Topband: my "Topbandstory"

[karvkari karvkari]

Hi all reflector users

I was asking earlier this summer lot of questions how to feed and how to tune/load 2 phasing verticals for top band. I received many mails  and  thanks all of you who help me .

"Shortly" I ended up following set up. Originally I use 2 Titanex HD160. As known these verticals have very flexible top section even they dont require any guying. So traditional capacitive top loading with wire would require mechanical shortening of flexible top part and additionally guying of lower part.

Finaly I decedid to go for top loading with inductance. I cutted element between second and third top section (at level 22.5 m) and added piece  fiber class for isolation. Original lengt of vertical was 26.6 m (+/- some cm), I extended top section by thin welding steel wire 1m + similar alumium 0,7 m (diameter of both some 1,5..2mm) Total length was a bit over 28 m. 

Then I calculated size of coils according ON4UN 4th edition formulas and ended up of 125 mikroH.

Coils are air wound from MFj, diameter 2,5 inch, some 100 turns wire size some 14. I tried to keep coil weigth low just to save mechanical load of vertical top part.  To get the both antennas to be on resonance required several liftings up and down to remome extra coil wire.
Before tuning I painted coils by similar laquer which we use in ABB electric machines windings.

Finaly both antennas were resonating at 1.830. I played a bit with number of ground radials to get both elements  having  same impedance. AA230 shows now R 40 and X 0, during summer we had very hot and dry period and R was rising  up to 44 ohms. Phasing is made by Comtek hybrid coupler.  Front to back is some 18 db.  Phasing distance between verticals is 39 m.

For winter I will add more radials.

During summer I have vorked smany dx and results are promising. Also non guyed vertical with extra coil and length managed to withstand exream high thunderstorm. Many trees were falling down durin storm.

Verticals are still up !
Hope  to work you durind next season.
73 ! Kari OH5LF