Topband: Bi-directional Beverage for DXpedition

[Ron Feutz]

Topbanders,

I need the advice of experienced Beverage builders regarding construction 
of a bi-directional Beverage system for our upcoming CQWW CW trip to J7 
Dominica.

The antenna will be made of 300 ohm ladder line from Wireman and the 
transformer/termination are the K1FZ boxes.

On previous trips, a single wire Beverage was installed using an ICE 
Beverage transformer and termination resistor.  The antenna was ~600' and 
pointed right at EU (broadside to US).  The antenna was useful but 
apparently did not have the expected directivity, as it performed about as 
well for US contacts on 80 and 160 as did the corresponding transmit 
antennas.

The RG58 feed line, about 100' long, ran right to the shack with no 
grounding (other than the feed point and termination ground rods), or 
common mode suppression.  The antenna had single re-bar ground rods, 
pounded into the rocky soil about 3' , at both ends.  I suspect the ground 
is extremely poor, as the QTH is high on a cliff of volcanic rock.  I 
suspect that a main cause of lack of directivity is feed line 
pick-up/common mode currents on the feed line.

My intention was to construct the feed lines per ON4UN's specs (pg 7-19 of 
his latest book).  I was foiled by the inability to make the Wireman beads 
I bought fit on the coax (tried 2 types of coax - Wireman house brand and 
Belden).  I had to get that stuff shipped ahead, so I just put the 
connectors on the lines and packed them up.

I have provided 4' copper plated ground rods, and intend to use one (or 
two) at the feed point, one twenty or so feet down the line, and another at 
the shack entrance, per ON4UN.  Since the lines will not have beads, my 
alternative is to provide some other type of choke.  ON4UN says mini coax 
wound on a stack of cores, but doesn't specify a manufacturer or model 
#.  Being under time pressure, I would appreciate a recommendation on this 
to save me doing more homework - I have plenty more to do already.

Here are my questions:

What will give me the greatest bang for the buck (effort) in improving the 
antenna's directivity?

         Improved grounding at the feed point? I can put out 2 or maybe 3 - 
4' ground rods.  Would some short radials help?

         Is there any advantage to using improved grounding at the far end?

         Common mode suppression on the feed lines.  I intend to put a 
ground rod 20' from the feed point and another at the shack entrance.
         Will this be effective with out some sort of choke?

         What core(s) should I get to make a choke of mini-coax?

         Is it practical to simply wind a choke out of RG58?  If so, what 
are the specs.

         The K1FZ system uses separate feed lines for the two 
directions.  Do I create any problems by grounding both shields to the 
same        ground  rod(s).

Thanks in advance for the help and advice.

73,

Ron - WA9IRV

PS  Please, I know most if not all of this info is available in various 
archives and references.  I am merely asking the opinions of experienced 
Beverage builders as to what will work best in this situation





Ron Feutz, WA9IRV
Air Communications of Central Wisconsin, Inc.
715-424-3050 days
715-423-7662 nights
715-572-3621 cell