Coverage Prediction

[SteveH]

I am new to GMRS and basically a novice in UHF in general. My ham life has pretty much consisted of using 2 meter repeaters plus (to a much greater extent) HF and 6 meter voice and digital.

 

I am thinking about setting up one or two GMRS repeaters to provide service to some areas along the midcoast of Maine. At least initially I want to avoid the bureaucratic hassle of trying to locate the repeaters on commercial towers. So, our group is looking at who amongst us has houses that are in somewhat favorable (from a coverage perspective) locations. For example, although I am basically at sea level on the coast, it does appear that I can give good coverage to most of the nearby towns as well as possibly to some of the nearby islands.

 

This all brings up the use of coverage prediction software and the proper application of those tools. I am coming up the learning curve with Radio Mobile but it looks like many of the people here use the online calculator that's at http://lrcov.crc.ca/. Compared with Radio Mobile, this one is very easy to use, at least for first order coverage estimates. Radio Mobile allows you to provide a pretty complete profile for all stations in the network as required to complete the full two-way picture whereas the online tool only gives estimates of field strength around the transmitter.

 

That said, I'm curious as to what tools the people here are using and, especially for the online tool, how you evaluate the

3 default field strength ranges (45-60, 60-75, 75-100 dBuV/m) to actual useful coverage for mobile and fixed users. Also, anything else in your experience that relates these tools to real life.

 

Below is a sample plot using the online tool.

http://belljar.net/OH_Coverage.jpg

 

Thanks,

Steve

 

 

 

 

[Shriekmau]

JohnE is definitely one of the more experienced members with these types of software. I will message him and see if he can provide some insight.

[SteveH]

Thanks Jeremy.

[JohnE]

I find it close enough for what I use it for.

RED is for portable

BLUE is mobile - 25W w/unity antenna

GREY is where it can be heard in a mobile but not nessicerily able to talk back. I can hit it w/my high power mobile(45W) and 5dB antenna I places though.

as for settings

I use known power at the antenna and add 2dB for the antenna gain since all the antennas I use are rated in dBd not dBi.

I do not reset the RX setting at all they stay as is.

I have wanted to do futher field testing to get a more accurate set of numbers to put  in that program but just haven't had the time.

I forgot to tell you to set the dBuV/m settings as I have them the default settings I believe are for broadcast.

look at my thread here this will better explain how I set it up. this will give you a general idea of how far the your machine can transmit . the receive side is a little different.

http://forums.mygmrs.com/topic/8-ers-ny-650/?do=findComment&comment=437

 

[SteveH]

Thanks John. I had looked at both the ERS 650 and 575 threads but 1) I missed the changes you made to the default field strength settings and 2) I didn't read far enough to see your explanation. Duh. Thanks for repeating it here.

 

Below is the plot I showed above but with the adjusted field strength ranges. Antenna is a 9 dB Comet, knocked down a couple for losses.

 

Steve

 

http://belljar.net/OH_Coverage_2.jpg

[JohnE]

9dBd or dbi

[SteveH]

Antenna's a Comet CA-712EFC, 9 dBi.

 

Steve

[JohnE]

I was unaware that radio mobile was now more user friendly. last time I played w/it you had to download a bunch of files.

going to fart around w/it tonight.

[SteveH]

I presume you are referring to the installer that gives you everything. It does make it a lot easier to work with.

 

Steve

[Guest spd641]

look at my thread here this will better explain how I set it up. this will give you a general idea of how far the your machine can transmit . the receive side is a little different.

http://forums.mygmrs.com/topic/8-ers-ny-650/?do=findComment&comment=437

 

look at my thread here this will better explain how I set it up. this will give you a general idea of how far the your machine can transmit . the receive side is a little different.

http://forums.mygmrs.com/topic/8-ers-ny-650/?do=findComment&comment=437

I have tried but this software it is driving me nuts.I keep getting so many errors...William

[SteveH]

I'm using Firefox on two computers, one is a WinXP the other is running Linux Ubuntu. No issues with the tool.

 

Steve