zaterdag 8 augustus 2015

new 80m full size vertical

Finally !  One year after the installation of the basic structure, fantastic home-made work by Franki on5zo, the 80m has been constructed.

I'll never dare to post in detail why we needed a normal car, a small tractor, a 4x4 Jeep and a big tractor to place a piece of iron in the garden, but it has something to do with bad ground quality and a bad judgement of the terrain owner...

Back to the antenna.

In fact it exists of 3 parts : the 9,8m recuperated KT34XA boom, a spiderbeam fiber mast and some pieces to keep the wire (I use a wire for the radiation part in stead of the alu of the boom) away from metallic structures.

One day of testing learned me a lot of things : first with 8 radials laying on the ground I could cut the antenna to a resonant frequency on 3.550 Mhz with an impedance of 53 Ohm.

Second test was to put 8 the radials higher (between 1m and 3m above the ground).  A expected, the resistance came down to 36,6 Ohm, but the resonance point went up to 3795 Khz.  Perfect for SSB DX, but not really foreseen.  This is i.m.o. due to the extra capacitive loading of the hanging radials.

Third test : everthing again on the ground, but 16 radials in stead of 8.  This time resistance showed 46 Ohm (as predicted in ON4UN's low band dxing book) and the resonance point went down to 3524 Khz.

I kept the config like that.

In the middle of the night I went up to test the antenna.
80m band was completely closed, I was the only station. 

After a few minutes of CQing, I looked up were my signal reports appeared.
I was heard in PJ3, 9K and had a good signal in VE3.  Best signals came from DL, F en SM, but it was only around 23h30 UTC.

Anyway; this looks good for the future.
For the first time I could use 1,3KW power in stead of the normal 800W delivered by the Acom1000.
Not one single Watt of power return.

Next step : go to at least 32 radials and maybe foresee 60 radials on ground.

QRM was heavy, so I need to continue with the receiving part of the game.  
A first good test seems the Worked all Asian contest in September on Friday night and Sunday evening (because of the SSB fieldday in the same mode/band on Saturday/Sunday).

21m is high, very high, even in a big garden.  I used 2x3 ropes to protect the fiber against wind.

The testing setup with an 2KW unun and Wago clamps to keep radials together.