TopBand: 2-wire Beverages

[km1h@juno.com]

First...Im not sure that Im doing this new Majordomo thing correctly. I
thought it was verbotten to send everything to the reflector. Perhaps
Herr Administrator can correct my ways. 


I really have to thank John, W1FV,  for his response since he is one of
the top low band operators around with the wallpaper to prove it.
...something often lacking in some discussions. 

The difference between John's and my QTH are profound and might be the
core of the differences in performance. John is at a fairly low ASL
elevation and, as he said, in a fairly swampy area. I am only about 20
miles North but on the top of a hill where there is a thin (8-24" ) soil
coverage over solid granite. I have consulted with John and duplicated
his 2 wire system ....but it just dont work here!!  John....I'll be in
touch!

The one thing I have learned in ham radio in general...one size does not
fit all...no matter if someone tries to ram it down your throat as a self
appointed expert.  After 40 years, I still learn something new daily.

73.Carl   KM1H


  
On Tue, 25 Feb 97 14:25:54 -0500 kaufmann@ll.mit.edu (John Kaufmann)
writes:
>It is my experience that Beverage antennas really do want to work and
>are quite forgiving of imperfect construction techniques.  I have 
>never
>had anything but good performance from every Beverage I have tried.
>
>I currently have two 2-wire Beverages--one NE/SW and the other SE/NW,
>each about 450-500 feet long.  One Beverage is end-fed while the other
>is center-fed (actually off-center somewhat).  I have to admit the
>construction is rather haphazard, partly because of the circumstances
>of the environment.  Trees are used for supports, with one wire on 
>each
>side of the tree trunks.  Average wire separation is about 12 inches 
>but
>depending on the trees which are used, it varies from 6 to 24 inches.  
>I
>do try to avoid abrupt changes in wire spacing.  I also try to keep 
>both
>wires side-by-side in a horizontal plane to maintain good symmetry 
>with
>respect to ground, but where only small tree trunks are available, I 
>end
>up stacking the wires vertically to maintain the separation.  The 
>2-wire
>Beverages perform every bit as well as the single-wire ones they 
>replaced.
>
>My ground terminations consist of 8 foot ground rods.  I tried adding
>radials but I could not detect or measure even the smallest change in
>performance.  Local ground conditions are mostly swampy.  I tried 
>using
>reflection transformers at the ends of the Beverages, but this 
>actually
>produced poorer directivity than simplying grounding one wire directly
>to the ground rod.  My reflection transformers probably were not a 
>good
>match to the antenna but the performance is so good as is, I see no
>need to try to redo the transformers.  
>
>I routinely see 20-30 dB rejection off the sides and back. For some 
>azimuthal and elevation angle-of-arrival conditions, the rejection is
>phenomenal.  Very strong S9+20 dB signals will literally disappear
>when switching directions. 
>
>The one area in which I do take some care is in the feed transformers.
>I use the design in W1WCR's Beverage Handbook.  I have carefully 
>pruned
>each transformer to match the feedline as well as possible.  This can
>be done with an antenna noise bridge or even with an SWR bridge, 
>feeding
>the antenna with low power RF and adjusting for lowest SWR.  It should 
>be
>possible to get nearly a 1:1 match.  With proper matching, preamps 
>should
>not be necessary.  Also, because there are two feeds from the 2-wire
>Beverage (one for each direction), I use a relay to switch in a 
>resistive
>dummy load termination for the unused feed.  I use 75-ohm CATV coax 
>with
>aluminum foil shielding for feedlines.  
>
>In short, the beauty of the Beverage is that it is so simple.  There 
>are
>no critical lengths, spacings, or phasing conditions to fuss with.  Of
>all the directional antenna systems I have tried, the Beverage is by 
>far
>the easiest to get working.  I hope these comments are helpful.
>
>73,
>John W1FV
>
>
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>

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