Originally Posted By: hikermor
Why on earth do you need a radio to supplement a heliograph network?

  • Most participants don't know Morse
  • Most participants have signal mirrors, a few have heliotropes, but I'm the only one I've known to bring a full heliograph.
  • Often one end of the link is "receive only"(under clouds)
  • Its a lot easier to spot a flash if you know roughly where to look.

A true heliograph, such as a Commonwealth Mance Mark V or a US Marine Corps Field Heliiograph, has three components:
  • 1: Means for aiming the beam to substantially better than the 0.25º beam radius. (See Mance Mark V Demo Video)
  • 2: means for holding that beam steady (tripod, post, etc.), and adjusting the beam to hold it on target as the sun moves.
  • 3: means for modulating the beam for Morse code without compromising (1) & (2) (Shutter, or 4-bar mirror tilt mechanism)

In progression: A true signal mirror usually approximates #1, though seldom to the accuracy of a bespoke heliograph. A heliotrope (which preceded and outlived the heliograph) has both #1 and #2. Lots of Morse has been sent with a heliotrope and a hat for a shutter, but a heliograph makes Morse a lot easier.

Having said all that, I've thought that we should encourage folks to actually build, learn to use, and field heliographs. There are quite a few sets of "make your own" heliograph plans around.

Originally Posted By: hikermor
After all, the US Army operated with mirrors successfully and effectively around the 1890s, well before radio.


Yes - see A short history of the American Heliograph. One year at Operation On-Target, all three of our team's successful links were achieved without any radio frequency benefit, since we had radio issues, and were in a cell phone dead spot. However, ham radio is a huge facilitator.

Originally Posted By: hikermor
There is no better way to give your location to a pilot than a signal mirror - I have done so many times. Ounce for ounce and dollar for dollar, nothing beats a signal mirror and/or a whistle.

Amen, brother ... but in me, you are preaching to the choir.

Speaking of dollars and signal mirrors, the 2"x3" glass Coghlan's "Survival Signal Mirror 9902", which Peter Kummerfeldt seems to think is the best 2"x3" signal mirror currently on the market in the US (and I agree), is less than $8.00 if you shop around, and I've seen the excellent 2"x3" polycarbonate Rescue Flash signal mirror designed by Doug Ritter (and worn under my shirt) on sale for under $7. For those wanting a bright, accurate signal mirror for less than that (or in a larger size), you can put an accurate inexpensive retroreflective aimer on pretty much any plain glass mirror using a square inch of red truck "conspicuity tape", as shown in this video:



If you are stuck with one of the made-in-Taiwan "Phony Glass Signal Mirrors", you can vastly improve it by putting the aimer above on it.
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A signal mirror should backup a radio distress signal, like a 406 MHz PLB (ACR PLB) (Ocean Signal PLB)