Monday, 16 September 2013

QRP and the Attic Dipole

I have been lucky enough to be blessed with enough space to play with a few antennas and mini beams here at my current QTH, I have also been blessed with a tolerant wife; she has put up with lots of aluminium and wire all over the garden not to mention the small mast mounted on the side of my house. My current antennas on the main station on HF are the MQ-1 mini beam for 20,15&10m and a butternut HF9-V vertical antenna covering 160m through to 6m. 

I really wanted to put a second radio next to my bed for the evenings when insomnia grips. This means that with a small set of headphones I can listen to CW on the bands to practice my copying skills. The big issue was what antenna to use. I made up a few different experimental antennas and had some success with a wire and a small QRP homebrew 9:1 transforming unun. 

The thought came to me to try and fit a small set of nested dipoles for 40, 20,15&10m fed with RG-174 mini coax. It took me about an hour to get a dipole squeezed into the attic space and then another two hours of fine tuning, rafter traversing and ladder climbing to make it all work. There was nothing complicated and it was made with very simple engineering and junk box bits and scraps of wire. The beauty of attic antennas is there is no need for weatherproofing at all.

The nested dipole attic antenna I now use is a 40m dipole bent into a square and a 20m and 10m wire added below them. A rough drawing is shown below. I make use of the 40m dipole on 15m with some good results. So far the best DX is KP4 on 15m at just 5w SSB. Do not underestimate the performance of simple wire antennas, a wire dipole and QRP can perform very well indeed. 

The real test for me now is to get confident enough with my CW to progress to some contacts using a more efficient mode. I am confident that once I make that jump I will be spending more time at low power and may even consider taking down the mini beam and masses of metal from the mast.

Below you can see a rough plan of how I have had to bend the wires to fit them in, the good news is it works very well and my wife hasn't noticed yet that I have an extra three antennas.



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