One Laptop Per Child (OLPC)

Good to see that Uruguay has become the first country to provide a laptop for every child attending state primary school according to a report on the BBC News website today as part of the OLPC Initiative.  Over the last 2 years 362,000 pupils and 18,000 teachers have been involved in the scheme, which aims to provide low cost, but high specification, laptops to school children across the world.

500kHz paths

The map here shows the distances spanned on 500kHz WSPR with my QRPp station. I'm now beginning to believe that further will be possible, especially with some skywave propagation. 210kms DX already means I've a chance of being heard in GW, ON, and PA if stations are listening in these countries and uploading spots to the WSPR database.

My new 500kHz DX record - 210kms

Just been reported by G3YMC in Bracknell, which is 120kms away and my 6th station to report me and my best DX to date. Then I got a report from G0KTN at 210kms away!! It's gradually getting better.

Incidentally, this is the transverter at the moment very ugly style. Will add the RX part soon so I can use CW.

Dave's G0YMC's report:

153000 15 10 2.6 -62 0 G4JNT IO90 23
153000 8 -20 5.2 8 1 G3XBM JO02 0

Wow, only 30dB down on G4JNT! Well done Roger.

(sorry cannot upload as I am copying with WSJT7 which doesn't support
the internet upload - but has an auto soundcard calibrator).

73 Dave G3YMC
IO91PJ

5W (from the PA) on 500kHz

With the arrival of some IRF510 FETs I've built a small PA to go on the end of my WSPR beacon transverter. The output (from the PA) is now 5W, so my ERP should be up by around 10dB to around 50-60uW. Already I have been spotted by G7NKS some 10dB stronger than ever before - most encouraging!

The first transistor - read Shockley's lab notes

Take a look at William Shockley's hand written lab notes at Bell Labs when he created the first point contact transistor back in December 1947. Little did he know then what this would lead to in the next 60 years. Amazingly the patent wasn't filed until 1951. Who actually invented the first transistor is debated and was the result of separate discoveries and hard work by many. This is often the case in science.

500kHz WSPR - last time before improving the station

This evening and overnight I am running my 500kHz WSPR beacon for the last time in its unmodified state before beginning to make improvements to the antenna and PA. I am still hopeful that I'll get another one or two new stations spotting my signal. Once the ERP starts to be increased by up to 20dB my "sphere of influence" on 500kHz should increase.

Do listen on 500kHz WSPR and upload any spots you get.

POSTSCRIPT: I did actually fire the "old" setup again last night (Friday evening) for a few hours but was only reported by G7NKS. I'm now thinking of practical and relatively unobtrusive ways of making the signal a bit more potent on 500kHz without the garden looking like Droitwich or GBR Rugby.

A new station hears my 500kHz WSPR QRPp

This evening I received reports from G0BPU in Ipswich on 500kHz WSPR, This is now the 5th station to have heard my 6uW ERP signal. I am still hopeful that I will beat the 100kms barrier before I start the station improvements. Other reports today came from M0BMU and G7NKS. My best DX remains at 69kms.

500kHz WSPR restarted - please listen

In the coming weeks I shall be improving my ERP, but to get a baseline I've just restarted my 500kHz WSPR beacon which is believed to have an ERP of around 6uW (microwatts). Since starting it up I've already received reports from M0BMU at 69kms away with S/N levels ranging from -24 to -29dB. These are the levels I was getting last month, so all is still working (see picture of the WSPR database).

If you are able to listen on 500kHz WSPR set you receiver to 502.4kHz in USB mode and click "upload spots" on the WSPR screen so that your SWL reports will be added to the database on the internet automatically.

It really would be good if more people listened on 500kHz WSPR even if they can't TX. WSPR is very easy to use especially on RX and the WSPR software can run in the background whilst you get on with something else. The WSPR software can be downloaded from http://physics.princeton.edu/pulsar/K1JT/WSPR112.EXE

All reports really would be most welcome.

161kms voice powered QSO by AA1TJ

Just got an email from Mike Rainey AA1TJ describing his TX powered only by his voice. He achieved a distance of 161kms with a germanium transistor oscillator putting out a few mW of power. The power for this was generated by rectifying the audio signal from the loudspeaker used as a microphone. In the end Mike resorted to a sort of MCW mode shouting CW into the LS but W1VZR copied this and made a recording. Mike is also looking at a receiver using "RF harvesting" to allow a receiver that requires no DC power source other than that derived from off-air RF.

Mike's amateur radio pages are at http://mjrainey.googlepages.com/radio

Free power QRPp transceiver or beacon?

The idea of powering a low power receiver, or even a transceiver or QRPp beacon, from free, otherwise wasted, RF energy that is all around us appeals to me. A few people have been toying with this idea and there are even some commercial ICs likely to appear which "harvest" energy from stray RF and even vibrations. The circuit shown here is from the excellent site by KE3IJ (R.Andersen) and shows how to use 50 or 60Hz mains "fog" and stray RF to power a simple receiver. See http://www.tricountyi.net/~randerse/nopower.htm .

See also Ben Tongue's crystal set pages for a circuit using a supercap to store harvested energy which is then used to power a micropower op-amp.

A "harvester" QRPp transceiver or beacon which derives its energy from stray RF, storing this is in a supercap and allowing brief periods of transmission at very low power is worth developing I think. I have not seen such "harvesting" circuits used to power a transceiver or beacon before but for a uW level beacon this should be feasible.