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HF launch angles, NCJ

Subject: HF launch angles, NCJ
From: AA5BANANA@aol.com (AA5BANANA@aol.com)
Date: Thu Aug 17 23:37:45 1995
For those of you who are interested in studying more about the effects
of terrain but can't get ahold of a copy of QEX, there's help on 
the way:

  The Sep/Oct NCJ has N6ND's review of Brian's new "Terrain Analyzer"
  along with examples and some general info about antenna/terrain

  Dean, N6BV, has revised/condensed his QEX article for us and it 
  should appear in the Nov/Dec NCJ.

Also in the Sep/Oct issue, unless there are some unanticipated 
last-minute cuts:

 *Review of the ICOM 775DSP
 *Phone NAQP results
 *CAC report (contest-free zones on 20 meters?!)
 *Collegiate Sweepstakes results
 *"Reflections" on the 2005 CQWW (a prophesy?)
 *ARRL DX Phone, KP2/KE2VB
 + the usual great columns, letters, ...

  -Bruce AA5B

>From Frank Donovan <donovanf@sgate.com>  Fri Aug 18 03:40:43 1995
From: Frank Donovan <donovanf@sgate.com> (Frank Donovan)
Subject: Phased Beverages! (was: EVE vs Beverage?
Message-ID: <Pine.OSF.3.91.950817221901.25930C-100000@jekyll.sgate.com>

I'm not sure there is an particular "optimal" height...
>From what I've read, very low Beverages (one meter or less) have 
excellent patterns (sidelobes and front-to-back) but very poor efficiency.
If very low Beverages are practical at your QTH, efficiency can be 
significantly improved by using a multi-wire Beverage rather than a 
single wire Beverage.  In this case I'm not referring to 1/2 wave-spaced phased 
Beverages, but to several close spaced Beverages (typically three).  You 
simple space the three Beverages side-by side, spaced from each other by a
distance equal to twice their height.  Ground losses of the three wire Beverage 
configuration are about 3 to 4 dB less than a single wire Beverage.  
Simple join the three wires at each end by sloping the wires toward the 
common feed point at one end and towards the termination at the other end.

Sidelobes and front-to-back should be acceptible on 160M at Beverage 
heights of 3 to 5 meters.  Heights above 2 to 3 meters are probably 
undesirable on 80M and two meters is probably a little too high on 40M for 
good sidelobe and f/b!
In my case, its very inconvenient and perhaps a bit dangerous to place my 
Beverages below head-height (for humans and animals - we have lots of deer 
who get tangled up in my Beverages every year)!   So I place my Beverages at 
about 2 meters height, with the last 16 meters at each end sloped down to 
ground leve at the feed and termination ends.


On Thu, 17 Aug 1995, Jerry Sidorov wrote:

> Dear Frank,
> could you tell me how high would be optimal Beverages for
> 160? 80? 40?
> --- 
>         73,  Jerry  UA9AR.
> Mail: Jerry Sidorov, P/O Box 9411,  *   E-mail:  jerry@ua9ar.urc.ac.ru
>       Chelyabinsk, 454080, Russia   *

>From Frank Donovan <donovanf@sgate.com>  Fri Aug 18 03:58:40 1995
From: Frank Donovan <donovanf@sgate.com> (Frank Donovan)
Subject: Beverages
Message-ID: <Pine.OSF.3.91.950817224745.25930D-100000@jekyll.sgate.com>

Hi John!

Rhombics must be installed more than 1/4 wavelength above the ground 
(typically much more!).  As a result, their principle of operation is 
fundamentally different than a Beverage...  The Rhombic antenna (in its 
common configuration) is horizontally polarized, and its radiation angle 
is a function of its height above ground, just like a Yagi!  By the way,
Lew K4VX is a well known contester with a Rhombic antenna!

Beverages, on the other hand, are typically installed at heights of .05 
wavelengths and preferably .01 wavelengths or less.  They are vertically 
polarized, relatively inefficient (but techniques are available to improve 
Beverage efficiency to make them viable for transmitting), and the ground 
is so closely coupled into the antenna that it really becomes a part of 
the antenna!


On Thu, 17 Aug 1995, John Unger wrote:

> Frank -- This discussion on beverages has made me wonder why
> we don't see more contest stations with rhombics (not on 80
> or 160...).  Is it because a rhombic even for 20 has to be so
> much higher off the ground than a beverage antenna? I'm sorry
> if this is a dumb question, but it just seems like if you are
> going to stretch out lots of wire, it would be nice to be able
> to transmit into it, too.
> 73 - John, W3GOI

>From Frank Donovan <donovanf@sgate.com>  Fri Aug 18 04:15:14 1995
From: Frank Donovan <donovanf@sgate.com> (Frank Donovan)
Subject: Phased Beverages! (was: EVE vs Bever
Message-ID: <Pine.OSF.3.91.950817230042.25930E-100000@jekyll.sgate.com>

Hi Dave (K5GN)!

I gess u have now discovered that my real love in this hobby is 
(surprise...) antennas!

GN> This sounds like a lot of work. (removing and reinstalling the 
Beverages every year!)

It is!  But it only takes two days to install and one day to take 'em 
down and store them for next October!

LPL> >I add two foot fiberglas extensions to the top
LPL> >of seven foot steel T-posts.

GN> Fiberglas?  We have used PVC tubing for some, and currently are using 4x4
GN> wood supports for permanent installations.

Yes...  fiberglas fence posts (3 feet long) are readily available from 
Southern States.  They can be attached to the top of a steel fence post 
with a hose clamp.

GN> T-posts?  I assume you are referring to the usual fenceposts.  Are you 
GN> using single-wire beverages?

Yes... normal fence posts (T-shaped cross section) used by farmers.
My Beverages use single wires (not the dual wire reversible configurations).

GN> One more question, do you find that a slight bend in the middle of the
GN> beverage messes it up much? For example, the bev starts with 300 ft at 40
GN> degs. azimuth, then finishes (however much, say 400 more feet) at 45 
GN> degs.
I doubt that a five degree error will have a significant effect...
Purists may disagree...

GN> One more modeling/performance question.  Most models assume flat 
GN> earth.  But we all try to find locations on hill tops.  What about 
GN> Beverages that run down a hill?

Local terrain irregularity will degrade (certainly not improve!) 
the sidelobe performance of a Beverage!  Sloped but otherwise regular 
terrain is probably not too bad...  (the slope should reduces the angle of 
radiation by the slope angle).  But if u have no choice but to place ur 
Beverage over irregular terrain, do the best u can!


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