It is important to realize that a cage just hung of the side of a steel
tower has some drawbacks. The pattern when modeled is somewhat
asymmetrical to a slight degree. In a properly designed cage feed it is
the cage that does the radiating and not the tower. (Above the cage is
mainly the voltage part of the radiator.) This is also important
because the tower downwind of the cage may interact. With a symmetrical
cage around the tower that is not the case. Also another advantage of
the symmetrical cage is the reduction of RF pickup on rotor wires, coax
feed lines to other antennas, and certain control lines for switching.
Jeff's intentions were good in pioneering the "easy cage"idea. But one
thing that may influence some people are the aesthetics of a beautiful
four wire symmetrical cage to something hanging of the side of your
tower. But for me the most impressive was the ease of installation as
compared to the list of material required in the asymmetrical cage.
There may also be a slight increase of bandwidth with a symmetrical
cage as claimed by some.
Herb Schoenbohm, KV4FZ
On 12/18/2015 1:44 PM, Robert Harmon wrote:
Gene,
The cage design sounds very interesting. I just ordered the book :-)
thanks Gene,
Bob
K6UJ
On 12/18/15 9:27 AM, Gene Smar wrote:
Bob:
I built my shunt feed wire cage based on the design in Jeff
Bigg's K1ZM book "DXing on the Edge..." I bought it from the ARRL
bookstore but you might be able to find it on Amazon, etc. I used
two widely-spaced wires whereas he used three in a triangular form
held off the side of his tower with PVC pipe. I was surprised at how
well it seems to work for me ( I always get through and receive good
reports.) Good luck.
73 de
Gene Smar AD3F
On 12/18/15, Robert Harmon wrote:
Stan,
With shunt feed I would gain the 18 foot mast with the yagis, the total
overall height is 108 feet.
I haven't really considered shunt feeding. I see your point of the
wires with an L in proximity to other
antennas. That was a worry I had with the 40 meter yagi and the L. I
will look into shunt feeding. I have ON4UN's book, probably should
start there to bone up. Any other resources to learn abut shunt
feeding ?
The top band archives probably has a lot of discussions about shunt
feeding also.
thanks Stan,
Bob
K6UJ
On 12/18/15 1:36 AM, Stan Stockton wrote:
Bob,
There is no reason I can think of to not shunt feed the tower as it
is with either ground radials or elevated radials. An inverted L
isn't as good as a vertical for DX and you would just be adding
clutter and horizontal wires in proximity to your other antennas.
Shunt feeding a tower is very, very simple.
73... Stan, K5GO
On Dec 17, 2015, at 8:06 PM, Robert Harmon k6uj@pacbell.net> wrote:
I am planning an install of a 160M inverted L and would like
critique from you top banders.
I was originally planning a separate tower for 160 but my XYL has
squashed the idea :-)
My tower is 90 feet fully extended with a 18 foot mast currently
used for a Force 12 WARC plus 10/15 beam
on top and a N6BT DXU-32, 2EL 40 and 3EL 20 12 feet below.
At the top of the top section I have a 10 foot fiberglass pole I
plan to extend out to support the vertical, so it will be 10 feet
away from the tower.
I am thinking of feeding the vertical and having 4 elevated radials
at the 14 foot level.
So the vertical wire will about 76 feet long.
I am wondering if I would be better lowering the feedpoint & radial
tie ins down from 14 feet say to 8 feet and have more length in the
vertical portion of the L or better to have the 14 feet elevation
for the radials ?
Also the horizontal leg of the L on top will be about 5 feet below
the 40/20 yagi only 10 feet out from the tower,
do you think this is OK as far as interaction between the yagi and
the 160 L ? Anything else I should consider ?
I have never had a decent 160 antenna, just hoping I can work
something out with my existing situation
thanks in advance,
Bob
K6UJ
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