481THz over the horizon test: no success tonight

Weather this evening was not suitable for the tests, although I did try. I set up the QRSS3 beacon pointing out of my bedroom window using the local windmill as the aiming point. This is on the top of our small hill which rises about 15m. I then drove to a spot 3.6km away over the hill to look for the signal with my sensitive RX and 100mm optics using Spectran to display the trace. Unfortunately this time the slight drizzle and murk was just too bad and no signal was copied, although I've had good results in the past at a very similar spot.

In daylight I need to recheck my beam alignment at the RX location as it was sufficiently murky to not see the local landmarks used to help aim the RX last time. Despite panning across 45 degrees of aim nothing at all was copied of my signal. I shall repeat the test in better optical conditions.

For those interested, the 1W 10mm diodes are available from http://www.ebay.co.uk/itm/350347623711.  You get 10 pieces for £9.26 with free postage and they are very BRIGHT.

481THz optical tests over the horizon tonight

This evening I am doing my first "over-the-horizon" optical test this year. The main aim is to check performance with the new receiver and to see how I get on using the iPod Touch 4g running SpectrumView software as the way of seeing the QRSS3 signal. I shall also be taking the laptop running Argo or Spectran.

Latest receiver that seems more sensitive than my older RX

The receiver circuit is the one in Practical Wireless this month by Stuart Wisher G8CYW. This is simple but works well in darkness. I've added an interface to the iPod Touch 4g (a capacitor and a resistor needed to enable the external mic input) and changed the coupling caps and op-amp gain. Using just MPF102 and 2N3904 devices the results look good. The low noise op-amp may be overkill unless one uses super low noise FET and transistor stages too.

After the tests I'll post results in the blog.

40m WSPR with 50mW - best DX spot 6505km

Reports received with 50mW on 40m

Overnight I've been WSPRing with 50mW output on 40m using the Par 10/20/40 end-fed antenna down the garden.  The FT817 set to 500mW directly feeds a Telonic 10dB rotary attenuator set to 10dB attenuation, so no chance of radiation from a coax cable. The antenna is only about 15m long and just 5m average height above the ground. Results (see above) have been very pleasing with best DX report from the USA - K9AN at 6505km.

Bug keys

Kent twin paddle key

Although not a frequent or very good CW operator, I do like to try QRP CW from time to time, usually with a straight key I've had for over 40 years. With rubber stamp QSOs on HF I can usually manage OK. The problem comes when people ragchew and I lose concentration!

Some years ago I bought a beautifully made Kent paddle key but I've hardly ever used it because I kept making mistakes. So, today I dug it out and decided to persevere with it on 40m CW. I managed a nice (unexpected) 2-way QRP QSO with Rick DK4QK who, despite my sending, managed to copy everything. Later I worked DM0E on 2-way QRP as well, using the bug. Like all things, good CW comes with practice and use. Using a paddle key should allow me to send better and faster CW with a little bit more practice on my part.

So, if you hear me calling CQ on 40, 20 or 10m in the coming days on CW, and there are plenty of mistakes and extra dots, then you'll know who it is.

20m WSPR

As the weather is totally miserable I decided to sit by the fire today instead of doing any amateur radio building. In the comfort of the lounge I am watching the spots being sent and received with 2W to the Par 10/20/40 end-fed antenna on 20m WSPR. 20m is not a band I use much, preferring 10m, although conditions on 10m have nothing like matched the conditions close to past sunspot maxima.

Some decent range spots (TX and RX) despite lackluster conditions on 20m

Exchange rate changes and ham rigs

In recent weeks the pound sterling has declined quite a bit against the US dollar and the euro. Against the dollar it has fallen from around 1.62 dollars to the pound to around 1.51 to the pound. This makes purchases of rigs like the KX3 even more expensive here in the UK.

On the other hand, the yen has weakened from 125 to the pound to around 142 to the pound.  Expect some discounting of Japanese rigs in the UK incoming months.  The latest yen exchange rate suggests a new FT817ND should be less than £500 again soon.

Which major dealer will be really public spirited and pass on their savings to us the amateur radio public?  Martin Lynch or Waters and Stanton?

A PSK31 QSO

Well, the little grandchildren have gone back home to mum and dad so the house is very quiet (and tidy!) again. This afternoon I decided to do a bit of QRP on 20m as a change. First a nice 2-way QRP QSO with Emi IZ4RDX who was running 5W (me 2.5W) and then a PSK31 QSO with Luis EA3UV. Neither contacts were great DX, but fun.  For the PSK31 QSO I decided NOT to use those pre-prepared messages and instead just keyed in what I wanted to say as the QSO went along. It felt like a real QSO, which was nice.

Tomorrow I hope to get back to the optical beacon work, but after 4 days of (lovely) little grandchildren this afternoon I just needed to "chill" as they say.  The plan is to build a beacon TX that will allow a range of subcarriers and also continuous subcarrier transmission as well as CW and QRSS beacon messages. I hope to get out "over the horizon" looking for the signal later in the week. Watch this space - literally if you are nearby, HI.

PSK31 mode

Julian G4ILO mentions his enjoyment of PSK31 on HF on his blog today.  Although I've had a fair few QSOs and some good DX with this mode over the years, I'm not a great fan of it.

Although Julian rightly says it is a very good mode that well complements CW and SSB, and it is certainly true that the PSK31 part of the bands are often busy when CW and SSB signals are absent, to me QSOs feel too formalised with exchanges that follow fairly standard formulae. Too often it feels like a PC talking to a PC. Maybe I should try next time to avoid using these pre-programmed messages and go for a normal free-form keyboard "chat" instead.

It's a while since I've tried PSK31 on HF. Maybe next week when the grandchildren go home I'll give it another go.

The ARRL reports that Varicode, as used in PSK31, has now been officially recognised by the ITU. See http://www.arrl.org/news/amateur-created-varicode-adopted-as-itu-recommendation .

More VLF activity from Germany

DJ8WX has been experimenting with a new GPS locked frequency source and is trying to put a signal out on 8.9700000kHz.  The signal has been received strongly by several stations including Paul Nicholson in Todmorden and at PA1SDB. This is the signal at PA1SDB over the last few days. Note the timescale on Peter's grabber covers several DAYS. Such is the world of amateur VLF!

Signal from DJ8WX now on 8.970000kHz (was 8.970022kHz)

Nanowave over the horizon tests - nearly ready

Original optical beacon

Just about ready now to restart my optical non line-of-sight tests again using my 481THz CW/QRSS beacon and a choice of 2 sensitive receivers. I'd intended to go out this evening but (a) the XYL needed the car to go to her choir and (b) the fog has descended!

Optical beacon capable of continuous subcarrier (choice of freqs) or QRSS/CW

SpectrumView in action - it's brilliant

The beacon design needs to change somewhat: currently I can TX either QRSS3, QRSS30 or CW at around 830Hz subcarrier, using the IRF640 fed directly from my K1EL keyer IC. However, I cannot actually send just a 830Hz tone continuously. This would actually be very useful when aligning TX and RX over a non-optical path e.g over a hill. So, when the grandchildren go home on Sunday I'll make a modified version of the beacon keyer so that I can choose a number of subcarrier frequencies, including some lower than 830Hz (detector sensitivity is greater at lower audio frequencies) and also add the option of a continuous subcarrier signal. This will involve adding a 4060 based oscillator and divider to be keyed by the K1EL keyer IC. So, it may be next Tuesday or Wednesday before I actually start testing again.

I also want to optimise the use of the iPod Touch 4g as a handheld audio spectrum analyser. I have used it for this sort of test before using an excellent package available free called SpectrumView (see screenshot) available from Oxford Wave Research. With a laptop PC, running Spectran, the problem is the brightness of the screen which emits an interfering optical signal. With a tiny iPod Touch it is much less bright and can be held in the hand. Unfortunately the bandwidth can't be screwed down as narrow as with Spectran on the PC, so there will be S/N limitations. One test will be to see how far away I can detect my beacon (about 0.5W into the LED) over the horizon using just the optical receiver and the iPod Touch.

The beauty of 481THz (red light) work is the kit is simple: everything that matters is at audio frequencies and can be built and tested with the simplest of test gear.