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.

481 THz testing

If this photo has been on recently, please accept my apologies. 

For some reason, my XYL laughs when this appears. As a geek, I cannot understand why!  😉

It is some time since I did any serious work at optical frequencies. With the dark evenings I really should try.

481 THz RX

 

This is me resurrecting some 481 THz optical gear.

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.

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. 

481 THz tests

I have resurrected my optical gear. It had stood largely unused for 10 years.

As yet, I have not got Spectran working with the optical RX so I can only do optical tests with continuous carrier or CW and not QRSS. Tests so far are a reflected (off a wall) signal on CW. Good copy over a reflected path of just 100m. At least the optical gear works again!

UPDATE 2020z:  Expections were well exceeded. I set up my 481 THz beacon firing out of our lounge double-glazed window at a wall of a house at the very far end of our close. I walked with my RX to the other end. So the path distance was about 0.25km with one reflection. Signals were S9+ even by ear. The gear really works well. I must get Spectran working and try some NLOS tests. with G4HJW. I suspect we will have greater success with cloudbounce. My main issues are exhaustion and giddiness.

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

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.

481 THz optical experiments

It is many years since I used my optical gear. As mentioned previously, I want to check it all works, download Spectran 2 and do some local tests initially. Our local church is about 300m away, so perhaps I can do some QRSS tests bouncing off this? 

It the local tests work, I would like to do some over the horizon tests with G4HJW who is about 10km away. Sadly, there is a lot of clutter locally, so perhaps I would have a better chance with Bernie using cloudbounce, rather than clear air scattering? He might have to point to higher in the sky. With passing clouds, I might well copy him.

Being far more wobbly these days, this will be far harder for me now.

All my 100mm gear is still in the shack, but it all needs putting together and testing.

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.

481THz tests

These days I am just too wobbly to do optical tests "out in the field". However Bernie G4HJW has offered to put up an optical beacon so I can see if I can copy it "over the horizon" 10 miles away at my QTH. It is many years since I did optical experiments and this will be a challenge on many levels. 

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. 

481 THz optical communications

Before my 2013 stroke, I used to do a lot of portable tests on optical communications. My favourite activity was over the horizon optical communications. I was surprised to see my beacon even when nothing could be seen in the sky. On the PC, the signal was very clear.

What is good is that equipment is homemade as well as the testgear.

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

Geek?

OK, I admit it. I am a geek! 

This was me in 2013 testing my 481 THz optical kit in the garden. I don't think the neighbours were looking.  😁

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