Guest Kirk Posted January 13, 2021 Report Share Posted January 13, 2021 Hello everyone, I am glad I have found this site. Newish to radios and have been doing a ton of research the past few days. We are looking to set up emergency communications between 5 properties in a roughly 10 mile radius. I have been looking at the GMRS radios and am trying to decide what the best equipment set up would be to accomplish this. We are located in Maine where there are hills, mountains, and trees. I have not been able to find any repeaters in the UHF band in our area. Everything seems to be just the VHF for police, fire, etc. Our property is centrally located to the other properties so initially my thought was, like many newbies apparently, set up a repeater at our home for the other 4 properties to connect to. However I came across Corey's post on building a repeater system and am now reconsidering everything. I am looking at the Midland MXT-400 mobile radios as well some used UHF Kenwood TK-8102 off ebay. Both these are around 40watts I believe. My question is, and I know with GMRS its all about line of sight, If we all had powerful mobile radios with good antennas set up pretty high on our properties, would 10-12 miles be doable? Most of us are located on the sides of mountains but we have hills/mountains in between us about 250-300' higher than our properties. I know that without know the precise specifics of the terrain it will be hard for anyone to give a direct answer but any insight would be greatly appreciated. Thanks! Quote Link to comment Share on other sites More sharing options...
Guest mike Posted February 12, 2021 Report Share Posted February 12, 2021 This is a really cool tool that may be helpful in helping you . https://www.scadacore.com/tools/rf-path/rf-line-of-sight/ Quote Link to comment Share on other sites More sharing options...
axorlov Posted February 12, 2021 Report Share Posted February 12, 2021 300' high hills could be a problem. However, with the help of diffraction and reflection of radiowaves might be doable. And if you can put 50' mast, that would be better. Only practical experiment will tell for sure.The TK-8102 with it's wide-band capability is much better than anything from Midland. In a situation like yours every tiny bit helps, like better receiver on Kenwood and wide-band. It is also much cheaper to experiment with: below $100 vs $250 Quote Link to comment Share on other sites More sharing options...
axorlov Posted February 12, 2021 Report Share Posted February 12, 2021 Another thought: if your property is centrally located, that is necessarily a best spot for a repeater (or even simplex). Other locations might provide better path to other sites. Quote Link to comment Share on other sites More sharing options...
mbrun Posted February 13, 2021 Report Share Posted February 13, 2021 I second the use of the scadacore tool to determine whether you can achieve line of sight. Round up the exact geo coordinates of your 5 proposed sites, and then two at a time plug them into their tool. Then enter the proposed elevation of antennas at each site and see what you get. If the graph that results shows an uninterrupted line then there is reasonable chance of success. You will need to try all combinations to see who will have trouble reaching who. Take a screen capture of each combination you try for further reference. https://www.scadacore.com/tools/rf-path/rf-line-of-sight/ It is funny reading your post about a 5 site project. I have a neighbor actively working on doing exactly that. Since they live next door, I was recently able to facilitate some tests for their family network since I have the tools and equipment available. We started with scadacore to initially confirm it was probable, then we mocked it all up and demonstrated it viable. Hello everyone, I am glad I have found this site. Newish to radios and have been doing a ton of research the past few days. We are looking to set up emergency communications between 5 properties in a roughly 10 mile radius. I have been looking at the GMRS radios and am trying to decide what the best equipment set up would be to accomplish this. We are located in Maine where there are hills, mountains, and trees. I have not been able to find any repeaters in the UHF band in our area. Everything seems to be just the VHF for police, fire, etc. Our property is centrally located to the other properties so initially my thought was, like many newbies apparently, set up a repeater at our home for the other 4 properties to connect to. However I came across Corey's post on building a repeater system and am now reconsidering everything. I am looking at the Midland MXT-400 mobile radios as well some used UHF Kenwood TK-8102 off ebay. Both these are around 40watts I believe. My question is, and I know with GMRS its all about line of sight, If we all had powerful mobile radios with good antennas set up pretty high on our properties, would 10-12 miles be doable? Most of us are located on the sides of mountains but we have hills/mountains in between us about 250-300' higher than our properties. I know that without know the precise specifics of the terrain it will be hard for anyone to give a direct answer but any insight would be greatly appreciated. Thanks! MichaelWRHS965KE8PLM Quote Link to comment Share on other sites More sharing options...
MacJack Posted February 13, 2021 Report Share Posted February 13, 2021 Kirk, you are forward thinking... I like all the replies to use scadacore which I will check it out. I have been using https://www.ve2dbe.com/rmonline_s.asp which gives me a great view for placing a repeater based on elevation off of US TOPO maps... Going to play with scadacore to see what is up... I have wanted to attached some screen shots of what my repeater footprint would look like... but file to big per this forum limits. Sorry, send me a pm with your email address and will send you images... Jack EDIT: Just played with scadacore https://www.scadacore.com/tools/rf-path/rf-line-of-sight/ it nice for line of sight... You need to know your GPS coordinates before you start... Just fill in and click plot... Now I'm going to try it with my 5 watt handheld. Quote Link to comment Share on other sites More sharing options...
Guest mike Posted February 13, 2021 Report Share Posted February 13, 2021 On the SCADACORE tool GPS coordinates are not required, you can just go to blue & green dots on the map & drag them to your locations and progressively zoom in on the map to get the adzact location. The tool does have a few quirks, like sometimes if you change antenna height value to were it is line of site the line stays red instead of going green as it should. You have to redo it with new value from the start & it will work. I have played around with it a lot as I live in a valley with mountains all around & ridges in the valley. It really helps to get some idea of what is possible, but if its not line of site (sounds like not for you) Field testing may be best. I have Did Scadacore for several locations & thought it probably wouldn't work, then field tested & made contact between the locations I had mapped on SCADACORE & had good communications. This was on 5 watt HTs with upgraded HT antennas talking simplex. For me the obstacles breaking the "line of sight" line were mountains (edges of , not like the mountain was right in between the 2 radios. But the edge of the mountain was blocking the straight line. So, in my limited experience, it didn't have to be a literal line of sight. The signal was able to work around the edges of the mountains some. This was at a range of 15+ miles , though both radios were at a much higher elevation than the general terrain (we were on the sides of mountains above the same valley). I have had less success (but some) in the valleys working around similarly per-portioned obstacles. One time we were 1.5 miles apart & I hiked under "the shadow" of the mountain from the other radio location & lost signal very quickly. If you dont have luck with HT or mobile testing , mabe try rigging up a temporary antenna. I have heard of people pulling over a high tree limb. May have to use a bow & arrow with fishing line to start the cord to pull up antenna. I have heard of people do this with an inexpensive Ed Fong commercial J pole antenna (it is just a 5 foot piece of PVC pipe (as far as pulling up a tree goes)good luck, should be fun trying all this kind of stuff ! Quote Link to comment Share on other sites More sharing options...
mbrun Posted February 14, 2021 Report Share Posted February 14, 2021 On the SCADACORE tool GPS coordinates are not required, you can just go to blue & green dots on the map & drag them to your locations and progressively zoom in on the map to get the adzact location....Hello Mike. Having used scadacore quite a bit now, I personally have landed on just moving the colored dots when I need a quick ball park check. However, when comparing doing multiple sites I find it easier to use google earth or google maps to get exact coordinates of where the antennas are probable to go, same them out to a document for later reuse. Then I can just copy and paste them as needed to run the different scenarios. One of my biggest pet peeves with this tool is that even the slightest change in position of a dot causes the antenna height to be reset to the default. I wish it would retain it. You are correct that there is no guarantee that you will or will not have coverage. But the probability of one or the other increases. Onsite testing is the one sure-fire way to know for certain, no doubt about that. MichaelWRHS965KE8PLM Quote Link to comment Share on other sites More sharing options...
AdmiralCochrane Posted February 15, 2021 Report Share Posted February 15, 2021 Cool tool. I just mapped my favorite locations and the repeaters I use and a potential repeater that sits between me and my brother. Quote Link to comment Share on other sites More sharing options...
mbrun Posted February 15, 2021 Report Share Posted February 15, 2021 Cool tool. I just mapped my favorite locations and the repeaters I use and a potential repeater that sits between me and my brother.Agreed. Do also consider that the tool does not take into account vegetation or man-made obstacles, all of which decrease range dramatically so you will need to factor that into your planning. There is another site up in Canada that features pretty advanced calculator that can aid you in estimating repeater coverage. It is run by a professional RF Engineer that is also an amateur radio operator. It is on his personal amateur radio site. I have used it as have others on this site. I am drawing a blank on the address at the moment, but I believe I saw MacJack reference it last. MichaelWRHS965KE8PLM Quote Link to comment Share on other sites More sharing options...
n4gix Posted February 15, 2021 Report Share Posted February 15, 2021 Radio Mobile Online https://www.ve2dbe.com/rmonline_s.asp Quote Link to comment Share on other sites More sharing options...
mbrun Posted February 16, 2021 Report Share Posted February 16, 2021 Radio Mobile Online https://www.ve2dbe.com/rmonline_s.aspThanks for posting the link. MichaelWRHS965KE8PLM n4gix 1 Quote Link to comment Share on other sites More sharing options...
Extreme Posted February 24, 2021 Report Share Posted February 24, 2021 Kirk, you are forward thinking... I like all the replies to use scadacore which I will check it out. I have been using https://www.ve2dbe.com/rmonline_s.asp which gives me a great view for placing a repeater based on elevation off of US TOPO maps... Going to play with scadacore to see what is up... I have wanted to attached some screen shots of what my repeater footprint would look like... but file to big per this forum limits. Sorry, send me a pm with your email address and will send you images... Jack EDIT: Just played with scadacore https://www.scadacore.com/tools/rf-path/rf-line-of-sight/ it nice for line of sight... You need to know your GPS coordinates before you start... Just fill in and click plot... Now I'm going to try it with my 5 watt handheld. Save as: .jpg works. Quote Link to comment Share on other sites More sharing options...
MacJack Posted February 25, 2021 Report Share Posted February 25, 2021 Nice... Looks like Nevada. I would upload my jpg but having issues on how on this site. I can get the file down so small I hope you can see it. I do like this tool as well https://www.ve2dbe.com/rmonline_s.asp as they both have a place...JackSave as: .jpg works. Quote Link to comment Share on other sites More sharing options...
OldRadioGuy Posted February 28, 2021 Report Share Posted February 28, 2021 That scadacore is a really cool and useful tool.Thanks to the guy who posted it.It seems to perfectly validate what I find with my radios.You can get away with "grazing" terrain interference but not much more. If you have terrain that is simply not conquerable with towers you may find that longer wave bands such as Ham 80M would do the trick.Longer waves are much more forgiving of terrain but this is a whole other universe from GMRS.It requires Ham licensing and very expensive radios with large wire antennas so may not be your answer.A repeater probably would be cheaper. A more radical solution is to look for possible reflections like bouncing off hills with a beam antenna.A guy on our 2m repeater last night was talking about having to point his antenna the "opposite" direction to bounce off a hill and talk to a station 50 miles the other way.He was using SSB on 2 Meters and probably 100W of power so he was pushing it.Obviously not an efficient scheme so need plenty of antenna gain (on both ends) and sufficient power. A co-worker years ago who was an antenna designer at Lockheed put a sheet of metal-clad plywood up on the hill behind his house to get Boston TV from Milford, NH.It worked quite well once he got it aimed right (using walkie talkies). Of course he was only 100-200 feet from the plywood sheet so it "looked pretty big" to his antenna. Vince Quote Link to comment Share on other sites More sharing options...
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