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#189406 - 11/29/09 04:58 AM Good 4+ minute signal mirror tutorial video on Web
rafowell Offline
Enthusiast

Registered: 11/29/09
Posts: 252
Loc: Southern California
Air Force Academy retired survival training director
Peter Kummerfeldt lectures/demonstrates signal mirrors
for 4:34 of this 5:28 long video clip online:

Raw video: Signaling : News : KXRM FOX 21
http://www.coloradoconnection.com/news/video.aspx?id=374547

The video is one of three survival videos included in
this article by KXRM FOX 21 of Colorado Springs, one each on:
- Fire Building
- Shelter
- Signaling

Matt vs. Wild: Fires, shelter, and signaling
By Matthew Kruger, Sunday, November 08, 2009 at 9:04 p.m
http://www.coloradoconnection.com/news/story.aspx?id=374089

- R. Fowell

_________________________
A signal mirror should backup a radio distress signal, like a 406 MHz PLB (ACR PLB) (Ocean Signal PLB)

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#189408 - 11/29/09 06:18 AM Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: rafowell]
rafowell Offline
Enthusiast

Registered: 11/29/09
Posts: 252
Loc: Southern California
In the video above, Peter mentions seeing a 2"x3" glass mirror flash at 26 mile range, which I can believe - the 1800's surveyor rule of thumb for a naked eye visible mirror flash was 10 miles per inch of side length for a square mirror, which would be roughly 24 miles for a 2"x3" mirror.

Similar results were reported by the U.S. Navy in 1951 signaling from the ground with a 3"x5" glass mirror in "good visibility" to a plane at 5,000 feet altitude reported ranges of:

45 miles with "the plane between the sun and the mirror"
30 miles with the sun at right angles
21 miles "down sun"

You can read about the 1951 Navy experiment in the article: "Mirror Flash Seen 45 Miles", Naval Aviation News, August 1951 page 28 {which is page 30 of the .pdf file), available here:
http://www.history.navy.mil/nan/backissues/1950s/1951/aug51.pdf

Here are videos I made of the mirror flashes from my 3"x5" glass mirror at ranges of 0.7, 11.1 and 43 miles: http://www.youtube.com/watch?v=GwCbgQGmID4

Please note such ranges generally require the air to be quite clear and/or thin - 43 miles is pushing it for a 3"x5" mirror in city atmosphere. I've run tests in more typical "light smog" weather when, despite moving one end to 5,689 ft altitude, and using a 12"x12" mirror, the flash was barely visible with binoculars at 48 mile range, and a 12"x12" glass mirror isn't the most practical piece of survival kit.

In my 43 mile test, both ends were at about 500' elevation, the air was very clear, and the sun to signal line range was 90 degrees. We could see each other's 3"x5" mirror flashes with the naked eye.







Edited by rafowell (11/29/09 06:25 AM)
_________________________
A signal mirror should backup a radio distress signal, like a 406 MHz PLB (ACR PLB) (Ocean Signal PLB)

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#189409 - 11/29/09 06:39 AM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: rafowell]
dweste Offline
Pooh-Bah

Registered: 02/16/08
Posts: 2463
Loc: Central California
Nice. Thanks.

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#189411 - 11/29/09 06:51 AM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: rafowell]
rafowell Offline
Enthusiast

Registered: 11/29/09
Posts: 252
Loc: Southern California
A bit about me, since I just joined the forum:

I'm more into mirror signaling than survival per se.

The white spot in my avatar is not the sun (which was off to the right) but rather a view of the "virtual sun" ("fireball" / "bright light spot") created by the retroreflective bead aiming mesh of a glass signal mirror.

The U.S. military switched to retroreflective aimers on their signal mirrors from their (already deployed) system of "rearsight" mirrors after finding that even the primitive first generation of retroreflective aimers was 2.5 times as effective as the rearsight method for the (admittedly difficult) task of signaling from a bobbing liferaft to a moving plane.

These results and this decision was announced in: "Signaling with Mirrors: Reflex-Button Type of Mirror Adopted for Navy Survival", Naval Aviation News, 15 Sept 1944, pp. 32-33, which can be downloaded from the official government site here: http://www.history.navy.mil/nan/backissues/1940s/1944/15sep44.pdf

I have a site with some photos of old military signal mirrors and links to various pieces of signal mirror history here:
http://www.richard-fowell.fotopic.net/c1663439.html

-R. Fowell
_________________________
A signal mirror should backup a radio distress signal, like a 406 MHz PLB (ACR PLB) (Ocean Signal PLB)

Top
#189412 - 11/29/09 06:59 AM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: rafowell]
yelp Offline
Member

Registered: 06/04/08
Posts: 172
Loc: Colorado
Mr. Fowell,

Thank you for the citation and your observations. We need these much more than the typical "+1" comment left on other forums (which I'm guilty of - so shoot me). Also commendable is the lack of emoticons and LOLs...but that's just my opinion.

Really though, you've provided credible data. That's invaluable, especially considering it might involve one's life.

Cheers!
_________________________
(posting this as someone that has unintentionally done a bunch of stupid stuff in the past and will again...)

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#189519 - 11/30/09 06:08 PM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: yelp]
Glock-A-Roo Offline
Old Hand

Registered: 04/16/03
Posts: 1076
Great stuff Richard, thank you very much.

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#189766 - 12/02/09 10:33 PM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: rafowell]
raptor Offline
Enthusiast

Registered: 04/05/08
Posts: 288
Loc: Europe
Originally Posted By: rafowell
Here are videos I made of the mirror flashes from my 3"x5" glass mirror at ranges of 0.7, 11.1 and 43 miles: http://www.youtube.com/watch?v=GwCbgQGmID4


That is great video you shot. Thanks for it. I am also interested in signaling technology and want to do some tests in the near future.
One thing with these tests that concerns me a little bit is how not to attract unwanted attention and start search and rescue operation smile. I guess one ought not to flash 3x etc.

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#191414 - 12/21/09 04:36 AM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: raptor]
rafowell Offline
Enthusiast

Registered: 11/29/09
Posts: 252
Loc: Southern California
We tested signal mirrors today at 22 mile range, under favorable conditions, using:

(1) 3"x5" glass mirror ( GI issue MIL-M-18371E)
(2) 2"x3" plastic mirror ( American Medical Kits "Rescue Flash" model)
(3) 2"x3" stainless steel with aiming hole

I recorded each on video and put the first two on YouTube.

The 3"x5" (~15 sq. in) mirror was clearly visible at 22 miles with my naked eye - I called out dozens of flashes.

The 2"x3" (~6 sq. in) plastic mirror I saw about four times in 2 minutes with my naked eye. It wasn't because there weren't many times that many flashes heading my direction - you can see the flashes clearly in the video when I'm saying I can't see it on the sound track. I think it is just that with this smaller, less reflective mirror, only the strongest flashes were visible to me.

The 2"x3" (~6 sq. in) stainless mirror I didn't see at all with my naked eye - presumably because the metal was even less reflective than the plastic. it wasn't because it wasn't flashing in my direction - the flashes are clearly visible in the video when I'm saying I can't see it on the sound track. I also could see them when I used my 7x50 binoculars. I'm sure I'd have seen it easily at, say, ten mile range.

The air was quite clear - I could see mountains 94 miles away. The background was good and dark - you can see that in the video. He also had the advantage to signaling almost directly into the sun. Both ends were at about 1000 ft elevation.

I'd expect a bit more range if we were at higher altitude, or with stronger sun, but on the other hand I'd expect to lose range if we were at an angle to the sun.


The 3"x5" glass mirror video is here:
http://www.youtube.com/watch?v=nWG6nRvdFiU
Background and consumer advice on this type of mirror is here:
http://www.equipped.org/phony_signal_mirrors.htm

The 2"x3" plastic Rescue Flash mirror video is here: http://www.youtube.com/watch?v=4JtfpaMiUqQ
This is widely available, e.g. at REI or REI.com.
A good discussion of the development of this mirror is about 40% down this page:
http://www.dougritter.com/amk_psp_faq.htm





_________________________
A signal mirror should backup a radio distress signal, like a 406 MHz PLB (ACR PLB) (Ocean Signal PLB)

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#191422 - 12/21/09 01:13 PM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: rafowell]
KenK Offline
"Be Prepared"
Pooh-Bah

Registered: 06/26/04
Posts: 2179
Loc: NE Wisconsin
I REALLY wish you'd have tested a 2"x3" glass signal mirror too.

That would resolve the question of whether the 2"x3" Rescue Flash's performance was a matter of size or material.

Thanks for the work you did though ... excellent!

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#193211 - 01/11/10 02:14 AM Re: Mirror ranges: 2"x3": 26 miles, 3"x5": 45 miles [Re: KenK]
rafowell Offline
Enthusiast

Registered: 11/29/09
Posts: 252
Loc: Southern California
Originally Posted By: KenK
I REALLY wish you'd have tested a 2"x3" glass signal mirror too.

That would resolve the question of whether the 2"x3" Rescue Flash's performance was a matter of size or material.


Understood. I've shipped my friend a 2"x3" glass mirror (and a 4"x5" stainless steel mirror, as well), and I'm trying to get more volunteers so we can do some side by side simultaneous comparison rather than sequential.
_________________________
A signal mirror should backup a radio distress signal, like a 406 MHz PLB (ACR PLB) (Ocean Signal PLB)

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