If you want a "plain language" explanation search CQ for the article titled,
"A Verbal Graphic Description of How Gain Antennas Work". It was back in the
70's but I've forgotten the specific month and year. I'll see if I can find
it. I should have a copy around here some where, but finding it is something
else. It was written by some guy with the call K8RI.
73
Roger Halstead (K8RI and ARRL 40 year Life Member)
N833R - World's oldest Debonair CD-2
www.rogerhalstead.com (Use return address from here)
> No one on the SteppIR yahoogroups forum has responded to my posting.
> Maybe some Towertalkians are interested and knowledgable?
>
> k7puc
> ----- Original Message -----
> From: Al Williams
> To: SteppIR@yahoogroups.com
> Sent: Thursday, July 27, 2006 1:10 PM
> Subject: Re: [SteppIR] 3El height
>
>
> Jerry, k3bz, sets forth an interesting concept that tuning the SteppIR
> elements may somehow change the vertical angle of maximum radiation for
> Yagi type arrays.
>
> For some time I have been trying to understand why/how Yagi antennas
> provide directional gain. In going through about 20 antenna books written
> for the ham community, only one offers what appears to be a technical
> explanation. This book is Lawson's "Yagi Antenna Design", but its
> explanation uses too much trigonometric formulas for me to wade into. All
> other books limit their explanation to two factors: 1. that the
> magnetic field caused by current in a antenna causes an induced current
> into adjacent wire/elements which then radiates its own electromagnetic
> wave. 2. The electromagnetic wave from this adjacent element adds to the
> electromagnetic wave from the driven element
> which results in a composite wave strength at distant receptions. The
> composite wave strength may be greater or less than that from the driven
> element alone depending on the phase difference between waves at the
> receiving site.
>
> The phase difference is caused by three factors: 1. The distance/time to
> the receiving site from the driven and the induced elements signal.
> 2. The phase difference in the induced element causes am 180 degree lag of
> induction plus a phase shift if the adjacent wire is not resonant.
> This non resonant adjacent wire appears to answer why a reflector is
> longer and a director is shorter than the driven element.
>
> 3. The third factor is the phase shift caused by a distance/time of the
> parts of the wave being (reflected/reradiated?) from the source on its
> journey to receiving site. Note that I haven't mentioned the angle of
> reflection here!
>
> Now, I think that Jerry is suggesting that this third factor can be
> compensated for by adjusting SteppIR's element lengths.
>
> Well, why not??????
>
> k7puc
>
> BTW Why does a dipole have a directional pattern?
>
> ----- Original Message -----
> From: Bill Tarkington
> To: SteppIR@yahoogroups.com
> Sent: Thursday, July 27, 2006 11:05 AM
> Subject: Re: [SteppIR] 3El height
>
> FWIW, I use my 3L at forty feet due to lot size limits, and it works on 20
> quite well. Better than I had ever hoped!
> ----- Original Message -----
> From: Jerry Keller
> To: SteppIR@yahoogroups.com
> Sent: Thursday, July 27, 2006 11:33 AM
> Subject: Re: [SteppIR] 3El height
>
> With respect, I have to disagree with Mike on this. The SteppIR 3L works
> great on 20M at 40 feet. In fact, much of the design and testing was done
> at
> about that height. The great thing is that, although 40 feet might not
> always be the best height for a fixed monobander, much of that is overcome
> overcome because the SteppIR is tunable. I bet half the 3L users out there
> are closer to 40 feet than to 55, and some are much lower and still get
> excellent performance. I know I do.
> 73, Jerry K3BZ
> ----- Original Message -----
> From: "Mike K6BR" <noddie@comcast.net>
> To: <SteppIR@yahoogroups.com>
> Sent: Thursday, July 27, 2006 10:46 AM
> Subject: RE: [SteppIR] 3El height
>
> I would say 55 feet is minimum for 20 meters; if you don't care about 20
> meters have the beam lower.
>
> Mike
>
> I have started stacking the tower. What height is ideal for the 3 El
> beam. I'm at 40 feet now shoud I go another 10 feet or stop now.
>
> Ron
>
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