On Thu, 9 Oct 1997 07:01:22 -0400 (EDT) Frank Donovan
<donovanf@sgate.com> writes:
>Rick,
>
>A few ideas in response to your query...
>
>I do not use multiwire Beverages, but you will probably get additional
>comments on this topic.
>
>First, I don't think a metal fence will affect a Beverage so badly
>that
>you need to keep 200 feet away.
As long as the fence is not acting as a radiator at the desired
frequency. Most metal fence posts are in concrete which is a insulator.
I know of some who use a fence successfully as a RX antenna.
Ground the fence if necessary at several points.
Many measurements on adjacent
>Beverage
>antennas indicate that separation at least equal to their height above
>ground (eight foot separation for Beverages eight feet high) is
>adequate.
>more is beeter, but 200 feet separation to a fence line should not be
>necessary.
That 200' + seperation is suggested by many from a TX antenna or tower.
My SW wire Beverage runs between insulated guy levels of the tower (about
100' from the base) and under the radials of the TX antennas. It still
seems to work well.
>The issue with the feedline is mostly isolation of signals flowing
>on shield from the ground terminating the feedpoint of the
>Beverage. Any signals induced onto the shield will cause current to
>flow
>in the ground system, which then create a voltage in series with the
>signals coming off the Beverage. There are several steps to minimize
>these undesired shield currents. You do N O T need to incorporate
>all
>of these steps, many successful systems use none!
>
> - Bury the feedline (usually impractical!)
> - Use an excellent ground (multiple ground rods with B U R I E D
>wires
>interconnecting them
If a good ground rod installation is not possible run a 135' ground wire
from the feedline end and directly under the Beverage; do not connect the
far end to anything. In my case solid rock is only 8-24" down. I use a 8'
industrial/utility grade rod driven in at an angle and the counterpoise
wire. DO NOT use a Rat Shack or equivalent rod.
At the far end I use another angled rod and with 3 135' wires on the
ground; one directly in line with the antenna and one on each side at
about a 15 degree angle.
The above works well for my poor ground QTH and brought the F/R in line
with published plots.
> - A matching transformer design with inherently good isolation from
>currents on the feedline shield
Frank, do you mean seperate ground wires for the feed and antenna
windings? Explain please. I use a 9:1 xfmr and tie both ground leads
together in the box and run a single #10 wire to the rod.
> - Isolate the feedline shield from the matching transformer with
>ferrite
>beads
> - Install a second ground rod -- isolated from the transformer -- to
>ground the shield. Some even uise a third ground rod ten ot
>tweenty feet down the feedline.
As above, I'm not clear on this.
Running standard coax on the ground can be a problem for some. I lost
several runs of RG-6 and RG-11 CATV cable to animal bites. Since then I
use CATV hardline for any on the ground run. An alternative would be to
buy a 1000' reel of quad shielded and flooded RG-6 from a distributor
(under $100) and share the expense. The critters don't like the flooding
compound.
Others have reported losing runs of RG-213 from moisture migration
causing the shield braid to go green and causing BC band IMD.
There is no free lunch after the initial DXCC! It gets harder and
harder.
73 Carl KM1H
>Good luck!
>73
>Frank
>W3LPL
>donovanf@sgate.com
>
>On Wed, 8 Oct 1997, Richard Karlquist wrote:
>
>> I have been reading up on Beverage antennas, but have not seen much
>> about proper routing of the feed line to the Beverage. I gather
>that
>> you obviously don't want to run it directly underneath and parallel
>to the
>> antenna, but can it be in parallel and spaced away some distance? I
>> read that the antenna should be 200 feet away from wire fences. Is
>> this also true for coax, or can it be closer that 200 feet due to
>being
>> on the ground? I have seen a technique where a 2 wire beverage is
>used
>> with transformers at the end so you can run the coax from either end
>and
>> utilize both directions. Is this technique in general use or is it
>too
>> temperamental (or unnecessary)? Can the deleterious effects of coax
>be
>> mitigated by inserting choke coils in the coax at regular intervals
>to
>> prevent currents from flowing on the outside of the shield? What
>spacing
>> would be needed?
>>
>> Rick Karlquist
>> N6RK
>> rick@area.com
>
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