MILEAGE RANGE

When any given Department is given a P25 program to use, how do they deter man the mileage distance
coverage for that department ? I notice that many department's have diff mileage coverage.

retiredmich said:

When any given Department is given a P25 program to use, how do they deter man the mileage distance
coverage for that department ? I notice that many department's have diff mileage coverage.

Click to expand...

The radio manufacturer figures it out.
Of course they are different. Seattle, WA terrain is different from Miami, FL isn't it?
How do you know the mileages are different?

If you go in to the " Radio Reference Database " click on ANY state & then on any County, then their community's that are listed, the mileage are diff from each other. Like LV CO KS, each community is diff in mileage coverage, I was just wondering how they deter men the mileage coverage in distance.

Each communications set up is different. If I place a 100 foot tower on top of a mountain at 5000 feet my radio coverage will be much greater than my antenna placed on say a five story building. Then you have reapeters placed throughout the community and this will also give greater coverage than just a 100 foot tower placed in the middle of town. I hope this helps answer your question.

YES it does, Thank you.

There are coverage prediction programs that given the information of the transmitter and receiver locations (along with their technical specifications) can predict the coverage area.
BB

retiredmich said:

If you go in to the " Radio Reference Database " click on ANY state & then on any County, then their community's that are listed, the mileage are diff from each other. Like LV CO KS, each community is diff in mileage coverage, I was just wondering how they deter men the mileage coverage in distance.

Click to expand...

I wouldn't count on any of those predictions. There are too many variables, like foliage or no foliage, receiver height, transmitter height, etc., etc.
Also, especially with portable radios, you can move the antenna just a bit and you will hear it or not. At 800MHz 1/4 wavelength is only 3-1/4 inches. So with a weak signal, moving the antenna 3-1/4 inches will hit a peak or a null.

Unfortunately we HAVE to count on those predictions as those results represent the coverage test we have to meet in order to get system acceptance. And yes all of those variables have to be put into the software. The coverage area is broken up into grid squares (usually less than a mile) and we have to take a measurement in each grid. Depending of the percentage of grid coverage requirements we have to measure a signal equal to or greater than that determined by the prediction software. 95% is the usual requirement of grid squares that must be passed. There may be other caveats such as each grid square measurement must be from an accessible road or not in the middle of lakes. A coverage requirement and coverage test are usually the number 1 and 2 items in a system design and contract.
BB

retiredmich said:

When any given Department is given a P25 program to use, how do they deter man the mileage distance
coverage for that department ? I notice that many department's have diff mileage coverage.

Click to expand...

Unfortunately, I didn't find the correct answer in any of the above replies as it relates to the subject at hand. The radius coverage is simply the radius from the center of the service area to the farthest edge. If a city is 12 miles in diameter, the range would be a 6 miles radius.

The range as it relates to scanners and RR has nothing to do with how far a signal COULD travel.

The reason the radii are different is because each municipality is a different size.

I do be leave I have phrased my question wrong, I should have used the phrase of " radius " in stead of
mileage, MY fault !

retiredmich said:

I do be leave I have phrased my question wrong, I should have used the phrase of " radius " in stead of
mileage, MY fault !

Click to expand...

Still, are you talking about the RANGE figures in the RR database or in scanners such as the BCDx36HP series? If so, my answer is the correct one.

Not talking about scanners. I am asking why do County's have diff mile ranges , why aren't they all the same in distance coverage ?
























































Leavenworth County > Leavenworth County

Unique ID:
14175

Latitude:
N 39.19 (County)

Longitude:
W -95.07 (County)

Range:
17 Miles (County)

I will try to make this as clear as possible. Pertaining to the mileage distance, When you click on the
RRDB & you pick a state & then pick a county in that state & open that county like LV CO in KS, then you go to LV CO in that list & click on the arrow to bring up the radius for LV CO, it shows how many miles it covers with in the radius, IF I click on Buchannan Co Mo & I can see that LV CO KS is in that radius for Buchannan Co MO, SO if LV CO KS is in that radius then why cant I hear them dispatch ?
If any CO is in that radius does that not mean that CO should be able to hear the transmission?

Each of these database items: County, conventional frequency sub-category, trunked radio system and talkgroup group - has a location (Lat/Long) and range associated with it. The database admin handbook instructs the volunteer database admins to assign the most appropriate coverage (to the extent that a perfect circle can) that covers the area of that particular object. So in the case of a county, a point is determined close to the center and a range is specified so that the circle encompasses the county's area with minimum overlap. Same goes for areas covered by conventional sub-categories, trunked radios systems and talkgroup groups. These points and ranges are "best guesses" determined by the admins.

This information is used by scanners and scanner programming applications that support location-based programming. For example, the Uniden HP-1 scanner allows users to specify a zip code (ie point) and range to determine which channels and systems are scanned, based on the database objects that fall within the specified range of the specified zip code. Likewise, the GRE PSR-800 can pre-load scanning objects based on a similar method. Some scanners even support integration with GPS receivers that can activate scan objects as one moves into a particular area, and deactivate objects as one leaves a particular area.

If you find location information on a database object that isn't accurate, please submit a database request to have the location information corrected. We've seen reports of objects from across the country show up in location-based scan lists because of mistakes in the location information.

Thank you very much for that explanation, You have answered my question.

retiredmich said:

Not talking about scanners. I am asking why do County's have diff mile ranges , why aren't they all the same in distance coverage ?

Click to expand...

Simple answer: Because their geopolitical coverage is different.
Not all cities are 8 miles in radius, for example.

New York is much larger than Buffalo.