481THz QRSS3 beaconing across the garden

Last night I fired up my 481THz optical kit with poor results: I think the RX unit may have a flat PP3 battery? On the Spectran display the QRSS3 signal bounced off trees and bushes should be very easy to spot, but for an unknown reason, I was struggling.  I shall recheck all the kit today. The kit has to be well focused and working well to work DX non line of sight (NLOS), which is my plan soon.

My stroke symptoms (poor balance and clumsiness) are really not helping: tasks that were very easy last year are very hard this, well at present they are.  Before my wife and I venture out into the dark fens, I want there to be a good chance of success, which means good and thorough preparation.

Optical Comms in Vancouver Canada

This morning I received an email from Steve, VE7SL, reporting on his experiments with VE7CA over a 2-way distance of 54km using red LEDs.  They are doing really well and Steve is writing an article for a Canadian journal. They seem to have been encouraged by my own modest efforts,which I hope to restart before too long. At present my poor fitness and temporary inability to drive because of the stroke are real handicaps.

Image of optical path spanned from VE7SL

Source of BRIGHT red LEDs

Some have asked me what LEDs I've been using so far for my optical experiments. Well, these are 10mm diameter "conventional" style LEDs from a source in Hong Kong. They are 1W devices capable of 280000mcd output and look like a normal LED on steroids in that they come in a standard looking clear package with 2 thick leads.

They are available via eBay at £9.30 for 10 off from Hi Tech LED World.  The supplier delivers promptly and with good packaging (and a nice collection of attractive stamps on the package). They also have a range of other devices available.

Use the link http://www.ebay.co.uk/itm/350347623711 .

As mentioned before, I also have some even more powerful LEDs called Phlatlights which are intended for overhead projectors. I've still to fire these up. These are about 10dB more powerful than the 1W LEDs, so are potentially dangerous.

My first 481THz 2-way QSO

The 481THz kit at the G3XBM/P end of the path

This evening, thanks to Bernie G4HJW, I managed my first 2-way optical QSO over a path of around 10.5km.  For the AM baseband QSO, Bernie used his Finningley transceiver with 100mm optics and I used my simple AM TX  with my modified KA7OEI receiver with unbiased BPW34 connected directly to the FET gate.  For some reason, the RX in my dual tube transceiver (the one on the larger tripod) was about 3-4dB less sensitive than the separate RX, so in the end I used this to copy Bernie at a solid 58-9 with scintillation.

Successful 481THz NLOS test (8.63km)

8.63km non line-of-sight reception of 481THz optical beacon

Bernie G4HJW set his high power optical beacon running a 1.082kHz tone this evening pointing in the Burwell direction on a non line-of-sight path from his home QTH at Little Wilberham. He then came over to Burwell to compare his RX and my own from a test site on the edge of the village clear of the village lights. Distance was 8.63km.

Both on Bernie's RX kit and my own we got solid copy by ear of the beacon at a distance of around 8.63km NLOS using 100mm optics. Once found, the signal was solid.  I then set up the optics on the tripod and fed the signal into Spectran where the signal was 30dB over noise in a 0.17Hz bandwidth. Listen here for a recording (best played back using Spectran with 0.17Hz bandwidth settings)

G4HJW's beacon TX

There was hardly a cloud in the sky, so this was largely by scatter from the mist/dust in the air. Bernie says signals have been stronger on other nights. Best reception was with the RX aimed just above the horizon, maybe 5-10 degrees at most above.

This was very gratifying as it is the furtherest NLOS signal I have copied and it verified my RX kit is now working at good sensitivity.

When I got back home I did try to copy the beacon by ear out of the bedroom window but the tree cover and lights made copy not possible. However I will try again later in the week with Spectran running and narrow bandwidth.

Optical cloudbouncing (stage 2)

With my QRSS3 success last weekend over a 3.6km non line-of-sight path at 481THz (red light) I've been looking at other possible NLOS cloudbounce paths that start from my home QTH where I can set up my 100mm optics 0.7W input beacon pointing out of a bedroom window.

There are several different paths out to around 8km away that will be tried shortly.  I need to do a quick check at the RX locations to see that there are no issues e.g. trees very close and that I can safely park the car off the road at night. The tests can't start for a few days as I have grandchildren with us over the weekend. Maybe the first test will be on Tuesday evening.