23cm - partial success

Although I got no FT8 decodes, my 23cm QRP signal did make it to the QTH of G4HJW, despite double glazed windows, bushes, a shed and 2 hills! I am sure on a less obstructed path I would succeed. Tomorrow I have a USB sked with G6UW in Cambridge.

The second photo shows the 2 element antenna firing through the shack window.

50W red LEDs cheap on eBay

Bernie G4HJW recently posted to the UK Nanowave Yahoo about some powerful red LEDs that he bought from China for just £2.80. A couple of these are more powerful than the 10mm LEDs that I used in non line of night tests (when I was fitter) but even without any lenses!  It would seem these would be ideal for optical tests. 50W is a lot of power. This was Bernie's post. I trust he won't mind me sharing it with you all:

"Morning all - This might be of general interest:

I recently bought a couple of 50W red LEDs from China, which I thought I might use in a wide-angle initial set-up lantern for portable use. They were very cheap (£2.80), so I also expected there would be dead segments, which there were, but there was a bigger surprise waiting to show itself.

During this weeks UK uwave group net, Martyn G3UKV asked me how wide the spectrum was, so out came my trusty secondary school Spectroscope. Instead of the expected relatively narrow response, there was noticeable output right through to yellow plus a weakish narrow line at the violet end. This should have been an obvious clue, of course, but it was only later when I was telling Stuart G8CYW (sorry about all the name dropping..) that he suggested  that the LEDs might be fluorescent driven devices, just like the white lighting LEDs all seem to be these days. He was correct, as the following picture shows:

http://www.earf.co.uk/uvred.JPG

Note that in pealing back some of the fluorescent gell, all but one of the individual 1W UV leds have been destroyed. Not obvious from the picture is that these LEDs are embedded in an initial clear silicon rubber prior to the red fluorescent layer being applied. From supplier ebay pictures, it is now clear that the same UV driven devices are available in all colours, leading to the question - does this produce an overall increase in efficiency, or is there simply a significant cost saving in just fabricting UV LEDs?.

I've yet to measure the response time of the fluorescent material.

Bernie
G4HJW"

Working with simple optical gear was one of my great pleasures, so I very much hope I can do this again. Optical gear is easier than microwaves. All my kit was home designed and built and the test gear simplicity itself.  For details of my optical work see http://www.g3xbm.co.uk  . G4HJW and others know far more than me in this area. I consider myself very much a novice in this area.

Finningley optical transceiver working fine

Although I posted this on the Nanowaves Yahoo group , I forgot to update folks reading this blog on the progress with this optical transceiver kit designed by Bernie G4HJW.

Well, at the weekend I finished building the unit and started testing it. The TX part worked first time, but the RX did not. Time to find out why!

Using logic and common sense, I carefully went through the various stages (8V regulator, later audio stages etc) and tracked the fault down to an intermittent preset SMA pot that sets the FET bias. The FET stage is the very high impedance stage that follows the PIN photodiode.

The error was entirely my fault and easily fixed by removing the part and redoing the surface mount joints. Now the full transceiver is working well (but yet to be put into 100mm optics) and the RX sensitivity is close to that with my K3PGP design RX. In the coming weeks I hope to get a transition piece to connect the transceiver "tube" to a 110mm drainpipe that houses the 100mm lens. I'll then assemble this onto a stable tripod with sighting scope and I'll be ready to look for QSOs.

http://www.earf.co.uk/optoposition.JPG

One thing that puzzled me was how having the detector diode and TX LED slightly off-centre would work. In my mind I thought that the light would not be properly focused onto the devices, so losing sensitivity. Then someone pointed out that by slightly aiming "off beam" by around 1 degree the light would fall exactly onto the position on the transceiver where the LED or PIN diode are mounted.

Finningley optical transceiver progress

In the last couple of days, armed with my wife's close-up reading glasses, a magnifying glass, tweezers and a fine tipped soldering iron, I have been doing the SMA build of G4HJW's "Finningley" optical transceiver kit, designed to be used with 100mm optics (drain pipe and Poundland lenses!).

The G4HJW designed optical transceiver

Bernie's instructions were first class with all the SMA parts for the receiver and the transmitter being organised sequentially with a clear layout diagram showing where each part has to be placed. It seems to have gone together very well with no snags, although I have still to add a few discrete parts including the LED and the PIN photodiode before testing can start. All being well, I should be able to start testing on Sunday as I am tied up with our church fete tomorrow.

G4HJW "Finningley" Optical Transceiver kit

The G4HJW optical transceiver kit

Bernie G4HJW is well known for his innovative work on microwaves and optical comms. Last year he designed a neat, part SMA, optical transceiver kit to build at the Finningley round table meeting. The transceiver is capable of very good results and several (around 70) have been built and used very successfully. I believe the best DX QSOs at 481THz have been over 60km using these in 100mm optics.

Exactly when I'll get my kit built I'm not sure but it will be good to have one of these available for optical line-of-sight tests in the autumn. Once assembled, I shall be looking for some 2-way optical QSOs beyond the 10km speech contact I achieved with my own kit last summer. In East Anglia, the issue is finding some hills to allow long line-of-sight paths.

Bernie is, I understand, considering putting together a further batch of these kits, which make a good introduction to nanowave communications. In addition to these electrical kits, all that is needed is a microphone, headset and some simple optics than can be built for a few pounds.

See http://www.earf.co.uk/nanotrx.htm for more details

7 mile optical daytime QSO by Bernie G4HJW and Jenny G0VQH

G4HJW and G0VQH enjoyed a successful 7 mile optical frequency QSO during daylight when in Scotland recently. Bernie also worked GS3PYE/P. There is a video of the QSO recorded by the good folks at Cam Hams. The QSO used the now famous Finningley optical transceiver designed by Bernie last year in 100mm (drain pipe!) optics. They were going to try an infra-red QSO too but as rain set in they abandoned the attempt.

Another earth-electrode station on 472kHz

If you spot G4HJW/1 on the WSPR database on 472kHz this is Bernie who is about 9km from me on his 30m baseline earth-electrode antenna. G4HJW is him on his Marconi by the way. Looking at his unique spots, he is getting reports from all over the place: not as good as his Marconi but reports out to over 900km isn't bad (GM, F, PA, G etc).

Next week, after the snow has gone, we hope to have a 2-way CW QSO on 472kHz using earth-electrode antennas at each end. That should be fun!

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.

Finningley Optical Transceiver (G4HJW)

Bernie G4HJW is well known for his innovative microwave designs as well as many other good projects in recent years. This year he has produced another winner for the Finningley Round Table in mid July:  a baseband optical transceiver kit designed with SMA components. For details see http://www.earf.co.uk/nanotrx.htm . I am not sure if Bernie is planning to make kits available more generally. Bernie has tested this design over a 65km line-of-sight path recently.

Further 481THz G4HJW reception "over the horizon"

G4HJW received on 481THz over an 8.63km non line-of-sight path

Bernie G4HJW was 20dB S/N in 0.67Hz bandwidth earlier this evening at my local test site 8.63km NLOS from his QTH "over the horizon". Bernie was using his Phlatlight beacon with 1.082kHz tone. The sky was clear and starlit, so this was clear air scattering not cloudbounce.  About 15 minutes after I first copied him it seemed to get more hazy and I was struggling to find his signal at all.  Best results appear to be with a clear sky and aiming at the horizon. 

On 3 attempts copying G4HJW's optical signal it has been (1) 30dB S/N, (2) no copy and (3) today 20dB S/N in 0.67Hz bandwidth over an 8.63km NLOS path. I am still using the BPW34 detector in 100mm optics.

A local 478THz (red light) beacon !

Map showing coverage of the 471 THz optical beacon GB3CAM

Guess what - I've just discovered that not only is there a decent level of optical comms activity in my area, but there is also an active 478THz beacon beaming (almost) in my direction from the Wyton site near Huntingdon, location of the GB3CAM beacons on 10GHz and 24GHz. The beacon is a narrow beamwidth (5 degrees wide) signal which is FSK keyed between 1 and 15kHz allowing both baseband and hetrodyne optical receivers to be used. The beacon was designed by Bernie G4HJW. The distance from the beacon to my local /P high spots in the beam would be around 30km, so this will be an ideal test for the optics and receiver, when built.