Re: Topband: 90 ft or 120 ft vert fer TB

[Rick Karlquist]

vk...@vk3pa.com wrote:
> Hi all,
>   after loosing my 90ft top loaded vert (wind storm 120kph +++) fer
> TB, I find I have enough meteral to go to a max of 120foot vertical (
> 4 lengths @ 30 ft)
> Q is, if I base load will this be much better than my 90 ft top loaded
> vertical was?
>   (108 dxcc wked/12 months)

The advantage of top loading for the 90 footer will almost
make up for the height advantage of the 120 footer.  The
structural degree of difficulty is much greater for 120
feet than 90 feet, so it would be hard to justify 120 feet.
If you have a good enough ground, there is no advantage
to the additional height (except greater BW).

Rick N6RK

___
UR RST IS ... ... ..9 QSB QSB - hw? BK

Re: Topband: 90 ft or 120 ft vert fer TB

[Herb Schoenbohm]

On 2/9/2012 7:01 PM, vk...@vk3pa.com wrote:
> Hi all,
>after loosing my 90ft top loaded vert (wind storm 120kph +++) fer
> TB, I find I have enough meteral to go to a max of 120foot vertical (
> 4 lengths @ 30 ft)
> Q is, if I base load will this be much better than my 90 ft top loaded
> vertical was?
>(108 dxcc wked/12 months)
>
> or Should I still go fer a 90ft top loaded 4 sq array?
> With a signal vert I run a triangle phased array HI-Z
> ___
>
A 120 vs. a 90 foot top loaded is a matter of choice since the RF 
doesn't really care since the 90 foot top loaded can look exactly like a 
120 foot unipole.  The 90 footer, depending on the amount of top loading 
most the current maximum  up the tower near the top.  The current 
maximum never appears at the tip of a 120 footer.  So the answer is to 
do what ever is easier as it is the top loading that makes all the 
difference, assuming the radial field is the same.  Problem with a 120 
foot tower is that when you start putting beams on top the feeding may 
become more difficult as the tower at RF approaches 1/2 wave electrical.


Herb Schoenbohm, KV4FZ
___
UR RST IS ... ... ..9 QSB QSB - hw? BK