How, pray tell, did you calculate 6 db f/b on a VERTICAL? ... Did you
rotate it? Any WHY?
Don
N8DE
:)
Yup. I should have explained. The R7000 was mounted on the mast, about 3'
above
the yagi or lpda. I wanted to experiment with the interaction,
so I set it up with a friend, who had a kenwood ts 850 and
a program called "s meter", which will allow a rotational plot
of S meter output. He said go...I transmitted. Rotating the beam produced
pretty much the expected outcome. Rotating while driving the vertical
surprised me.
At first, I thought they were directly interacting. However, by
using rf chokes and separating the feedlines, I was able to get
the vertical's "pattern" down to about a 1dB variation. changing
to ONE feedline, and switching at the top of the tower reduced that
by another .5 dB. Disconnecting the beam and grounding the feedline
to the tower eliminated the vertical's "pattern" completely.
In later installations, I had a 40m beam and eliminated the vertical.
n2ea
jimjarvis@ieee.org
-----Original Message-----
From: Don Havlicek [mailto:n8de@thepoint.net]
Sent: Saturday, June 26, 2004 7:32 PM
To: jimjarvis@ieee.org
Cc: Towertalk
Subject: Re: [TowerTalk] beam antenna patterns; groundwave
How, pray tell, did you calculate 6 db f/b on a VERTICAL? ... Did you
rotate it? Any WHY?
Don
N8DE
Jim Jarvis wrote:
>
> Folks,
>
> While I agree with Tom, in theory, that all manner of localized
> effects can come into play, mapping pattern using groundwave at
> far-field has SOME value. I did it routinely in Vermont, with a
> station 5 miles away. We had hills and trees in between. What came
> back was quite close to claimed specification.
>
> To be sure, the groundwave pattern isn't the same as that at real arrival
> angles. But it allowed me to estimate f/b on both an lpda and a steppIR,
> and to do it against a co-located vertical antenna. The vertical was used
> as a frame of reference. The technique also allowed me to properly
> decouple
> the feedlines. When we first started, I had a 6dB f/b on my vertical!
> Adding common mode chokes and running the coax down separate tower legs
> tamed that beast.
>
>
> n2ea
> jimjarvis@ieee.org
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
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>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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