Detuning the Tower

My vertical always gave me a solid performance. It is a stand free triangular tower made by Height Towers. The structure is modular in 8ft sections; the initial configuration had 9 sections (72 ft, 22m). On the top I had a 15 ft mast (4,5m) and a 50 ft boom yagi for 6m and a 36ft boon yagi for 2. My plan was to work VHF DX from my new QTH in Florida.

 

The radial system has 64 short radials, running from 50ft (15m) to 120 ft (40m)

 

 

 

South Florida is on top of an underground river called Everglades, yes if you dig 3 to 6 ft you get coral rocks, The coral rocks have holes like a big sponge filled with sand. If you remove the sand you get water, so what I did was  add a 6 ft each end of each radial to reach h the water level. The water is not salt water but it has a lot of metal ions, I still don’t know if this helped or not but was clear since the first day my vertical performance was very good. I fed the tower form inside, using a 3” pipe isolated in the bottom and connected with the tower at 24 ft (8m). The Band Width was only 30 KHz between 1:1,5

 

The writing is in Portuguese on this old picture. The 3” pipe inside the tower is was the gamma match; the series capacitor was 375pf and the parallel 1400pf.

It was so easy to work DX with 100 w that I start getting motivated again on Top Band. In my first US contest I worked all 50 states plus Alaska Hawaii and Puerto Rico.

With a narrow BX my vertical was quiet, may be because all grounded and fed from inside it was a good RX antenna for the winter. Well it was the only one I had; well my quest for a good RX antenna was just starting.

 

I first did a EWE and the results was very good, what an improvement from my vertical. I was definitely hooked again on Tob Band as my main activity.

I removed the antennas during the hurricane season, and I acquired some new sections to raise the tower to 85 ft, that when I figured out the 18”section connected with an old tower I bought few years ago, the results was a full size ¼ wave vertical with 118 ft (36m).

 

 

 

The vertical full size speaks for it self, I can work anything I heard, and this was exactly the issue. What about the stations I could hear? Well, I improved one thing but my EWE just stop working, kaput, ,, gone ,,,no more,,,

 

The reception with my EWE becomes equal to the vertical using 24db attenuator yes equally poor in all directions. It was a while until I figure out what happened. Reading a NCJ article about detuning the tower I figured you what was going on.

 

My tower was re-radiating noise and interacting with the EWE, I did several simulations using EZNEC and it was clear the distortion on the EWE pattern. Almost at the same time I got the new edition of ON4UN with new Small RX array of verticals and I started a project to detune the tower and build a small 4 square.

 

More Coming Soon!!