On 7/24/2013 2:53 PM, Jim Brown wrote:
On 7/24/2013 11:25 AM, K8RI wrote:
The fan dipole on 75 can give much wider, usable areas.
With SS amps I'd like to be able to QSY with all the knob twisting.
Yes. It's easy to make wire spreaders by cutting 1/2-in PVC conduit into
18-in lengths and drilling holes for the wires. If one of the wires is
bare copper, the spreaders can be held in place with wire looped across
the spreader and soldered. I use hard drawn copper that I "make" by
buying #8 bare copper from a big box store, tying one end around a tree
and the other around a trailer hitch, and slowly stretching it until it
breaks. The resulting hard drawn copper has stretched by roughly 10%.
I used plain old stranded "antenna wire" that I hah on hand. I too
used 1/2" conduit for a single end spreader about out 4' long
http://www.rogerhalstead.com/ham_files/AntennaSpreader1.htm
This is fed with LMR-400 using one of the current baluns described in
your tutorial http://www.rogerhalstead.com/ham_files/AntennaFeed2.htm
That antenna is supported by ropes to large trees on the low end and a
rope through a pulley near the top of the 100' 45G. That rope is then
coiled up and tied off at the base of the tower making the raising and
lowering to prune quite easy. That antenna is under several hundred
pounds of tension.
I've been thinking of using the same approach on the 160 half sloper
except it's end fed of course.
I think these antennas with stubs might at least come close to what I
want.
I consider copperweld antenna wire a terrible choice for serious antenna
work. My neighbor, W6GJB, built a 2-wire fan dipole using copperweld and
RG8, and hoisted it between a couple of redwoods with pulleys on both
ends and a weight on one end. It was on the ground the next day -- the
copperweld broke. We rebuilt it with the hard drawn copper.
Only tried Copperweld once. Never purchased any more.
I've also used that method to "hard draw" the wire, You can also use
a lever (pipe, wood, what ever) the wire will stretch easily, but will
reach a point where the force required rises rapidly. and you don't
have to break it, although breaking does guarantee it is as hard as
it's gonna get. <:-))
The Power Point shows another elegantly simple and effective method of
broadbanding many resonant antennas that W6NL teaches in his classes at
Stanford. With SimSmith, you can simultaneously model both SWR and loss,
making it easy to optimize a design.
73, Jim K9YC
73
Roger (K8RI)
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