Heliographs

[foggycoder]

It's not quite right to post this thread in "Vintage Telegraph Apparatus" because:

• heliographs are not necessarily vintage - it's true they came into widespread use for communications in the 19th century but you still find them in modern survival packs (albeit intended for attracting attention rather than for morse communications)
• they're not telegraph apparatus (because they don't use wires). If anything they are very very very high frequency waves (or streams of photons, depending on your views on wave-particle duality). Very definitely "line of sight" though.

but I don't know where else on the forum to post this!

There are two techniques for using them:[list type=decimal]
[*]Single-sided mirror: hold the mirror with one hand, close to your face, so that you can see through the central hole; hold the index finger of your other hand out in front of you, so it covers the target; move the mirror so it shines the reflection of the sun onto your finger; move your finger away so that the reflection of the sun is now shining on the target. A spare Compact Disc or DVD makes an impromptu single-sided heliograph!
[*]Double-sided mirror: difficult to put into words, but this WW2 video https://youtu.be/vmnRrCVBaP0 shows the technique really well.[/i]
[/list]

Some of the more-sophisticated communications heliographs had two mirrors (for when the sun was behind the sender - the second mirror reflected the sun onto the primary mirror).

I'll also post a couple of examples of heliographs.

 

[foggycoder]

Portuguese Type 938C

A relatively modern hand-held communications heliograph with two mirrors and a shutter operated by a key.

 

[foggycoder]

USAF MIL-M-18371E and other retro-reflective heliographs

The current survival and signalling heliograph for the US Air Force. MIL-M-18371E signal mirrors come in two sizes: 2"x3" (Type I) and 3"x5" (Type II), and are sold to civilians by the government contractor, S.I. Howard Glass, directly (wholesale - qty 100) and through distributors. £30 on amazon.co.uk for the real thing.

There are also many similar civilian designs, for example the Firefly Series 3
http://relic-raider.com/firefly-series-3/firefly-series-3.html

This type of heliograph uses a retro-reflective disc to create an aiming "fireball". Here is a brilliant website that tells you all about retro-reflective heliographs:
http://www.bsaontarget.org/mirrors?tmpl=%2Fsystem%2Fapp%2Ftemplates%2Fprint%2F&showPrintDialog=1

 

[GM0WEZ]

I'm a parent helper for the local scouts, and conveniently we have two 3-400m hills about 5 miles apart. So I have sometimes wondered about actually trying this.

I'm told a compact disc DVD can be used in an emergency. You hold your finger up to the aircraft or whatever you're trying to signal, and look frough the hole to check the reflected light is falling on your finger.

 

[foggycoder]

Heliographs have always been popular with the Scouts.

You might be interested in Operation On-Target as a source of inspiration.
https://en.wikipedia.org/wiki/Operation_On-Target

 

[foggycoder]

Reading my previous posts, you might think that a double-mirror heliograph mounted on a tripod with a keyed shutter is the way to go. And certainly this was the method used by the professional heliograph signallers of the recent past (surveyors, military, US and Canadian forestry protection services). But the tripod heliograph does have one drawback - the sun moves...

Azimuth
Let's say the sun rises in the east and sets in the west, and the target lies due south. At sunrise our mirror will have to be facing south-east; at midday it will face south; and at sunset it will face south-west. The sun moves across the sky at 15 degrees per hour so we will need to move our heliograph at 7 degrees per hour. The beam is 0.5 degrees so, rather than move it continuously, we could move it 14 times an hour (every 4.5 minutes). However, the target would start and end at the extreme edge of the beam so we're probably looking at adjusting the heliograph in azimuth every couple of minutes.

Altitude
The sun follows an arc across the sky so it's change in altitude must also be accounted for. This will depend upon the latitude and time of year.

Charles Babbage (of early "computer" fame) had a go at a sun-tracking mechanism but it fell to the French to come up with a practical device.

 

[foggycoder]

This Heliograph thing has grown legs and is becoming close to an obsession! Just a couple more notes of interest though before I go quiet (for a while, anyway).

Dispertion
This is a characteristic of all heliographs. The reflected beam is not a tight laser beam - it spreads out with distance (0.5 degrees), and therefore the intensity of the received light reduces. A rule of thumb is that the maximum range [in miles] is 10 times the diameter of the mirror in inches. A lot of the modern survival heliographs are only 2 inches but this will therefore give them a range of 20 miles.
For moving targets at close range, the beam was deliberately dispersed (to 15 degrees) by a lens. This reduced the range but also reduced the likehood of the target moving out of the narrow beam.
Conversely, to prevent interception by military opponents close to the line of the beam, a beam narrower called a "snoot" was used, but this reduced the range considerably.

Night
Heliographs work at night too! The moon is used as a light source. Presumably this assumes that the moon is more than just a sliver of silver, and that it has risen when you need it. I must try this.

 

[foggycoder]

My first Heliograph! Given it's size, I'm calling this the "GO BIG OR GO HOME" heliograph. Actually, it's not that big compared to some heliographs you see. But it's a lot bigger than those 2" survival ones. The crews of the ships anchored off Torbay and the residents of Brixham are going to get familiar with a strange bright flashing light over on the horizon!

I buffed the silvered backing off a 2p piece-sized area with a brass wire brush on my Dremel. Amazingly, it doesn't scratch the glass. I punched a hole in a square of retro-reflective tape and taped it over the resulting hole in the silvering. That's it. No skill required.

I really couldn't understand the instructions on the internet for these aimers but as soon as you look through it, it all falls into place. The red "fireball" stands out very well so it's a very effective way of knowing where the beam is pointing.

PROS

• Cheap - the mirror in the frame was £2 from a charity shop; the red retro-reflective tape was £3 for a metre from eBay (far more than I'll ever need).
• It's big - at 13 inches, it's "rule of thumb range" is 130 miles. Given the reducing atmospheric attenuation with altitude, I should be visible from satellites in Low Earth Orbit! I don't think the guys on the ISS are going to be interested in a heliograph QSO with me though.
• The frame makes a good hand-hold.

CONS

• Being necessarily made of glass (you couldn't buff the silvering off acrylic without scratching it), it's quite heavy and awkward to hold. This will make it difficult for morse communications. It would be better if I fixed it relative to sun and target, then used a "table tennis bat" shaped paddle as a shutter. Or use a smaller lighter heliograph.
• It's difficult to move about unobtrusively whilst carrying a bathroom mirror. It's going to attract attention.

Yes, I could just have bought a heliograph for the same price, albeit not so big. But I enjoy making things and learning how they work.

I'm going to make a retro-reflective target (using white tape this time) for use at night (and maybe also during the daytime). More on this to come once I've had a go.

 

[GM0WEZ]

Do you have a link to the instructions for making DIY heliographs?

I would suggest a QSO but Scotland to Torbay on heliograph might be a tad ambitious....

 

[foggycoder]

Try this video:
https://www.youtube.com/watch?v=wh5MkBnsnfE

Personally, I think he should've worn gloves when cutting and handling the unfinished mirror. I'll probably be cutting my big mirror down at some point and I shall certainly wear gloves for that until I can get those edges sanded.

 

[Ham4CW]

Found this video entitled , "Signaling over 3 Miles (5 km) with a Mirror"

https://www.youtube.com/watch?v=am2hX36FaPc

I get the feeling you would need to be pretty accurate with your aim to attract the attention of a passing aircraft at 35,000 feet.

I believe military aircraft generally flew at much lower altitudes in the past, more like 2000-5000 feet, so more chance of being seen, especially if it was a rescue mission and the crew were actually looking out for signals.

73, Mark...

 

[foggycoder]

Interesting video (once you get past the fluff). It suggests that getting a nice steady beam might not be easy. And a steady beam is the necessary foundation of a morse code message. Once you've established that, you can interrupt it in an organised way to create morse.

I've made a 12" square retro-reflective target so I now have the means to get direct feedback on how my beam looks at the receiving end. I'll post the results when I have them.

 

[foggycoder]

US FORESTRY SERVICE - replacement for morse code - Boulden Code

By the early years of the 20th century, the US Forestry Service had big problems with morse code - there simply wasn't enough time for the look-outs, who were only recruited for the short fire season, to learn morse code. So, in 1916, they came up with an alternative code which proved to be much easier to remember and was so successful that it was widely adopted. Here's how it worked:

The letters of the alphabet (in alphabetical order) were split into six groups of six letters (that's easy to remember):
[list type=decimal]
[*]A  b, c, d, e, f
[*]G  h, i, j, k, l
[*]M  n, o, p, q, r
[*]S  t, u, v, w, x
[*]Y  z
[/list]
So, for each letter you wish to send, send the number of Long Flashs for the group the letter is in; then send Short Flashes for the position of the letter within that group.
For example, the word "pals" would be sent as
- - - . . . .
- .
- - . . . . . .
- - - - .

This code is easy to remember - you really just have to remember the six First Letters. And, even if you forget, it's easy to figure out.

GM0WEZ might find this easier for his Scouts than proper morse code.
One scout could look and say out loud the dashes he sees ("Dash, dash, dash"); another scout could then say the dots ("Dot, dot, dot, dot"); a third scout could look that up on the table, calling out the letter; and a fourth scout could write the letter down. Good group (patrol) activity.

 

[foggycoder]

WW2 Luftwaffe "Ziess Ikon" Heliograph

I came across this fab looking heliograph - just look at that engineering.

I'm trying to figure out how it works. I'm presently presuming that it's similar to a double-sided sighting system as used by the contemporary American General Electric ESM/1 and ESM/2 heliographs (see next post) but, I confess, the small angled mirrors baffle me.

 

[foggycoder]

WW2 US AAF ESM/1 Heliograph

Made by General Electric. A simple double-sided mirror with a cross-shaped aimer.

The instructions read
[list type=decimal]
[*]Hold this side of mirror close to face and reflect sunlight on any nearby surface in line with target. Tilt mirror to shine towards target.
[*]Look in this mirror for cross-shaped spot of sunlight coming through cross and falling on face, hand, or light-colored shirt.
[*]To surely hit target, keep it in view through center of cross and tilt mirror to move cross-shaped spot onto cross and target.
[/list]
Size
13 cm x 10 cm x 1 cm;
5 1/8 in x 3 15/16 in x 13/32 in

These were replaced by single-sided heliographs with the retro-reflective "fireball" aimers.

 

[Ham4CW]

US FORESTRY SERVICE - replacement for morse code - Boulden Code

By the early years of the 20th century, the US Forestry Service had big problems with morse code - there simply wasn't enough time for the look-outs, who were only recruited for the short fire season, to learn morse code. So, in 1916, they came up with an alternative code which proved to be much easier to remember and was so successful that it was widely adopted. Here's how it worked:

The letters of the alphabet (in alphabetical order) were split into six groups of six letters (that's easy to remember):
[list type=decimal]
[*]A  b, c, d, e, f
[*]G  h, i, j, k, l
[*]M  n, o, p, q, r
[*]S  t, u, v, w, x
[*]Y  z
[/list]
So, for each letter you wish to send, send the number of Long Flashs for the group the letter is in; then send Short Flashes for the position of the letter within that group.
For example, the word "pals" would be sent as
- - - . . . .
- .
- - . . . . . .
- - - - .

This code is easy to remember - you really just have to remember the six First Letters. And, even if you forget, it's easy to figure out.

GM0WEZ might find this easier for his Scouts than proper morse code.
One scout could look and say out loud the dashes he sees ("Dash, dash, dash"); another scout could then say the dots ("Dot, dot, dot, dot"); a third scout could look that up on the table, calling out the letter; and a fourth scout could write the letter down. Good group (patrol) activity.

That's a similar idea to the Smitty Harris Tap Code...

 

[foggycoder]

NIGHT HELIOGRAPHY using street lights

I was out in the park last night with the wife and the dog, trying out night Heliography. My kit consists of:

• 12" square mirror with "fireball" aimer. If anything, the aimer works almost too well at night - the red "fireball" is surrounded by a red line halo which partially obscure the weak reflection from the target. I might try an aimer with a bigger central hole (less tape visible), for night use.
• 12" square target - cardboard covered with white retro-reflective tape. And a wooden stick to hold it upright (at 90 degrees or thereabouts to the incoming beam).
• Torch - to leave by the target, pointing at the sender (otherwise you can't see where the target is 'cos its inky-blackers out there).

A white street light (one of the modern LED ones) is best. You need to stand a little behind it (so that the streetlight is between you and the target) otherwise the angle is too wide for the aimer to work.

I didn't measure the distance but I'm guessing it was a couple of hundred metres. The reflection from the target was weak but clearly visible (there are different qualities of retro-reflective tape and mine is the cheap stuff). The wife reports that the signal was very bright and obvious.

Morse Code is tricky, but the Forestry Service code (and presumably the Smitty Harris Tap code would be the same) was fairly easy. For dashes, put the "fireball" just to one side of the target and rock your upper body so that it swings onto the target, pause, swing back. For dits, swing the "fireball" slowly past the target. So, rock, rock, rock, swing, swing is N. It's going to be slow but it would probably get faster with practice at both sending and receiving. Unfortunately, my wife has no interest in learning the Forestry Service code.

I've taken my mirror out of it's wooden frame so the weight has gone down from 2 kgs to 700 gms - that's a big improvement.

I will now try the reflector in the daylight and report back.

 

[foggycoder]

NIGHT HELIOGRAPHY more

I've had another night in the local park. There were a lot of dog walkers. Every dog walker with a torch (which is every dog walker) went over to my reflector to investigate the strange object glowing in the dark. I was just hoping none of their dogs would wee on it!

It's difficult to hold the mirror beam on the target, point my phone camera through the aimer, and press the shutter release, all at the same time. And the camera struggles to focus properly when pressed up against the back of the mirror. But below is an image to show you what the "fireball" looks like at night.

The original "fireball" was fairly bright at night and tended to obscure the weak reflection from the target so I made another aimer just for streetlights, with a bigger Pupil (centre hole). This was a success - it's now easier to see through the aimer over a wider angle, and the fireball doesn't obscure the target as much.

Having tweaked the night aimer, I've also modified the sun aimer by increasing the size of the Iris (the retro-reflecting area around the Pupil). This, too, has been a success - the "fireball" is brighter, and visible over a wider angle.

I've included an image of both aimers side-by-side so you can compare the relative sizes. The diameter of the sun aimer is 30mm; the diameter of the night aimer is 23mm. Sorry about the fuzzy image - unsurprisingly, my phone struggles to auto-focus when pointing at a mirror (it uses an infra-red sensor to measure distance).

 

[foggycoder]

HELIGRAPH REFLECTOR in the daytime

I've just tried out the 12" square retro-reflector. With it placed in shade and standing 200m away, the image below simply doesn't do justice to how bright it is - it's really VERY BRIGHT! Almost as bright as the sun (which is what you'd expect given a mirror reflectivity of, say, 90% and the target the same size as the sun beam). Crikey, it's bright.

The only slight issue is that the "fireball" is also very bright and totally obscures the reflection from the target if you're looking through the aimer. I could see how bright the reflection from the target was because I steered the sun beam using the aimer until it was on the target and then peered around the side of the mirror to see the target directly. But that's rather awkward unless you've got a very stable platform for the mirror.

There's no problem if there's an observer/operator at the other end and you know where he's standing - you just use the "fireball" to point at him. But now I have some idea of just how bright a 12" heliograph can be at close range!

 

[foggycoder]

Yes, indeed. The moon is next. I'm waiting for the 23rd October when the moon is half full and then I'll have two weeks in which to work with a reasonably bright object. Fingers crossed for some clear autumn nights.

Needless to say, I'll post the results here.