairly good audio, but for a TDMA (4 level PSK Mototrbo) you would need to be at least 8 dB above the noise for 5% BER.
JRayfield
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Re: mototrbo digital

Post by JRayfield »

This is not true with MOTOTRBO. MOTOTRBO systems consistently provide more range as compared to analog fm, especially narrowband analog fm. This has been proven in 'live' systems, and I've discussed this with numerous engineers at Motorola and they all agree that MOTOTRBO will usually provide better range than analog FM.

John Rayfield, Jr. CETma
Rayfield Communications
Ali Abbassi wrote:Coverage of a TDMA digital radio system will always be smaller as compare to analog FM system assuming everything else are the same, it is the higher SNR required for TDMA demodulator that causes the coverage to shrink, FM narrow band signal that is 5 dB above the noise can be demodulated and produce a fairly good audio, but for a TDMA (4 level PSK Mototrbo) you would need to be at least 8 dB above the noise for 5% BER.
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xmo
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Re: mototrbo digital

Post by xmo »

"This is not true with MOTOTRBO."

----------------------------------------------------------------------------------------------------------------------------------------------

Agreed.

Mototrbo at a static 5% BER signal level produces a Delivered Audio Quality [DAQ] comparable to 12 dB SINAD in an analog system. [definition of reference sensitivity]

ETSI DMR 2 slot TDMA, AMBE+2, 12.5 kHz [Mototrbo] requires 5.3 dB C/N to deliver 5% BER whereas analog FM +/-2.5 kHz, 12.5 kHz requires 7 dB C/N to deliver 12 dB SINAD. This is equivalent to DAQ 2.0.

Most systems are designed and tested to deliver better audio quality targets such as DAQ 3.0 [or higher].

Comparison of the real world, on-the-street, faded signal performance of the two formats shows an even greater advantage for Mototrbo. Narrowband analog FM requires 23 dB C/(I+N) to deliver DAQ 3.0 whereas ETSI DMR requires only 14.3 dB C/(I+N).

That substantial difference of 8.7 dB is the reason why, as JRayfield says: "MOTOTRBO systems consistently provide more range as compared to analog fm, especially narrowband analog fm."

These facts have been developed through extensive research which has been published by the Telecommunications Industry Association as TSB-88.

TSB-88 is used by engineers to design systems and to develop the software, tools, and procedures used for coverage acceptance testing. Many system RFP documents reference TSB-88 in order to ensure that responding vendors Coverage Acceptance Test Plans [CATPs] are comparable and incorporate the latest knowledge.
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escomm
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Re: mototrbo digital

Post by escomm »

TSB88 is a mathematical model and while relied upon by the FCC for interference studies is not an exact real world equivalent as much as the engineers that wrote it (and make royalties off it) would have you believe, probably just the closest anyone will ever get to real world equivalence though. Have seen more than a handful of 470+ licenses rescinded because the TSB-88 study showed 5%+ of expected contour degradation but the incumbent challenging the issuance of the license could not ever provide recordings or signal readings or other hard evidence of interference. No matter, TSB-88 is the bible when it comes to this and if 5.000000000000000001% degradation is present the license is rescinded. Saw one where TSB-88 showed a degradation of 25% but the field study didn't agree.

Still, though, the rules are the rules, and as best I know the rules rely on TSB-88 as the arbiter for calculated interference
Ali Abbassi
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Re: mototrbo digital

Post by Ali Abbassi »

Mototrbo brochures has a comparison graph that shows the analog radio continues to provide coverage on the fringe area , Mototrbo would provide uniform audio quality to a point where SNR is of a sufficient magnitude for error free decoding of the digital signal , beyond that point audio quality suddenly drops while analog radio continues to provide readable audio for some distance beyond that point., this fact is because of higher SNR required for QPKS digital modulation as compare to FM analog modulation .
ard099
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Re: mototrbo digital

Post by ard099 »

Well Im not gonna disagree with you about what the chart states from Motorola, you are correct about what it says on paper. In the real world, Mototrbo flat out, no doubt about it, absolutely, outperforms analog systems in a side by side comparison- at least in my trials. I understand each situation is unique but If someone has a system with the same specs and they have better coverage in analog then mototrbo I'd be curious to see that system.
Ali Abbassi
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Re: mototrbo digital

Post by Ali Abbassi »

In general more complex modulation would requires higher SNR at the input to the decoder section of the receiver to produce the same BER, which in turn reduces the range if all other factors remains the same. In most situations the Mototrbo signal within the operating area is higher than the required level to produce DAQ.4, and you will have consistent and uniform audio over the entire area of operation, the difference will be experienced when, you are at a distance that DAQ is 3.5 and the receiver is moving away form the site from that point very rapidly the DAQ is going down to 3, which is not acceptable quality by a Mototrbo radio user, this is the point where the SNR is below the level to produce BER<10-5 , the Mototrbo coverage ends there ,but a 12.5 kHz FM analog radio system under the same condition will provide usable coverage( with some background noise but understandable audio) beyond that point , in actual field condition the Mototrbo max usable coverage is about 90% of the equivalent 12.5 FM analog system
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xmo
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Re: mototrbo digital

Post by xmo »

I don't know how you came up with that analysis - you didn't cite a source, but numbers without foundation based on a credible source are meaningless.

If you came up with that by drawing lines on one of those digital vs. analog charts that the marketing guys provide - that won't work - they are only approximations.

In fact, the only credible source for land mobile is TSB-88 which is THE industry's published knowledge base and which is tied directly to industry standards for performance and equipment verification such as ANSI/TIA-603 for FM and ANSI/TIA-102 for P25 digital.

As previously stated, the FACTS are that ETSI-DMR format has an 8.7 dB advantage over 12.5 kHz analog at DAQ 3.0 and will provide an accordingly larger area of satisfactory communication.
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Wowbagger
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Re: mototrbo digital

Post by Wowbagger »

I think the key here is the phrase "but a 12.5 kHz FM analog radio system under the same condition will provide usable coverage( with some background noise but understandable audio)"

"understandable audio" means different things to different people. To TSB-88, it's a signal that is clean enough to copy without a great deal of effort - a signal you can understand while fighting a fire, or a firefight, or stabilizing a patient.

To many "radio operators", it means "repeat it a few times, slowly and distinctly, and I will copy most of it" (hence the plethora of "59" reports, after asking for five or six repeats....)
This is my opinion, not Aeroflex's.

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Jim1348
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Mototrbo Digital

Post by Jim1348 »

From my personal experience, P25 sounds better to my ear than MOTO TRBO. I suppose that is like comparing apples to oranges, but just saying that has been my personal experience.
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xmo
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Re: mototrbo digital

Post by xmo »

That is another interesting subject for discussion - audio quality comparison between VOCODERs - IMBE vs. AMBE+2 and comparison between various products - manufacturers and models.

According to DVSI tests, the newer VOCODER scores a little higher than IMBE - but individual assessments may vary.

The whole DAQ thing is based on a subjective scale. Originally the only way to arrive at a DAQ score for a specific product or system was to use a large group of people as evaluators. Now there are computerized audio quality evaluation systems that use algorithms such as PAMS, PSQM, and PESQ. Several test equipment vendors offer products incorporating these methods - some of these products are even targeted to evaluation of audio quality in P25 systems.

For those interested in learning more, the Institute for Telecommunication Sciences (ITS) in Boulder, Co. has done extensive research into public safety audio quality.
JRayfield
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Re: mototrbo digital

Post by JRayfield »

Your statement "In general more complex modulation would requires higher SNR at the input to the decoder section of the receiver to produce the same BER" is interesting. Maybe MOTOTRBO hardware and firmware works better than "In general". Unless you work for Motorola, in engineering, on the MOTOTRBO product line, you have NO idea about how they've specifically implemented hardware/firmware in the MOTOTRBO radios/repeaters. All you can speak of is "In general".

Based on personal experience with MOTOTRBO vs. analog FM (wide and narrow), with several different systems (UHF and VHF), as well as conversations with engineers at Motorola and at Radiosoft, your statement that "in actual field condition the Mototrbo max usable coverage is about 90% of the equivalent 12.5 FM analog system", simply doesn't "hold water". It's that simple. If you have some kind of documentation (i.e. proof) of this statement, I would be very interested in seeing it and providing it to Motorola engineers (I know that they'd be interested in seeing any such documentation).

John Rayfield, Jr. CETma
W0PM
www.rayfield.net

Ali Abbassi wrote:In general more complex modulation would requires higher SNR at the input to the decoder section of the receiver to produce the same BER, which in turn reduces the range if all other factors remains the same. In most situations the Mototrbo signal within the operating area is higher than the required level to produce DAQ.4, and you will have consistent and uniform audio over the entire area of operation, the difference will be experienced when, you are at a distance that DAQ is 3.5 and the receiver is moving away form the site from that point very rapidly the DAQ is going down to 3, which is not acceptable quality by a Mototrbo radio user, this is the point where the SNR is below the level to produce BER<10-5 , the Mototrbo coverage ends there ,but a 12.5 kHz FM analog radio system under the same condition will provide usable coverage( with some background noise but understandable audio) beyond that point , in actual field condition the Mototrbo max usable coverage is about 90% of the equivalent 12.5 FM analog system
Rayfield Communications
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JRayfield
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Re: mototrbo digital

Post by JRayfield »

I'm not sure where you go your 'graph' from, because the one that I have from Motorola clearly shows better performance of MOTOTRBO over analog FM. I would very much be interested in seeing this graph that you speak of.

John Rayfield, Jr. CETma
W0PM
www.rayfield.net
Ali Abbassi wrote:Mototrbo brochures has a comparison graph that shows the analog radio continues to provide coverage on the fringe area , Mototrbo would provide uniform audio quality to a point where SNR is of a sufficient magnitude for error free decoding of the digital signal , beyond that point audio quality suddenly drops while analog radio continues to provide readable audio for some distance beyond that point., this fact is because of higher SNR required for QPKS digital modulation as compare to FM analog modulation .
Rayfield Communications
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www.rayfield.net
com501
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Re: mototrbo digital

Post by com501 »

Two 12 slot trunking systems, co-located with an additional 5 conventional Trbo repeaters plus 8 narrowband analog Trbo repeaters. 2000 handhelds operating in an absolutely flat environment (plus/minus 1 foot in elevation),. radius of operation 13 miles (RADIUS), digital flat out-performed analog every single time. Every radio, identical Trbo handhelds, novice to pro operators, for an extreme operation period of 2 weeks. Tower is 70 feet, co-located at the site of the event.

Its called BurningMan, and we do it every year. This was the first year of Trbo implementation, and far exceeded our expectations over analog from the past 15 years.
Ali Abbassi
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Re: mototrbo digital

Post by Ali Abbassi »

For mathematical explanation of Minimum Detectable Signal of various modulations .
https://ccnet.stanford.edu/cgi-bin/cour ... 7378245639
http://www.ittc.ku.edu/~jstiles/622/han ... Signal.pdf
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