New Doublet and Balanced ATU in operation

Post date: Mar 05, 2013 11:57:22 AM

The nice spring weather is here and the ladders have been out!

The doublet is as long as I could manage at the moment which is 13 m (6.5 m each leg). I considered making it smaller and cut as a half wave on 20 m (5 m each leg) and I may do this in the future if anyone tells me it will be more efficient - I'm sure it won't as resonance is not a passport to efficiency!

The doublet is a sloper about 5 m high at one end and 2 m high at the other - I hope to even this out later in the year. It is aligned north-west to south-east giving best take off to the north-east and south-east.

The tuner is a VK5BR single coil balanced tuner which I threw together - it needs some reduction drives but I have a nice case for it to go into as soon as I find some nice vernier reduction drives.

That said it works a treat!! Tunes up on 15 m upwards even though the doublet is a little short for 15 m.

The adjustment of the capacitors is critical but I have it cracked. TIP: switch on the attenuator and CW filter and tune for maximum noise; I then tune at 5 Watts, 30 Watts and for smoke and have usually been spot on!

Talking of smoke the padders on the dual gang variable were far too weak and gave a lovely blue spark when transmitting. They were removed completely with no adverse affects.

Since using the doublet and tuner I have increased my QSO count 5 fold over my XRC X-80 vertical! A rough coverage map after a few days' use is shown below. As you can see the coverage seems to be worse towards the south-east but I need to do a little more weekend activity to see if I can get to the middle east, I also have small mountain a km behind me in that direction.

I will keep a few of these maps in the future just to see how the operation improves.

The next project is a 40 m dipole at a tangent to this so firing to South America and Asia for some hopeful DX and I can use that as a doublet for the higher bands and switch over to get the best signal out.