481THz optical beacon

 

One of my Facebook memories today was this photo of my 481THz optical beacon. This was made in 2012 I think. 

I still have it and hope to use it again. It uses a K1EL keyer to produce either CW or QRSS. My first test is likely to be some sort of reflection test, possibly off trees.

It seems I like to experiment at the extreme ends of the spectrum, HI.  Either VLF (sub 9kHz) or optical comms (481THz)!

Optical Communications

It is many years since I tried any optical communications, because of my poor health:  I have been too giddy for field work.  

Hopefully, the next few weeks will allow me to do some local tests from home.

See https://sites.google.com/site/g3xbmqrp3/optical

481THz experiments

Many years ago before my 2013 stroke I bought some Flatlights (very bright LEDs) from the USA to enable me to get further with my optical experiments over the horizon. Even with quite low power LEDs I had got way over the horizon. 

Both my RX and optics could have been improved, so I was expecting much greater ranges. Then I had my stroke and I was unable to continue. To this day the Flatlights remain in the drawer unused.

Optical communications

Optical RX

Until my stroke in 2013, one of my joys was building and testing optical communications gear. Although I had a successful line-of site speech contact, my "thing" was weak signal communication over the horizon.

Even without any visible signals in the sky I was able to detect my beacon from home on 481THz (red optical) way over the horizon, even though it was firing through double glazing. Had I been able to carry on, there were so many things I wanted to try including higher powerLEDs, further distances and a better tripod.

Sadly, these days I am too wobbly to do this portable work. As all the gear can be built and tested in the "back of a garage" with simple test gear, this could appeal to those interested in serious, but low cost, experimentation. Over the horizon optical work could do with attention.

See https://sites.google.com/site/g3xbmqrp3/optical

Modulated light communications

When I was fit and healthy, I enjoyed experimenting with over-the-horizon optical communications using homemade kit and free software. As I recall my RX was based on one from the website below. Personally, I found optical communications more rewarding than microwaves. All the gear was homemade, including the optics and test gear. It was inexpensive and one was working "at the frontiers". Not forgetting the most important thing - it was fun.

See http://www.modulatedlight.org/optical_comms/optical_index.html

See also my own page at https://sites.google.com/site/g3xbmqrp3/optical

Good optical comms site

On my own main website is some information (now very dated!) about my own experiments with optical communications at 481THz (red light). I was mainly interested in over the horizon, weak signal modes.

I was quite amazed to clearly detect my optical beacon over the horizon when nothing was visible in the sky. There were no clouds so I assume this was clear air scattering off dust particles.  This was using QRSS3 and a PC to "see" the signal. My own experiments stopped shortly after my 2013 stroke. I did try one experiment out portable since, but I was too clumsy. I have not tried anything portable since 2014.

All the gear needed is quite simple to make and all the test gear needed easy to fabricate. I made a very weak signal source using a very very dim LED to test the receivers. This was mounted near the ceiling of a darkened room. With a good RX this should be received OK. If you cannot detect modulation on a very dim LED your RX is not good enough.

I still have all my optical kit. If anyone local wants to borrow it to carry on the experiments, I'd be very happy. They must be local as I will want the gear back.

Another good resource is http://www.modulatedlight.org/optical_comms/optical_index.html

Optical DXing

Since my 2013 stroke I have not felt fit enough to do field work. I really miss my 481THz over the horizon NLOS (non line of sight) optical work.

Testing the optical kit

The results back in 2013 suggested much further would have been possible NLOS. All the gear was home made and the experiments were fun. Sadly I am just too wobbly these days.

It would be good to try infra-red frequencies. What amazed me was the total lack of a visible signal, yet perfect decode using QRSS3 on the PC on a very non line of sight path over the horizon.

See https://sites.google.com/site/g3xbmqrp3/optical
See also https://sites.google.com/site/g3xbmqrp3/optical/481thz-nlos

Optical kit

One of my Facebook memories today is of testing my 481THz optical kit in the garden of the old QTH. In those days I was fit and well. These days, field work has proved impossible although I still hope to restart one day. The photo is here as a reminder (to me!).  And, no, I was not looking at that attractive girl up the street!

All the optical kit was homemade and easy to assemble and test in the back of the garage with very basic test gear. Even the software used was free. Over the horizon testing with optical kit was challenging and great fun. Results amazed me.

See https://sites.google.com/site/g3xbmqrp3/optical

Optical Communications

One of my favourite things before my 2013 stroke was experimenting with optical communications. I had some success with "over the horizon" weak signals.  No sign of the red light was visible, yet it could be detected miles away non line of sight (NLOS) with a laptop. These days I am just too wobbly to do this.

As I have said before, test gear is easier than microwaves and all the kit can be made in a shed for very little money. This is an area rich for experiments and right at the frontiers.

See https://sites.google.com/site/g3xbmqrp3/optical .

Optical NLOS work

One of my interests before my 2013 stroke was optical communications over the horizon - non line of sight (NLOS).

Although I briefly tried a few years ago, I was still too wobbly, so had to give up. Sadly, I still feel giddy when on my feet, so further optical experiments are on hold for the time being. Others have continued the work and one thing worth trying is using infra-red, which many say is better for NLOS than red LEDs.

At some point I do hope my health improves so that I can resume these tests. Test gear is simple (easier than microwaves) and this really pushes the boundaries - true experimentation.

Optical comms at 481THz

It is some years since I last tried optical communications. This has been because of my poor health. 481THz is easy: all gear was home made and test gear is simple. In most ways nanowaves are easier than microwaves. My "speciality" was non line of sight (NLOS) using digital techniques. I also had one 2-way optical QSO over about 11km. Then I had a stroke and everything stopped!

My experiments used low cost red LEDs. At some point I'd like to try infrared. My tripod was low cost. A better one is really needed as aiming is important.

See https://sites.google.com/site/g3xbmqrp3/optical .

Optical Communications

It is some years (before my stroke in 2013) that I last tried seriously with optical communications using red LEDs that I bought at low cost via eBay. These days, I expect a google will bring up lots of links. This is a fun branch of our hobby, with very low costs and lots of homebrewing. This is a branch of the hobby I'd like to try again. There is much to learn.

See https://sites.google.com/site/g3xbmqrp3/optical .

481THz NLOS (over the horizon)

Before my stroke in 2013 I enjoyed building and operating optical communications gear. My stroke has rather scuppered this, for now! Although I had one over 10km line-of sight speech contact with G4HJW/P, my main interest was weak signal, over the horizon, communication. I did tests at over 8km non line-of-sight using QRSS3. Although there was no evidence of the optical signal in the sky, the QRSS3 signal was clearly decoded on the PC at the receive end. Overall, I was left with the impression that much further would have been possible.

At some point I really want to continue this work. All my optical gear was home-made using material that was low cost and easily obtained. Test gear for optical work was simple and low cost too. In my view, optical work is more rewarding than microwaves and the test gear simpler.

See https://sites.google.com/site/g3xbmqrp3/optical

481THz over the horizon

Facebook reminded me that 4 years ago I was doing QRSS3 tests with light at 4.8km over the horizon.

"Much better results this evening with 481THz light beam signals over the horizon at 4.8km. Last night I was 2.5 degrees out and signals were much weaker. Tonight QRSS3 could be comfortably copied at 20dB S/N in 0.34Hz bandwidth. At the receiving end the signal is not audible and nothing visible in the sky from the transmitter. Aiming is VERY critical just above the horizon."

Lightwave Comms

Because of my poor health I have not been able to pursue 481THz (lightwave) experiments especially "over the horizon" NLOS tests. Thankfully, others are "carrying the torch" .

See http://qsl.net/ve7sl/westcoast%20lightwave%20project.pdf

241GHz or optical?

Although the world record for DX on the highest microwave band (241GHz) allocated to radio amateurs is measured in several tens of km, the UK record is quite modest.

My own view is 481THz optical is much easier: test gear is trivial and all the gear can be made inexpensively by nearly anyone. Microwave gear is much harder. I know people say you can "do microwaves" with minimum test gear, but I think you will find most who are successful are, or were, in the business professionally and have access to good microwave test gear. With optical gear this is definitely not the case. Before my stroke I built all my optical gear in the back of a garage and I achieved very useful results. Others have achieved far more than me. All you need are a scope, a multimeter and an audio generator. Much of the test gear needed for optical work is freely available software on the internet.

See http://www.microwavers.org/?241ghz.htm .

481THz test

The wind is soon to be light and from the north and east. This means our windmill sails will be out of the way if I manage to do some optical tests in the next few evenings. I want to see if I can detect my 481THz red light reflected off the windmill using QRSS3 at a moderate distance.

To do this test I shall need to aim my QRSS3 optical beacon at the windmill and use a PC with Spectran software and sensitive detector and optics at the remote site. I have tripods but they are not the world's best.

As it is some time since I used the gear, I need to do some local tests first to check all is well.

Optical work is fun as all the gear is homemade and test gear is simple. In my view this is more fun than microwaves. It is accessible to all. All you need are a weak light source, a scope, free software and a multimeter.

In my healthier days I had a lot of fun detecting my QRSS3 optícal signal over the horizon  There was no sign of the signal visible by eye, but on the PC screen it was very clearly visible.

See https://sites.google.com/site/g3xbmqrp3/optical/481thz-nlos .

481THz lightbeam experiment?

Our local windmill. Me seated. XYL on RHS.

It is getting close to the time when I fancy some field work! My first experiment will be to detect QRSS 481THz (red light) at some distance by reflection off our local windmill. It will need my XYL to accompany me as it will involve night driving but it will either work or not. This will be my first field test in a long long time.

This picture was taken in 2014 and the laurel hedge has grown quite a bit since. Look at a later post to see how it looks now.
Small steps...

Optical communications over the horizon

I have been too unwell to do this recently, but not long before my brain bleed (Sept 2013) I was amazed at optical communications over the horizon, non line of sight (NLOS) using clear air scattering.

The inspiration for all my optical experiments came from Stuart Wisher G8CYW who did a great series in RadCom a few years ago.

Testing optics

My home made transmitter only consumed about 0.7W from a red LED bought on the internet. My homemade RX and TX used homemade optics based around cheap drain pipes and cheap magnifying glasses. The whole RX and TX were simple and low cost. Only simple test gear was needed too. It is a bit like microwaves, but easier to build and test.

There was no sign at all of the TX beam in the sky.  All alignment used dead reckoning with some panning at the RX end to find the TX.

Using free PC software and QRSS3 helped as bandwidths as low as 0.37Hz were possible.

When fitter I want to try infra-red LEDs instead.

See https://sites.google.com/site/g3xbmqrp3/optical/481thz-nlos.

Optical testing - too easy?

Before dark, I tried TXing from one side of the house to the other reflecting my 481THz optical beacon off the windmill. Even by ear in 600 ohm phones the signal was very clear and very easy to find. This was only about 100m path length, but I wanted to check the gear still worked as it is a long time since I used it. Not sure what to try next as I still feel very wobbly on my feet and tire easily. At least I know my homebrew optical gear all works still.