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.

Sunspots and 10m propagation - Monday May 25th 2015

Sunspot count is 74 today (K=1) but 10m propagation is again expected to be "poor".

UPDATE 1253z:   So far today, apart from a couple of locals on 10m, only CT1JTQ (1843km) by Es. No DX seen, well not yet, on 10m WSPR.

UPDATE 1834z:  A little Es and single hop F2 spots from EA8BVP (2986km) but no "real" DX on 10m so far today.

Flotta Island IOTA

Southgate Amateur Radio Club News reports that the Orkney Amateur Radio Club is activating Flotta Island in the Orkneys mid July. I am not a great DX chaser, but I can understand the motivation behind IOTA. Of all the DXing activities, this is the one I could imagine doing.

See http://eu009.webplus.net/ .

Grandchildren this week

Over the next week, we have both sets of grandchildren staying with us. For the first half of the week, my shack houses a travel cot so I have far less access to the amateur radio gear and PC.  I hope to remain on 10m around the clock ( PC only needed to sync the clock) but my access to 6m will be much more restricted. Although tiring, the grandchildren take priority.

UPDATE 1945z:   Es (and EA8BVP via F2) on 10m WSPR during the day, but no Es evidence here on 6m WSPR where only G stations have been spotted and spotting me.

UPDATE 2052z:   EA8BVP (2986km) spotted my 500mW 10m WSPR beacon 21 times today, so far.  I presume these were all single-hop F2.

6m WSPR this morning

So far today, only G stations spotting me and being spotted on 6m WSPR.  No Es seen yet on the band. G3ZJO (79km), G0LRD (25km), G8EPQ (77km), G0OQK (98km) and G4APB (88km) so far in the 6m WSPR logs.

W5OLF WSPR beacon

W5OLF - WSPR-AXE-CW beacon

There are other solutions around for WSPR (like the Ultimate 3 kit from Hans Summers - excellent I am told) but I have had Wolf's 10m 500mW,  fully stand-alone, WSPR beacon (WSPR-AXE-CW) running more or less continuously for 6 months now. This fits in a small Altoids sized box and needs no PC at all. The frequency is randomised but always on TX. My antenna is a 3 band low wire and certainly not the best for 10m. Despite this, it has been copied in the USA most days for months and has been spotted in every continent on the planet including Antarctica and Australia. If I am around, the 10m WSPR beacon is usually on. If you are after a fully stand-alone WSPR beacon for 30m, 20m or 10m these beacons are on a single PCB and work well. As the photo shows, the board is simple and the kit comes with a pre-programmed chip with your callsign, locator and power ready for use.

See https://sites.google.com/site/g3xbmqrp3/hf/w5olf .

Sunspots and 10m - Sunday May 24th 2015

Sunspot number today is 69 (K=2) and 10m propagation expected to be "poor".

UPDATE 0905z:   EA8BVP (2986km) was again spotting me very early on 10m WSPR. I presume this is F2. Otherwise just local G4IKZ (18km) spotting me. No real DX spotting me, well as yet!  Always hopeful, even though the 10m forecast is "poor" today again.

UPDATE 1038z:  CT1JTQ (1843km) spotted me a couple of times recently by Es, which appeared about 20 minutes ago here on 10m WSPR.

Overnight surprise on 10m

At 0132z I was spotted by CT1JTQ (1843km) on 10m WSPR. I assume this was an isolated Es opening, but was surprised by the time, which was the middle of the night. The beauty of WSPR! Leaving WSPR running whilst getting on with other things is certainly a good idea. How else would such a fleeting 10m opening,  in the middle of the night, be noticed? 

This is especially true on 6m where WSPR should allow short openings, often at odd times, to be noticed and recorded. Often short openings can be missed.

How simple?

Some years ago I attempted to see how few components were needed to communicate on 10m. The Lesser Chirpy was the best I could manage. This was a derivative of The Chirpy, which worked, but had far too much chirp!

Looking at the circuit I see I could save 1 component by replacing C1 and C2 by preset C's and shorting out C3. This would allow the TX-RX offset to be set. If one was made a variable rather than a preset the RX-TX offset could be adjustable.

Since being ill I have not tried the rig. A limitation was the limited RX sensitivity, meaning only stronger stations would be workable.  However, the rig does work and is very simple. Another possibility is to switch to an external RX but allow the internal RX to be used when signals are strong enough. The TX power is certainly enough to span the Atlantic and work all over Europe.

The secret to low chirp on 10m is the use of FSK rather than CW. Essentially the TX changes frequency rather than go from RX to TX every time. This means full break-in is not possible in such a simple circuit. Can you do better? If so, I'd love to see the schematic please. I make no great claims for my circuit, which is an amalgam of ideas. Pure fun!

See https://sites.google.com/site/g3xbmqrp3/hf/chirpy .

6m Es

EA1KV (1304km) has spotted me twice, so far, on 6m by Es.  I am sure there many be other Es stations this lunchtime and teatime on 6m WSPR.   Apart from this Es opening, all spots (given and received) have been G stations - G3ZJO (79km), G8EPQ (77km) and G6IMT (65km).

UPDATE 1600z:  Teatime and the Es is back again on 6m.  EA1KV (1304km) is again spotting my 1W ERP on 6m WSPR.

UPDATE 2002z:   No further 6m Es WSPR spots seen here this evening.