Thursday, May 15, 2014

Ultimate QRSS U3 Transmitter

Ultimate QRSS U3 kit is developed by Hans Summer.  It can transmit multi mode like QRSS, FSKCW, DFCW, Hell, DX Hell, Slow Hell, FSK, CW, CW ID, WSPR, WSPR-15, TX and customisable patterns.

Thanks to Hans for developing wonderful kit, its very reasonably priced and I would recommend to buy rather than building one.

I decided to build myself as I had most of the parts in my junk box, left over components from earlier rf projects. I had already built W3PM WSPR project, but wanted to make a multi mode this time.

I primarily transmit WSPR on dipole antenna with just 2 watts of rf output. I use MR-87 GPS unit with external antenna, with this setup I was able to reach 16k km.

You can see latest WSPR reports Here.

Please note that for this project I had to write code for PIC12F675 for controlling GPS MR-87. By default this particular GPS delivers all NMEA sentences which exceeds its 4800 baud rate ie RS232 bandwidth, resulting in erroneous output data. This is due to locked baud rate which cannot be changed due to firmware restriction. 

Therefore it required additional MTK commands to be given by 12f675 to GPS unit just to deliver $RMC sentence. This is done at every power cycle, without this arrangement U3 would not transmit on correct UTC time, within error margin of 1 second.   It has been working flawlessly, it wouldn't have looked wise to invest in another GPS unit. This problem was because of my GPS unit and nothing to do with U3.

Some photographs of my ugly construction.