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On Wed, 21 Apr 2004 20:47:47 GMT, zeno wrote:
Although I have the acres (7) there are a lot of buildings (old barns etc.), trees, etc. My antenna planning has to dodge many many obstacles actually. This is an old chicken ranch and there are building everywhere, then all the trees. Are you saying that a rhombic could be put up on the same masts more or less (only one of the masts is potentially moveable, meaning that it would only be diamond like at one end of the trapezoid. This rhombic would be instead of the 540' loop? I will look up rhombic in the books and see what gives. Hi Bill, No, this time shape matters as it is a function of all angles of radiation combining to ADD rather than jumble. Again, think in terms of the supports/mast merely being the outer, irregular perimeter to an ordered interior antenna shape. The Rhombic would BE the 540' loop. Normally it is open or terminated at the end opposite the feed point, but having the shape anticipated is more the work than this simple change. (It has the same feed considerations, complete with your expected twin lead.) Congrats on your desired call. 73's Richard Clark, KB7QHC |
for starters a good contest alternative: Toronto Alaska Japan
and for the hometown crew: Tasty Apricot Jelly or Typical Antique Junk Cecil Moore wrote: zeno wrote: Hey I got it!!! I am now K6TAJ, Tango Alpha Juliet. Now we will have an endless thread of words to match your TLA (three letter acronym). Transmitting All Joules? -- 73, Cecil http://www.qsl.net/w5dxp -----= Posted via Newsfeeds.Com, Uncensored Usenet News =----- http://www.newsfeeds.com - The #1 Newsgroup Service in the World! -----== Over 100,000 Newsgroups - 19 Different Servers! =----- |
The problem, as I see it, with using the fixed masts as outside perimeter
configuration support structure for the specifically ordered interior shape is the sag the inevitably occurs when wire is a rope and pulley distance away from the supporting mast. I already see this with the tree supported antenna. The ropes drop down and the wire is 8' or so lower than anticipated. This seems critical when the masts are only 50' to begin with. How high, or shouls I say, what is the minimum height for an acceptable Rhombic? Bill, K6TAJ Richard Clark wrote: On Wed, 21 Apr 2004 20:47:47 GMT, zeno wrote: Although I have the acres (7) there are a lot of buildings (old barns etc.), trees, etc. My antenna planning has to dodge many many obstacles actually. This is an old chicken ranch and there are building everywhere, then all the trees. Are you saying that a rhombic could be put up on the same masts more or less (only one of the masts is potentially moveable, meaning that it would only be diamond like at one end of the trapezoid. This rhombic would be instead of the 540' loop? I will look up rhombic in the books and see what gives. Hi Bill, No, this time shape matters as it is a function of all angles of radiation combining to ADD rather than jumble. Again, think in terms of the supports/mast merely being the outer, irregular perimeter to an ordered interior antenna shape. The Rhombic would BE the 540' loop. Normally it is open or terminated at the end opposite the feed point, but having the shape anticipated is more the work than this simple change. (It has the same feed considerations, complete with your expected twin lead.) Congrats on your desired call. 73's Richard Clark, KB7QHC |
On Thu, 22 Apr 2004 00:20:50 GMT, zeno wrote:
The problem, as I see it, with using the fixed masts as outside perimeter configuration support structure for the specifically ordered interior shape is the sag the inevitably occurs when wire is a rope and pulley distance away from the supporting mast. I already see this with the tree supported antenna. The ropes drop down and the wire is 8' or so lower than anticipated. This seems critical when the masts are only 50' to begin with. How high, or shouls I say, what is the minimum height for an acceptable Rhombic? Hi Bill, Think positively: how high will they be? 40 Feet? 10 Meters? One quarter wave for 40M? This is not a hardship case. One half wave or better high for 20M and above? No one's gonna let you cry in your beer there either. And now for the classic "testimonial": it's gonna be boomin! (what choice do you have?). As a cautionary, don't try to pull out the catenary. The tension rises with the tangent of the of the deflection angle. If you could achieve perfect flatness, a breeze would snap the line. 73's Richard Clark, KB7QHC |
ladder line construction methods?
What are the units of distance? Inches? CM? MM? For 300 ohm ladder line, I get .390. Thanks On Tuesday, March 30, 2004 at 8:43:04 PM UTC-5, Tom Bruhns wrote: Impedance is about 120*ln(2*D/d) ohms, where ln is the natural logarithm, and D is the wire spacing, center to center, and d is the wire diameter. Assumes round wires, and air dielectric. You can rearrange that: if you want x ohms and have d diameter, D = d*exp(x/120)/2, where exp(x/120) is "e to the x/120 power". If you don't have a calculator that handles that sort of math, this table will probably get you close enough: D/d impedance, ohms 1.9 150 2.8 200 6.2 300 22 450 75 600 Construction depends a bit on how much you're making and what you have available for materials and tools. People used to use wooden spacers, boiled in parafin wax. Someone gave me a bunch of PETE tensile-strength test strips that are a good size. You can make spacers from PVC pipe. You can thread wires through holes (generally not so efficient), or fit wires into notches and secure by with a plastic or wire wrap, or by melting the wire into an undersized notch, or with various glues. Undoubtedly lots of other ideas, both tried-and-true and just waiting to be tried for the first time. You can drill holes through the glass and install feedthroughs (but probably not if it's double-pane!), or drill a couple over-size holes through the wall or possibly through a wooden window frame member, or install a wood or plastic piece in a partially-open window. You can also possibly inductively or capacitively couple through the window. If you decide to go through wood or wall materials, plan to make oversized holes, lined with decent electrical/RF insulation. What strikes your fancy? Cheers, Tom Larry Gagnon wrote in message ... Hello to all. I intend to erect an 80 meter full size dipole and feed it with homebrew open ladder line. Would anyone care to reply as to how to construct ladder line easily and effectively? How does one determine spacing to get X ohms impedance line? Also any ideas on how such line can easily be fed in through a window with a wood frame would be greatly appreciated. Larry Gagnon VE7EA |
ladder line construction methods?
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