Topband: T Top Verticals and yagis

[HA3LN]

Hi All,

What if I use 2x flat tops instead of one spaced evenly?
If I recall correctly this config has 60% of length of the single one.

Does this solve the degradation effect?

73!
Csaba  HA3LN / HG3N



On 2020-02-28 5:23, donovanf at starpower.net wrote:
> Hi Ed,
> 
> 
> Your conclusions based on your modelling are completely consistent
> with my practical experience and modelling.
> 
> 
> The most likely degradation is a T-top between 60 and 75 feet long
> degrading the front-to-back ratio, pattern and gain of a 40 meter
> Yagi when its main beam points into a T-top that's roughly parallel
> to the 40 meter Yagi elements.
> 
> 
> Only the 40 meter Yagi is affected, especially if the Yagi is within
> about 400 feet of a 160 meter T-vertical with a 60-75 foot T-top.
> The 160M T-vertical is not affected.
> 
> 
> How to avoid degradation of a 40 meter Yagi?
> - avoid T-tops between 50 and 75 feet long, or
> - use an inverted-L rather then a T-vertical
> 
> 
> All of the above is based on actual degradation of my 3 element 40M
> Yagi by a 160M T-vertical 40 years ago. Changing the T-vertical to an
> inverted-L returned the 40M Yagi to its prior excellent performance
> 
> 
> tks
> 
> 
> 73
> Frank
> W3LPL
> 
> ----- Original Message -----
> 
> From: "Ed Sawyer" <sawyered at earthlink.net>
> To: topband at contesting.com
> Sent: Friday, February 28, 2020 2:47:34 AM
> Subject: Topband: T Top Verticals and yagis
> 
> Frank had brought up the interaction of certain T top loading wires and the
> possible interaction with yagis. I played around with modelling on this and
> found that just as Frank said, there is interaction of T top wires and
> yagis. One thing I found was that if the wire is in the front pattern of
> the yagi it is much more influenced if the wire is the front 1/3 portion
> rather than the sides and back of the yagi. I didn't find meaningful
> distortion in the back area 200 ft away but closer than that and approaching
> the front, and there was definite distortion.
> 
> 
> 
> Interesting topic Frank.
> 
> 
> 
> Ed N1UR
> 
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