Thinking of GMRS in absence of cell service

[Guest Mark]

Our area of mountainous terrain has numerous cell dead zones and am concerned for the wife's travels. Would like an alternative to help fill the gaps in communications if something were to happen on the hour drive from our property to the adjacent interstate. In doing my research, I am aware of the limitations of GMRS and the terrain we have here. 

I am looking for some opinions before I take a financial dive into this. Between the gmrs license, 50w radio with upgraded 6dbi antenna put in our SUV, a repeater placed on our highest part of the property (8535ft) and a handheld close by within 1000ft used as a base. 

I know line of sight is king in good signal, but am unsure what to expect with numerous valleys and hills between the repeater and the SUV's path towards the interstate. There is no hill taller than ours in this direction. The hills that are in-between we have beat by 100ft or so. The terrain actually begins to descend slowly between each hill and valley (canyon) as you progress to the plains.  Although, we are unable to visually see the plains from the highest point of the property.

I know you cannot communicate with a hill or mountain between two radios.

With that said, I'm seeing this situation as the repeater being able to skim the tops of the other hills in that direction as far as it can go. Unfortunately, the roads traveled are in the valleys below those hills all the way to the plains.

What should I expect for transmitting and receiving in those valleys that are usually a couple of hundred feet below the tops of these hills? Would it be worth my time and money to invest in a gmrs in this situation?

I spent a little time on Google Earth to replicate the scenario visually from the top of the property's perspective and took a screenshot to show you folks. Hopefully this shows.

Screenshot

 

Input and suggestions most welcome.

 

[BoxCar]

There is software available that will model the coverage you would get from your repeater installation. The software can show areas with no reception and those with, depending on the repeater's antenna type and height above ground level (AGL). The software I used for coordinating Part 90 frequencies was rented for over $100 per month but was considered one of the most accurate. I suggest you contact a local ham club to see if they have access to a package that can model your proposed installation.

[GreggInFL]

Not a modeler, but I've found this useful: https://www.scadacore.com/tools/rf-path/rf-line-of-sight/

[WRUE951]

check out WIN and/or PAPPA Ham web sites for their UHF repeaters..  If they are operating any UHF repeaters within your area, they should have maps that reflect coverage areas which should give you a good bearing on what to expect with GMRS service...  Also, i understand there are some good open source radio frequency mapping tools if your are a Linux fan..... I've never used them, but i hear the HAMS talk about them

[WRUE951]

2 hours ago, GreggInFL said:

Not a modeler, but I've found this useful: https://www.scadacore.com/tools/rf-path/rf-line-of-sight/

google earth has the same too with a little more added info.   right click on a line between two points and choose 'elevation profile'   

[WRYS709]

16 minutes ago, WRUE951 said:

check out WIN and/or PAPPA Ham web sites for their UHF repeaters..  

WIN maybe, not PAPA as his screenshot seems to be next to Interstate-25 in the Rockies.

[GreggInFL]

6 minutes ago, WRUE951 said:

google earth has the same too with a little more added info.   right click on a line between two points and choose 'elevation profile'   

Good to know.  Thanks!

[Guest]

9 hours ago, Guest Mark said:

[...] if something were to happen on the hour drive from our property to the adjacent interstate.[...]

 

My first question is always: What is that "something" you are afraid off ?!?

... and I am not trying to be funny or mean or make things more complicated!

 

If your goal is to check in with your wife so that you can start the pot-roast on time, any radio solution with spotty coverage will do -> you both will learn at what spot during the drive the communication is clear and you will work around the 'blind spots'.

If increasing reports of "axe-murderers" on mountain roads are concerning you ... you get the point!

 

In "tricky terrain", you often find yourself in need of multiple option hoping that one is getting through in that specific situation. A ham with privileges and radios on multiple bands and with training on all those will find a solution in most scenarios Mainly, as that ham knows where to look (what band at what location at what time in what weather...)

 

Our "not really that interested in radios" better halfs are often willing to invest a minimum of listening time to our "cool" solutions but at the end of the day, they might find themselves with a flat, a jack, and a radio without remembering how to use either.

 

I know that this is not the shiny tech answer you hoped for, but it might give you an idea about some other aspects of "preparedness" ...

[Guest Mark]

2 hours ago, GreggInFL said:

Not a modeler, but I've found this useful: https://www.scadacore.com/tools/rf-path/rf-line-of-sight/

Wow. That's useful. Definitely a better perspective. Unfortunately the graphing is turning the feasibility of this working away in my thought process. This is the pdf showing 18m above ground at the hill top a 3m at the vehicle at the interstate. Distance as the bird flies is 22 miles I believe.

Pdf- line of sight

Not looking for guarantees here, but what are the odds of this signal bouncing around in the canyons or neighboring hills. Not for a clear broadcast, but some readable transmissions?

[WRQC527]

56 minutes ago, Guest Mark said:

what are the odds

I'm no Jimmy The Greek, but the odds are definitely not in your favor.

[Guest Mark]

6 minutes ago, WRQC527 said:

I'm no Jimmy The Greek, but the odds are definitely not in your favor.

I appreciate that. That's what I'm looking for.

[GreggInFL]

6 hours ago, BoxCar said:

I suggest you contact a local ham club to see if they have access to a package that can model your proposed installation.

This sounds like the best approach.

A Mickey-Mouse test might be to grab a couple of HTs and try to get over that first hill.  No guarantee that you could somehow extrapolate the results, but it scales to only ~2.5 miles and might tell you something. 

[Guest Mark]

10 hours ago, WRXD372 said:

 

My first question is always: What is that "something" you are afraid off ?!?

... and I am not trying to be funny or mean or make things more complicated!

I believe moderation protected the community earlier in my long drawn out reasons why BFE in the west is really BFE. Especially with no phone service and sparse population along her hour long route. Also the fact that the wife does not operate as a mobile mechanic, mobile body shop (in case of collisions with numerous suicidal deer and elk), nor have a tow service following her up and down the mountain.  With those few reasons, I will stop there.

I appreciate all the suggestions everyone gave. Just wanted to make sure I'm not missing any new science that could benefit my placement and situation.

I believe I'll have to come to terms with the not surprising conclusion that GMRS is a pipe dream for this purpose. Of course I've still ordered a few radios for the property in a SHTF moment and long distance shout outs to far away operators. But did not invest in a repeater or 50w radio for the SUV.

I think I'm going to look more into a sat text capable communication device that has a low cost monthly plan. Talking $11 a month.  Don't like monthly bills eating into my account, but I believe this will fill the communication void that I feel needs to be met.

 

 

[SteveShannon]

I would try 40 meter mobile ham radios. You might have to try NVIS.

 

[Guest Mark]

13 hours ago, Sshannon said:

I would try 40 meter mobile ham radios. You might have to try NVIS.

 

Interesting. Honestly was trying to stay away from complication. Lol.  That is opening a fresh can of ham radio operation. But this NVIS antenna is interesting and would seem to suit our placement and situation.

I'm assuming based on the low frequency operation, this antenna is only for ham radio operation? I'm thinking this would also reduce the need for a repeater setup on the highest point of the property?  Side question to that! Is a repeater in this two way communication even mandatory? Can the NVIS connection be made straight to the base radio on the property side? 

After a crash wiki into the 40m radios understanding these low frequencies operate best under minimum to no solar (sunset to sunrise) for far out distances, would it be out of the realm that this could operate during mid day for the much smaller distances (within 20 miles) I'm looking at?

[SteveShannon]

24 minutes ago, Guest Mark said:

Interesting. Honestly was trying to stay away from complication. Lol.  That is opening a fresh can of ham radio operation. But this NVIS antenna is interesting and would seem to suit our placement and situation.

I'm assuming based on the low frequency operation, this antenna is only for ham radio operation? I'm thinking this would also reduce the need for a repeater setup on the highest point of the property?  Side question to that! Is a repeater in this two way communication even mandatory? Can the NVIS connection be made straight to the base radio on the property side? 

After a crash wiki into the 40m radios understanding these low frequencies operate best under minimum to no solar (sunset to sunrise) for far out distances, would it be out of the realm that this could operate during mid day for the much smaller distances (within 20 miles) I'm looking at?

This can work during daylight hours. It does require lower frequencies. It’s what the military uses for nearby communications. No repeater necessary and a dipole at 1/10 wavelength above the ground is all that’s needed for an antenna, but a horizontal loop on top of a vehicle works okay also (Caution: I have read!!  I am just starting to try this myself.)

[AdmiralCochrane]

I am interested in trying NVIS, but much of what I read about it says it is DIFFICULT.  That won't stop me from trying 

[WRZY946]

NVIS looks fascinating but I'm unsure if I'll ever go that deep into ham radio. At this juncture I'm just barely getting started with GMRS. Though I do appreciate this thread! It's an example of how important it is to figure out your use cases and learn how to mitigate shortfalls with the service, and/or issues with your terrain.

[SteveShannon]

7 hours ago, AdmiralCochrane said:

I am interested in trying NVIS, but much of what I read about it says it is DIFFICULT.  That won't stop me from trying 

I’m interested too. The military 2259 antenna is a great model to follow. That’s a crossed dipole with a 15 foot central pole  

At its simplest a NVIS antenna is a dipole that’s placed low rather than high so propagation goes nearly vertically. 
 

Heres a good summary with interesting links: https://practicalantennas.com/applications/nvis/as2259/

[DONE]

Going back to the idea of GMRS for communications.  If you are looking to map coverage of a repeater in the area, try RadioMobile.  Just google it.  That will generate coverage maps.  Be sure to use LOW GAIN repeater antenna's if there is a lot of up and down or you are placing the antenna significantly higher than any part of your expected coverage area.  High gain antenna's will cause issues when close into the repeater if it's a lot higher in elevation.

If you are looking for this to be a solution when cell is down, you need to consider why cell service would be down.  Cell towers require a couple things to operate.  First is power.  If the cell sites have no power, will your repeater.  If not, it's is not going to work unless you power it off some other source, or have a backup source when the power is out. 

Second is connectivity to the outside world.  Cell sites can't communicate with the phones if they have no connectivity to the outside world.  Think of it like an Internet outage.  A repeater in local service would NOT be effected by an Internet outage, but a linked repeater or repeaters will have issue if they are reliant on Internet connectivity to link between the different sites. 

Now the HAM and NVIS stuff is all great for base to base communications.  But that is HF frequencies.  You are NOT going to build an NVIS antenna for GMRS and have it work.  The problem is that the UHF frequencies will NOT bounce off the Ionosphere.  They will just go right past it and out into space.  So NVIS doesn't work for GMRS. 

 

[SteveShannon]

1 hour ago, WRKC935 said:

Now the HAM and NVIS stuff is all great for base to base communications.  But that is HF frequencies.  You are NOT going to build an NVIS antenna for GMRS and have it work.  The problem is that the UHF frequencies will NOT bounce off the Ionosphere.  They will just go right past it and out into space.  So NVIS doesn't work for GMRS. 

That’s true, but really, nobody was talking about doing NVIS on GMRS frequencies. 

[Lscott]

1 hour ago, WRKC935 said:

High gain antenna's will cause issues when close into the repeater if it's a lot higher in elevation.

That’s why some expensive high gain repeater antennas have a “down tilt” specification. These antennas are specially designed to direct a bit more of the power downward closer to the antenna site. That improves close in repeater coverage. 

https://www.repeater-builder.com/antenna/downtilt.html

https://www.kpperformance.com/Antenna-Downtilt-A-Practical-Overview.html