Hi Jerry,
Good time to get on the band -- things are really getting hot!
At 10:07 AM 2/5/05, you wrote:
>I'm spending the winter devoloping a plan for my first attempt at getting on
>topband in 2005. I've been reading ON4UN's book, plus K1ZM's book with the
>photos of some of you. This topband reflector has also been of help... thanks.
>To start with, I want to try shunt feeding my 45 foot tower, plus one or two
>beverages for receiving. I have a few beverage construction questions that I
>hope are not too basic (numbered for convenience in answering):
>
>(1) I was planning to run 50 ohm coax with the rest of my feedlines, from the
>shack out 50 feet thru underground PVC pipe.... to an Ameritron remote
>switching unit in a box at my tower base. As these are receive only, can I run
>RG59U from the box to each beverage without "mismatch" degradation? Or should
>I use RG59U the entire distance?
Either impedance should work fine. If you are a purist, you can use matching
transformers but the loss of the transformer might just equal (or exceed) the
slight mismatch of the coax. I have used both 75 ohm and 50 ohm, either works
fine.
>(2)Are the distances from my tower to the feed point for each beverage
>important? Is there a minimum distance I should observe?
The tower will tend to couple noise -- precipitation static, line noise, etc --
into the Beverage. But if you don't have room to separate them, you do what you
can. Ideal separation might be a half-wavelength -- but even greater distance
might have some coupling. I have a phased pair of 935-foot Beverages toward JA
that run within 10 feet of one tower and 20 feet of another (my TX vertical for
160) and this pair tends to be noisier than most of my other Beverages.
However, it is still my best receiving antenna for JA. A single 500-foot wire
that is a couple of hundred feet from the towers is quieter but generally the
phased pair still hears better even with the additiional noise.
>(3) Will wire antennas minimum 40 feet above a beverage significantly degrade
>performance of either?
I have run Beverages under delta loops (only a few feet above the Beverage)
and other wire antennas with no obvious degradaton. Again, wider separation
would be better because there is probably some coupling. But I have found the
first priority with Beverage placement is to put the antenna in the desired
direction and as long as possible (up to a wavelength or two) -- then worry
about keeping it separated from other antennas. So if you don't have room to
move the antenna away from the tower AND keep it in the desired direction, let
it be near the tower. An exception to his was one set of phased Beverages that
I tried running under the power line feeding our house. There was just too much
noise coupling -- so I finally shortened the wires from 760 feet to 465 feet to
keep them at least 50 feet from the power line. Now this is a very quiet
antenna.
>(4) Is there a minimum distance that I should separate the beverage feedpoints?
I have run as many as three to a single feedpoint, with relays there for
switching, and grounded the unused wires. I have piggybacked the control
voltage on the feedline. They worked, but more recently I have used separate
feedlines on all my Beverages and try to keep them separated at least the
height of the Beverage (10 feet is typical) though usually twice the height.
>(5) How important is it for a beverage to run in a straight line?
I have an 880-foot, 10-foot high Beverage to the southeast that is in a
straight line. I recently added a 1000-foot, 4-foot high Beverage in the same
direction but it follows the property line -- which the surveyors aptly
described as "following 18 courses along a meandering ditch." In other words,
this wire zig-zags along its length. But the "average" works out the same as
the straight-line Beverage. I have run numerous A/B tests on these two and
performance seems to be identical; the lower one might be just a bit quieter.
>(6) I've been reading that beverages perform differently at different heights
>above the earth, but does it matter very much if the height above earth varies
>along the length of the beverage, say, between 6 and 12 feet above earth?
Again, think of the "average" height of the wire. ON4UN wrote about doing this
with a single support point at the center of the wire, with the ends sloping to
ground level. I keep all of mine at a constant height above ground instead, but
occassionally a tree will fall on the wire bring it down to ground level. They
still work fine.
>(7) I think I understand about tapering down at the ends to avoid noise from
>vertical components, but what would be a good minimum from the ends to start
>the taper?
I have tried them both ways -- with tapered ends and straight-down ends -- and
can't tell any difference. W8JI has found the same thing. It's nice to keep
them above head (and deer) level so I don't walk into them while walking
through the woods (and I have a lot of wires in the woods!).
>(8) Is insulated wire better or worse than bare?
W8JI did some tests and found no difference. I decided to test this with the
new SE Beverage I mentioned above -- the 1000-footer is bare aluminum electric
fence wire, no. 18 I think. The 880-footer is no. 18 insulated wire. And they
work about the same. Most of mine use insulated wire -- no. 12 THHN house
wiring type -- simply because I can get it cheap from local scrap yards and it
is pretty durable when trees fall on it.
>(9) If I use insulated wire and trees as supports, can I just staple the wire
>to the trees? Or should I use an insulator? If an insulator, is the standoff
>distance from the tree significant to performance?
Trees tend to make great insulators. If I'm in a hurry I'll just toss the wire
over tree limbs. Where they aren't in the right spot I'll use electric fence
plastic insulators, driven into the tree with a nail. The downside of these is
after a couple of years the tree will grow around the insulator and wire. So a
better way for longterm use might be to use a short 2x4 to keep the wire off
the tree.
>(10) Aside from durability concerns, will I get better performance from #14 vs
>#22 wire? Or stranded vs solid wire?
No difference -- wire is wire. The size will make a miniscule difference in the
impedance of the antenna.
>(11) I hope to eventually put in several beverages, but will start with 1 or
>2. I'm in eastern PA on top of an east/west ridge, so beverages will slope
>gently downhill towards the north. I'm thinking first, a 500' NE/SW for EU.
>Second one could be 500' NW/SE. After that I don't know, but are these two a
>good way to start out?
Going back to my first priority of Beverage placement -- put the wire in the
desired direction, and add to that to use a terminated Beverage to make it
unidirectional. If you want to receive both NE/SW from the same wire, run a
feedline to each end and switch it using control voltages piggybacked on the
feedline. Or use a 2-wire, reversible Beverage. Northeast is certainly my first
priority of directions -- lots of Europeans, Mideast and central Asians in that
direction. NW is good too -- JAs coming through many days right now.
73/Jon AA1K
Felton, Delaware
www.aa1k.us
>Any ideas or suggestions will be appreciated.
>
>73, Jerry K3BZ
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