Author Topic: 6.5 mile signalling test - success!  (Read 2886 times)

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Offline PetrifiedWood

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6.5 mile signalling test - success!
« on: October 09, 2015, 10:32:08 AM »
Some of you have been following the cheap flashlight thread in the Gear Reviews section here: http://bladesandbushlore.com/index.php?topic=7801.0

Anyhow, I tested this flashlight around dusk yesterday. My wife was a little over 6.5 miles away in the car. I aimed the flashlight at her position and turned it on using the strobe feature. She reported that she could see it.

To take it a step further, I flashed it at her and had her report when she saw it and when she didn't. She was able to see it and correctly tell me when I had it turned on.

She did report that without the strobe feature, it just looked like any of a number of other lights in the distance and could be easily overlooked.

So, to summarize, $4 cheap flashlight as signalling device, not too bad! :D

Online wolfy

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Re: 6.5 mile signalling test - success!
« Reply #1 on: October 09, 2015, 12:45:50 PM »
Here's a somewhat interesting factoid that was brought to mind when I read your post, PW.....

Assuming that you were both at the same elevation and unless one of you was in an elevated position, you were right at the point of the natural curve of the earth interfering and making that signal impossible to see......If I recall correctly, that would be around 6' at a distance of 10 miles.
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Offline PetrifiedWood

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Re: 6.5 mile signalling test - success!
« Reply #2 on: October 09, 2015, 12:58:19 PM »
Here's a somewhat interesting factoid that was brought to mind when I read your post, PW.....

Assuming that you were both at the same elevation and unless one of you was in an elevated position, you were right at the point of the natural curve of the earth interfering and making that signal impossible to see......If I recall correctly, that would be around 6' at a distance of 10 miles.

That is an interesting fact. She was actually lower than if she had been standing, because she was seated in the car. However my location was at least 50 feet higher in elevation (rough guess) due to the topography. I could see her headlights from my location as well.


Scratch that. She was between 5600 and 5800' contour lines on the map, and I am just above a 6400' contour line. so 6400-5700= 700' difference. I didn't realize the highway gained that much elevation in 6 miles but I guess it does.
« Last Edit: October 09, 2015, 01:03:52 PM by PetrifiedWood »

Online wolfy

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Re: 6.5 mile signalling test - success!
« Reply #3 on: October 09, 2015, 01:55:45 PM »
Here's a somewhat interesting factoid that was brought to mind when I read your post, PW.....

Assuming that you were both at the same elevation and unless one of you was in an elevated position, you were right at the point of the natural curve of the earth interfering and making that signal impossible to see......If I recall correctly, that would be around 6' at a distance of 10 miles.

That is an interesting fact. She was actually lower than if she had been standing, because she was seated in the car. However my location was at least 50 feet higher in elevation (rough guess) due to the topography. I could see her headlights from my location as well.


Scratch that. She was between 5600 and 5800' contour lines on the map, and I am just above a 6400' contour line. so 6400-5700= 700' difference. I didn't realize the highway gained that much elevation in 6 miles but I guess it does.

This natural geographical phenomenon becomes most obvious on a large body of water.
The only chance you got at a education is listenin' to me talk!
Augustus McCrae.....Texas Ranger      Lonesome Dove, TX

Offline PetrifiedWood

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Re: 6.5 mile signalling test - success!
« Reply #4 on: October 10, 2015, 08:33:16 AM »
Here's a somewhat interesting factoid that was brought to mind when I read your post, PW.....

Assuming that you were both at the same elevation and unless one of you was in an elevated position, you were right at the point of the natural curve of the earth interfering and making that signal impossible to see......If I recall correctly, that would be around 6' at a distance of 10 miles.

That is an interesting fact. She was actually lower than if she had been standing, because she was seated in the car. However my location was at least 50 feet higher in elevation (rough guess) due to the topography. I could see her headlights from my location as well.


Scratch that. She was between 5600 and 5800' contour lines on the map, and I am just above a 6400' contour line. so 6400-5700= 700' difference. I didn't realize the highway gained that much elevation in 6 miles but I guess it does.

This natural geographical phenomenon becomes most obvious on a large body of water.

It's also part of the reason you shouldn't believe the "18 mile range" claims some of the FRS walkie talkies boast about. Unless you are on two mountain tops 18 miles apart, you aren't going to get anywhere near that kind of range, especially with a planet in the way. :D

Offline lgm

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Re: 6.5 mile signalling test - success!
« Reply #5 on: December 07, 2015, 08:16:36 PM »
Well I am impressed by 6+ miles. I have thought about doing some testing but never have.
Thanks .
As for the radios I have never got better then 2 miles under any conditions.
What a great day to be outside.

Offline PetrifiedWood

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Re: 6.5 mile signalling test - success!
« Reply #6 on: December 08, 2015, 10:11:21 AM »
I have gotten really great range with a handheld "walkie talkie" ham radio running 5 watts (to the international space station) but that's with a Yagi antenna and favorable conditions.

FRS radios have 10x less power at 500 milliwatts, and a fixed antenna so you can't use one with more gain.

Still, on two mountain tops or ridges I would expect 10 miles could be possible with FRS. GMRS requires a license but you can use more power.

Still, if you are going to bother to get a license, the ham license is the way to go.

Online wolfy

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Re: 6.5 mile signalling test - success!
« Reply #7 on: December 08, 2015, 10:34:52 AM »
I wonder if anyone that has these FRS/GMRS combo radios actually goes to the trouble of buying the license required for the GMRS side of them?   I wouldn't dream of clandestinely using mine in such a manner, but I'm certain there are those that do.  ;D

We have used them to communicate between the combine, grain cart & truck driver during harvest when cell phones refuse to find a tower.  Line-of-sight range is very good on the little radios, but talking when a hill or two gets in the way is frustrating.  >:(
The only chance you got at a education is listenin' to me talk!
Augustus McCrae.....Texas Ranger      Lonesome Dove, TX

Offline lgm

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Re: 6.5 mile signalling test - success!
« Reply #8 on: December 08, 2015, 04:52:10 PM »
Now the kids are bigger we use ours less. Mostly when camping if we split up we use them. Good on road trips also when you take more then one vehicle.
What a great day to be outside.