Over the horizon on 481THz (optical)

Before my 2013 stroke I enjoyed experimenting at optical frequencies and was amazed that I could decode my QRSS CW well over the horizon with no clouds in the sky. Sadly, my stroke put an end to this. The circuit diagram shows the beacon I used. As you can see it is simple.

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/over-the-horizon .

Optical DXing over the horizon

Some years ago, when I was fitter, I really used to enjoy going out in the car to experiment with non line-of-sight optical beaconing. I would set up my beacon at 481THz on my windowsill indoors and see if I could copy it over the horizon. Sadly my stroke ended these tests.  

The photo shows my beacon, that was connected to 100mm drain pipe and a Poundland lens.  The LED was bought off eBay. Latterly I bought some much brighter Phlatlights, but I never got around to using them before fate intervened.

I was always amazed how well my tiny signal was copied over the horizon. I presume this was clear air scattering as there were no clouds.

2012 optical experiments

Way back in 2012 I was doing optical work at 481 THz. 

The photo shows some initial tests along the road at the old QTH. 

Later, some tests were done "over the horizon" non line-of-sight. I was astounded by the results.

Optical Experiments

One of the fallacies going around is that optical communication is just "line-of-site" and that both the TX and RX have to be able to see each other. This is just not true! 

With very low power and simple, homemade, gear I could detect my beacon on a PC way over the horizon. In Australia, the "over-the-horizon" (NLOS) distance record is way over 100km. With my own very modest gear, I can well believe this. 

My tests were done on cloudless nights, suggesting the propagation was scattering off atmospheric dust. There was no sign of the light from the TX in the sky at all.  This is definitely where everyone, licenced or not, may experiment. It would be good to find out how far we could achieve non line of site (NLOS) in the UK. Incidentally LEDs are generally considered better than lasers due to scintillation (look it up!).

My own beacon and optical gear were made in the back of the garage. If I was fit, I would be experimenting now.

My optical gear used LEDs bought off eBay. Far more powerful ones are available. I used 100mm lenses used in magnifying glasses bought at Poundland. Better equipped stations used Fresnel lenses. My tripod was hopeless. With better LEDs, lenses and tripods, ranges could be increased a great deal. Even with my system ranges could be considerably greater than the nearly 9km I managed.

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/over-the-horizon.

Optical communications - over the horizon

When fitter, I really enjoyed experimenting with this. Actually, I don't think this needs a licence at all, but it is real experimentation. Anyone can do this without costing much. 

All my gear and much of my test gear was homemade and very inexpensive. It is real "back of the garage" stuff. All my gear was homemade in the back of the garage. The only special test gear was a very weakly lit LED. If you have a multi-meter and scope, you really don't need much else. In my view optical communications is easier than microwaves as the test equipment is easy.

I was quite surprised how easy it was to copy an optical signal "over the horizon".

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/over-the-horizon . 

Plans for Monday

My 481 THz test software and lead are my priority. When I did the optical tests way back more than 10 years ago PCs had separate mic and headphone jacks. All my PCs now have combined jacks! 

So, I have to interface my optical RX and the PC in a new way. With soldering skills very hard these days, this requires some thought. Years ago I would just have bought a new jack socket (with mic input) and just changed the plug! I think years ago I just used a lead with standard 3.5mm plugs at each end.

I may put the 10m WSPR beacon on too.

UPDATE 1038z: 10m WSPR beacon is ON and my audio setup (interface from 481 THz RX to the PC) is working with Spectran. At G1KQH's suggestion I used a USB sound card I already had and it worked first time. Thanks for the suggestion Steve. 

UPDATE 1144z:  No 10m WSPR spots of my 500mW beacon. I suspect things are very disturbed. I checked all was well on another RX.

UPDATE 1515z:  4 stations have spotted me today so far on 10m WSPR. My 481 THz TX beacon and RX work with QRSS and Spectran. 

481THz optical beacon tests

This popped up as a Facebook memory yesterday. It is some years since I last did optical tests over the horizon. In the near future, I want to re-assemble my optical gear and do some local tests before attempting some NLOS tests with Bernie G4HJW who is over the horizon about 9km away.

Upcoming optical tests on 481 THz

It is years since I did optical experiments. My current plan is to do some local tests with QRSS bouncing off buildings. If these are successful, I want to try an "over the horizon" test with G4HJW. 

My first task will be to install Spectran 2 software as this will be needed to decode QRSS and to check the signal margins.

Early optical experiments

This was a whole 11 years ago. Later, I went on to much further over the horizon.

481 THz "over the horizon" communications

Since my 2013 stroke, I have felt too wobbly to do field work. One of my great pleasures was trying optical communications over the horizon where I was astounded by what was possible, even though there was no sign of any light visible. Had I been fit, far further would have been possible.

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/over-the-horizon for some ideas. 

In many ways optical communications are easier than microwaves as all the gear (test gear and working kit) may be homemade at low cost.

The photo shows my first tentative steps in daylight along a road. Little did I realise what fun was to follow!

Optical experiments

One of my Facebook memories today was an ARRL publication of 2019 called "The Proceedings of Microwave Update 2019" in which I appeared on page 25 with an optical receiver that someone else had used. 

My optical tests were great fun. They all happened before my 2013 stroke. I can recommend optical experiments to anyone, as all the gear for use and testing was homemade easily in the back of the garage (literally).

If that darn stroke had no got in the way, I should probably still be doing optical tests today!

Optical communications 2012

10 years ago I got 3 phlatlights from the USA with the intention of doing more "over the horizon" (NLOS) optical tests at 481 THz. Then my stroke got in the way. There are 3 in the drawer unused. 

Lightbeam communication

This was much easier than I thought. 

Although my "thing" is NLOS (non line of sight) over the horizon digital comms, I have tried line of sight speech communications. People have managed much further than I have.

One of the beauties is the gear is all homemade. Even the test gear was homemade and simple.

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/line-of-sight .

Optical experiments

In view of my earlier post, it is probably a good idea to point you to my pages on optical communications. I have not been able to do much in recent years because of my stroke, but there is nothing stopping others!

This is an area where the gear is easy, results can far exceed expectations and anyone can join in. As far as I know, no licence is needed.

All the gear uses low cost parts and can be assembled and tested in the back of the garage. Even test gear can be very simple and low cost. This really is great fun.

Some like to experiment with speech over very long distances. My "thing" was over the horizon. I was totally surprised that even when there was no sign at all of a signal, it could clearly be seen on a PC. The distance records for "over the horizon" are amazing. I think these used "cloud bounce", where signals are reflected off the base of clouds. In my case there were no clouds, so this was by refection off dust in the air I think.

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/over-the-horizon .

Early 481THz experiments

This photo popped up as a Facebook memory today. 

It shows my early trials trying to receive my 481THz optical CW beacon in daylight along the road. As I recall, signals were very strong. Much much further was achieved later including over the horizon (NLOS). 

I guess this was 2012? The gear still exists and still works. It has not been used much since before my stroke.

Optical communication webpage

In the past, I got lots of information from Clint KA7EOI's Optical Pages, that have many links.  One of the most sensitive receivers by K3KCP was linked to from Clint's optical pages.

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/over-the-horizon .

481THz test

OK, these are tiny steps. Yesterday I did a test reflecting my optical beacon from the kitchen, off the museum roof, to the RX in the lounge. I would guess the total path was only about 0.2km. The reflected signal was extremely strong, so I might try receiving the reflected signal at my son's house further away.

Unlike many years ago I am extremely giddy now. At one point the TX crashed to the floor. Luckily, nothing was broken.

I am just too wobbly for field work, but I want to do what I can. Receiving 10wpm CW at my son's house would be a great achievement for me nowadays.

Phlatlights

In 2012, I bought several of these from the USA. My intention was to use these very powerful LEDs in my experiments with 481THz light communications over the horizon having had great success with QRSS over the horizon with far less powerful LEDs. 

Then I had my stroke and I was just too wobbly for field work. They are still in the shack drawer! It would be great to use these as I am sure much further non line-of-sight would be possible.

Internet over free-space optical - NOT amateur radio

The BBC has an interesting piece about the use of free space optical communications to bridge the River Congo in Africa where optical fibre is impractical. This gives very high (not perfect) reliability and, in this case, is destined to carry internet traffic. Of course, this would not be suitable for places where fog is common, such as the bay area of San Francisco. 

See https://www.bbc.co.uk/news/technology-58583600 .

Optical 481THz line of sight

It is some years since I seriously worked on optical communications. My main "thing" was over the horizon, so called non-line-of-sight (NLOS) beaconing. I was surprised that with very simple, homemade gear I could get well over the horizon, with no clouds to help. If my poor health had not got in the way, I am sure far greater ranges would have been possible. The record (in Australia I think) is an incredible distance.

I only had one speech contact over 11km line of sight and that was with G4HJW. All my gear was made in the back of the garage and it was very simple. The optics used low cost PVC drain pipes and the lenses were made from magnifying glasses obtained from a local Poundland store. The electrical gear was very simple and low cost. It was not worth making PCBs. Test gear is very simple. Optical experiments are low cost and fun.

My main G3XBM website has much more on my gear and experiments including NLOS tests.

See https://sites.google.com/view/g3xbm4/home/optical-nanowaves/line-of-sight .