Another new country on 500kHz WSPR

My 500kHz WSPR beacon has now been heard in a fourth country: a -26dB S/N report from F5WK who is in the Paris area, a distance of 436kms away to the south. The beacon has now been reported by 11 different stations in four countries so far.

Lambda diode circuits

Mike Rainey AA1TJ has some good tunnel diode ideas on his pages but these devices are hard to find these days. Instead one can create a negative resistance device called a Lambda diode with a couple of FETs or an FET and a transistor. See for example the pages of Ramon Vargas Patron at http://www.zen22142.zen.co.uk/Theory/neg_resistance/negres.htm where he has examples of oscillators and regenerative receivers using Lambda diodes.

500kHz WSPR - a summary so far

So far, spots have now been received from 10 unique reporters (9 via the WSPR database + G3YMC's report using WSJT7 not shown here) in 3 countries and 7 grid squares.

If I could summarise what this tells me it is:

(a) WSPR works very well at 500kHz allowing weak QRPp signals to be detected.
(b) Very low power (ERP <0.3mW) and electrically tiny antennas do work on 500kHz if weak signal modes are used.
(c) 136kHz is worth a go next, even with the poor antenna and very low ERP.

A map to end a fantastic day on 500kHz QRPp

This is the map that says it all: DX that even yesterday I would not have believed possible with a true QRPp microstation on 500kHz WSPR. I go to bed very happy, leaving the beacon running overnight in case any others manage to detect my signals.

K1JT, Joe Taylor, thank you for bringing us this wonderful software package.

What next - 136kHz WSPR?

Having now almost achieved more than I could ever have expected on 500kHz WSPR with uWs ERP, I'm wondering if I should give 136kHz a try with the same antenna and transverter. If I could maintain the same antenna current (20mA measured) my ERP would be around 3-5uW on 136kHz. I'm wondering how far that might get. Almost certainly not too far, but probably enough to be detected by some of the nearer stations

Even greater DX on 500kHz QRPp WSPR - 896kms!

This is getting unbelievable now with such low power and a simple antenna: having just got a report from OR7T I've just now got one at -26dB S/N from GM4SLV in the Shetland Is all of 896kms away! This has been one of the best days ever in my ham radio life.

International DX on 500kHz WSPR

Just received my first 500kHz report from outside England at -26dB S/N from OR7T in JO20ix which is 337kms away.

Using the formula in the RSGB LF Handbook I just calculated my ERP on 500kHz assuming an effective antenna height of 6m (probably less than this in reality) and a measured antenna current of just 20mA. It works out at 315uW ERP. Based on earlier measurements by M0BMU it should now be around 60uW. I suspect he is nearer than the theory suggests. Anyway, still a long way below 1mW ERP even but getting great results with WSPR.

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