Digital vs Analog

[Cowthief]

Hello.

The question should be, what does everybody think about all the problems of late with digital in public service?.
How hard would it be to make a radio that could fall back to analog, automatic, no user input required?.
The next question, what about RSSI, like cellular telephones, power level management on the fly, yes this would require a duplex radio, but, perhaps not that hard, look at the dual band, multi-mode, Digital/Analog STARTAC, it that not a // product.
Yes, this would require some means to disable the duplexer to do talk around, but I think // produced a thing on IMTS called a pulsar, that did talk around and full duplex.
The fact of the matter, there is no legit reason to have this great problem, if the people simply started to work together, this can be resolved.
P.S. one other option could be to produce a dual band radio, say 800MHz on primary, VHF or UHF on secondary, when you key up, it tries 800MHz first, if this fails, it defaults to VHF or UHF, this being under the control of RSSI, all the advantage of digital and or trunking, plus the reliability of simple radio.
There are other ways, lets get the ideas out there, lets start thinking people.

Thank You.

[Salem The Cat]

On 2001-12-25 23:54, Cowthief wrote:
Hello.

The question should be, what does everybody think about all the problems of late with digital in public service?.
How hard would it be to make a radio that could fall back to analog, automatic, no user input required?.
The next question, what about RSSI, like cellular telephones, power level management on the fly, yes this would require a duplex radio, but, perhaps not that hard, look at the dual band, multi-mode, Digital/Analog STARTAC, it that not a // product.
Yes, this would require some means to disable the duplexer to do talk around, but I think // produced a thing on IMTS called a pulsar, that did talk around and full duplex.
The fact of the matter, there is no legit reason to have this great problem, if the people simply started to work together, this can be resolved.
P.S. one other option could be to produce a dual band radio, say 800MHz on primary, VHF or UHF on secondary, when you key up, it tries 800MHz first, if this fails, it defaults to VHF or UHF, this being under the control of RSSI, all the advantage of digital and or trunking, plus the reliability of simple radio.
There are other ways, lets get the ideas out there, lets start thinking people.

Thank You.

What's your point ? The question should be,
"how much misinformed anti digital rhetoric
do we want to keep hearing ?"

Headlines from 'journalists' (who wouldn't
know a duplexer from a tripacer), users who
are clueless, and others not directly (key
word - DIRECTLY) involved with the system
implementation, are hardly what one would
consider "informed" sources.

So let's address your comments:

(a). Astro digital, is designed to improve
audio QUALITY (*not* coverage) in the area
of coverage it's designed to encompass. It
in fact does this very well. If you do an
actual drive test and compare the consistency
of analog audio vs. digital for a given area,
you'll find analog comes out 2nd. However, it
(digital), will exhibit a 'knee' in which the
signal quality will drastically drop once you
reach the limit of coverage area (sort of a
3db drop off point).

(b). Adaptive power control is a feature that
is already present in most Motorola's radios
which have it enabled. It does use RSSI as a
deciding factor. APC is a Motorola "value
add", it's not required by the P-25 standard.

(c). There is no "great problem", other than
a few misinformed journalists (and I despise
the entire species), writing headlines on a
few systems they lack even the most basic
understanding of. The "great problem", are
bureaucrats who spend their career sitting
on their asses behind a desk - doing a lot
of second guessing of the system engineers
and consultants, who are actually doing the
system design. This inevitably leads to the
cut in funding of satellite receiver sites,
or site connectivity trade offs - end result?
POOR COVERAGE....this has nothing to do with
digital vs. analog. A poorly implemented
system is a poorly implemented system, the
core technology is irrelevant.

Connecticut State Police, as someone else
pointed out - almost 98% coverage, no issues
at all - properly designed/implemented from
square one. Michigan State Police, ditto.
Let's not forget the numerous feds who have
already migrated to digital with no problems.
And a Astro system in Canada that I believe
"My .02 cents" chimed in on, same thing, no
complaints.

(d). A dual mode radio is - uncalled for. In
a properly designed/implemented system. You
would have no reason for it. Infrastructure
is a HUGE investment. It's highly impractical
to maintain 2 backbones (and the switching)
for this contingency. We recently dissuaded
a large customer from this type of idea when
they were briefed on the actual numbers to
implement this solution. The actual software
on the radio end to accomplish this, is no
doubt trivial. Infrastructure to support it,
is another story.

There are always 2 sides to every story. Once
the facts are revealed, you'll almost always
discover that digital has nothing to do with
the original issue. It's always one of poor
system design (for a variety of reasons, and
most of the time, it'll be financial trade
offs in implementation). I know of several
small communities that are actually running
Astro systems, and are amazed at how much of
an improvement it is over analog.



<font size=-1>[ This Message was edited by: Salem The Cat on 2001-12-26 07:43 ]</font>

[wavetar]

I originally wrote this in a "Modat" thread a few posts back, since it had strayed off topic to a Motorola/Digital bashing thread. This thread is where it belongs though...read on if you haven't already.

I remember reading in MRT magazine a couple of years ago, I believe it was Kansas City, but I could be wrong. The city wanted to sue Motorola because the newly installed public safety trunking system had major issues with coverage & reliability, forcing them to use their older existing systems. Lots of hoopla at the time. As it turns out, the city had no leg to stand on, as Motorola had delivered exactly what the city ordered. The original quote from Motorola was in excess of $36 million dollars, but the municipal bean counters had a third party (don't know who) engineer the system, with the final price tag around $18-24 million (the numbers are a little fuzzy, I only read the article once). Point being, the city brought their problems upon themselves. I wonder how many other places have done the same?

A point could be made that Motorola should never have sold the system since they KNEW it would not work as needed, but money talks, and they were legally protected.

Motorola engineered a two zone, 68 site, Astro capable, SmartZone Omnilink system here in Nova Scotia. The amount of engineering involved with a project of this scale is absolutely mind boggling. It's difficult if not impossible to comprehend how it all fits together unless you're directly & deeply involved with the infrastructure. In this case, the time was taken, the money was spent, and the system works! There are always detractors & people resistant to change, but the various agencies I've dealt with have been extremely positive about the system. They should be, the portable coverage is better than the old VHF system's mobile coverage was. You get what you pay for, unfortunately, it ain't cheap!
My two cents...

Todd

[wavetar]

Just something else to add:

Anybody here ever heard of "Factware"? It's a special hardware/software setup that Motorola uses when designing/implementing a system. Essentially, a laptop is interfaced to either a Spectra or an MCS2000 mobile using a "suitcase" type module. In our case at least, the radios, although new, had to be receiver spec'd with a Motorola R-2670 analyzer, which had to be within it's calibration due date. Basically, once it's all set-up, Motorola will have a Quantar or similar repeater at a site, putting out control channel data at the same power level expected to be used when the system is fully up & running. They then drive the vehicle set-up with the Factware on every single road surrounding the site. The software charts the RSSI on a graph , and as long as it stays above a known minimum value, the signal is considered good. This is painstaking work, not to mention expensive as you're paying a bunch of Motorola employees to do this. It took weeks, if not months to do this with 4-6 vehicles driving around our province checking out all 68 sites. And...THEY DID IT TWICE! Once in the winter, and once more in the late spring, when the foilage was in full bloom, just to make sure to coverage patterns remained unaffected. With this information, coverage maps can be extrapolated before the system is even in place. How many cities/counties have skipped this expensive, time consuming, yet critical step, using third party (read-inexpensive or even cheap) system designers?
I believe the system owner (in our case, the local Telco) signs something which states they accept the fact that RF coverage can only be guaranteed as 95% reliable, any unforeseen holes in the coverage are the customer's responsibility to have corrected, out of their own pockets, not Mototola's. Thus the reason I think the Conneticut State Police will eventually have to pony up the monies to fill in the extra 2% coverage themselves. Life, especially in the RF world, isn't perfect.

Todd

[RFdude]

Wavetar, or others... Your description of "Factware" isn't what I heard...we could be talking about different things altogether. I will repost this question in the Astro group...

The problem with Motorola's approach to SmartZone is that they don't offer any tool to let the system designer understand and SEE how the radio selects and affiliates with a site. Cellular is full of tools that do exactly this...and cell standards exactly describe how the radio selects a site in AMPS for instance... we are talking numbers and technical terms. The only documents I've ever seen from Motorola describe the selection/affiliation process using plain english... such as "the radio selects the strongest signal" instead of using dB... so word was that Motorola had software and a connection to an Astro Spectra that would allow you to drive around and watch what the radio sees, adjacent control channel list, hex RSSI values, and it's decisions, etc. Last I heard was that this was not being made public. Not good. After working in cellular for many years, I don't feel good not knowing what goes on inside of that radio's mind. There are also the hex RSSI thresholds that can be modified to change the radio performance... again.. no real insight from M, just the usual "don't touch it". When pressed, you can't find anyone that can discuss this with any detail.

So what do we do? Confirm coverage predictions with drive testing...as Wavetar described... but using any measurement receiver... like a Grayson for instance. Results plotted against the computed model for verification. Then hope that the radio switches sites like it's supposed to based on RSSI.

Any other info on the MOTOROLA ASTRO SPECTRA interface out there? Please, we need this tool! Especially where there are hybrid systems with portables and mobiles.

Regarding ANALOG vs Digital... I'd like to hear some $ numbers from others... if you are talking in the thousands of mobiles, going digital ONLY is very expensive. Life would be good, but expensive. It seems cheaper to pay the extra for the dual mode and have the cheap ANALOG only in the dog catcher van or snow plow. There doesn't seem to be an entry level SmartZone digital mobile out there.

RFDude.

[Cowthief]

Hello.

I have found that digital does a very good job with voice quality, fair job a coverage, the point of the post is, if someone produced a radio that works BOTH digital and analog, if dual band, so much the better.
Remember PAC/RT, perhaps something along that line might work, sort of a "talk-around".
Yes, if the system has a zillion sites, coverage is great.
The point is, most government use a very tall building if they own it, like the world trade center, redundant, 2 buildings remember, nothing can happen, right?.

Thank You.

[raymond345]

Well a Happy New Year from Canada

My two pennies.We are fed up with high prices and no 100% coverage also.We now have
$1700.00 Ca. dollars for the back-up we need per vech/or person.Sat phone 100% coverage.
$35.00 Can. per mon. and $1.62 Can/minute.
It is worth my peace of mine.This is a hand
held sat.-phone.Greaaaat.

[alex]

Just don't go in to the basement....

[wavetar]

On 2001-12-29 19:33, Cowthief wrote:
Hello.

I have found that digital does a very good job with voice quality, fair job a coverage, the point of the post is, if someone produced a radio that works BOTH digital and analog, if dual band, so much the better.
Remember PAC/RT, perhaps something along that line might work, sort of a "talk-around".
Yes, if the system has a zillion sites, coverage is great.
The point is, most government use a very tall building if they own it, like the world trade center, redundant, 2 buildings remember, nothing can happen, right?.

Thank You.

EVERY Astro radio is already capable of both digital & analog, including the precious Astro Saber & Spectra. Talk-around is certainly easily avaiable, it's a training issue & most users appear to be very stupid. A zillion sites?? Whatever it takes to work with the proper engineering, my friend (150 sites to cover Manitoba is the most I've heard of). The new XTS5000 is 700/800 (dual band) capable. Your remark about redundancy, although laughable just a few months ago, is now nothing but sickening. I guess the joke's on us.

Todd

[Josh]

I have found that digital does a very good job with voice quality, fair job a coverage,

Yes, if the system has a zillion sites, coverage is great.

First, is it not true that when a digital signal does not come in full and strong into the receiver, the reciever acts as if it is not there at all? Whereas in the same situation an analog radio even though broken up a little would still come through, usually comprehendable?

Second, isn't the point of an expensive radio system to have as few towers as possible, yet still get good coverage by well planned radio tower locations?

-Josh

[RFdude]

As the RF signal diminishes, the audio gets mumbled, there are digital artifacts, slurred speech. It is a rapid decline, much quicker than analog. To summarize, you get Q5 audio longer than analog... a noisy analog transmission could be perfect in digital.

Some say that the digital radios gain an extra 6 dB in coverage... that is debatable... we have found it works in some locations where analog doesn't. Certainly the SmartZone control channel can be decoded into the mud. Control channels are often reduced in power for this reason compared to VCH's.

Coverage is easy if you design for 50% with mobiles. Go Public Safety at 95 or 97% and you buy lots of overlap cause of a couple valleys. Throw a VHF hip portable and rubber ducky into the works, along with in-building coverage ... it gets exponentially expensive! And WAY too much coverage on the streets for mobiles. Suddenly SmartZone isn't so smart anymore, cause mobiles don't move to the closest server.

It's all in a days work for ENGINEERING. Nothing is easy! Everything is a compromise.