Topband: Shunt-fed tower vs. T-vertical

[Herb Schoenbohm]

Rudy Bakalov wrote:
> I have never model an antenna before and thus have no idea what the electrical length of the tower is. Furthermore, I plan on adding 2 more tribanders next year, at 68' and 30' so the loading will change. Finally, all the books I have read on shunt-feeding a tower have created an impression that doing so is not as trivial and certainly not plug-and-play.  Thus, I am considering the much simpler and more predictable T-vertical.
>
> Remember there will most likely be some interaction between the "T" and the grounded tower distorting the pattern, if one end of the T is supported by your tower.  I have found the easist way to tame a shunt fed tower is to feed it with a three or four wire cage rather than a single wire shunt and the complexities of feedlines and rotor cables being part of the mix.  The cage does the radiation essentially decoupling a lot of what is run inside it.  Chokes and grounding at the base is still imortant however.
>   


Herb Schoenbohm, KV4FZ