Saturday, August 20, 2016

100mW's of raw power!!

The other evening I was having a cup of tea and checking out my new QST that just arrived and found myself very interested in a piece written by Steve Ford in his column Eclectic Technology. The title caught my eye "When a signal is barely a WSPR" Steve looked at how the Raspberry Pi could be used for WSPR transmissions. Seeing I have the Raspberry Pi3 this sparked my interest. It was pointed out that all you need to turn your Pi into a WSPR transmitter is a board from TAPR called QRPi.  The board is offered at a very reasonable price of 29.00 U.S and it's set for 20m at 100mW. Before I got to excited about this little project  I wanted to see if using 100mW's would net me any results. I have seen other hams in the past net great results with far less than 100mW's and WSPR is known for it's great decode at very low power........BUT.......I do have a challenging setup here. On Friday late afternoon I gave WSPR a go on 20m at 100mW and was I impressed with the results. I was received by DK6UG for a distance of 39383 miles per watt and also ON7KO for a distance of 37285 miles per watt. I was amazed that my setup was able to produce those results! Now another question I wanted to consider is at 100mW how much of that actual power makes it to my antenna? To do this I referred to a coax calculator I punched in the type of coax (RG8X) the SWR (1.4:1) the length (30 feet)  the frequency (14) and finally the power (100mW) The calculated amount I was informed was 92mW of raw power! So this bumped my miles per watt to 42810 for DK6UG and 4053 for ON7KO! It's not timo look more into the TAPR project!!


Paul Stam PAØK said...

Hi Mike, great job, it's really amazing. Good luck with the project. Have a nice Sunday, 73 Paul PC4T

VE9KK said...

Good morning Paul, I was very pleased with the results and as for the project I will do some looking into things and maybe when the weather cools down it will be a nice thing to do.
73, Mike

PE4BAS, Bas said...

Wow, great result Mike. I think you have to go on with the project. I'm not that active at the moment as time is a issue. I'm currently TXing with my small W5OLF WSPR transmitter (30m) on 1W and the magnetic loop in my garage. Till now best distance was about 2000km. 73, Bas

VE9KK said...

Good evening Bas, I too was very happy with the results. This afternoon I was on again and my 100mW signal made it into Scotland. I for sure am going to move forward with the project. It will help pass time as the winter comes this way.
Have a great week
73, Mike