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一个很小和天线计算程序

Continued from previous posting:   part 3


    Cubical Quads: (Mono band, armstrong rotor, etc)

    This antenna can be a real hoser if not constructed correctly
    the first time. Preps on this antenna are a must. Spreaders must
    be checked and elements also.  There is nothing worse than getting
    to the field day site and having difficulty with a Cubical quad.
    A strong antenna but a real pain in the butt raising and lowering 
    to adjust, especially in the rain. Like a box kite, this antenna
    does lend itself to the wind. Whether you use the D/DE or DE/R 
    configuration, it makes no difference. 

    This is a homebrew antenna for the most part.  There is very 
    little in the commercial source market for these antennas. So, get
    your sh** together early if you want to use a Cubical quad on 
    field day. 

    Assemble per your design and test per the yagi directions. 
    Cumbersome as it is, this must be done. Mark all connection points
    and if possible, use expanding spreaders and wire clamps on the 
    ends.  IF you use a tuning arm, be sure it's protected in the
    correct position and can be easily re-adjusted if required.  

    A cubical quad can fold down into a very neat package, but that
    will take some forethought on your part.

    ==============================================================

    Inverted Vees: (fixed, mast support or improvise)

    An Inverted Vee *may* tune fine at home and then be out to lunch
    at the Field day site. Using the tuning extentions I posted for 
    Inverted Vees will solve any problems relating to this.  Why this 
    happens is that at home the IVee is interacting with Guy wires or
    other wire antennas or something in the imediate area of the 
    antenna.  At my home, the roof flashing does not require a tuner
    when used as an antenna on 40m. I found this out by accident.
    Thus, my 40m inverted vee was very difficult to tune. So was a
    15m yagi I had once. Solution: I grounded the roof flashing. 

    Select a clear open area to cut, assemble and test the antenna.
    Once this is accomplished, the IVee should work just fine.

    Hints: Raise and lower the antenna using a rope and pulley. You
    can attach a rope & pulley to the mast prior to raising and 
    securing the support. Use rope as guys rather than cable.

    A wheel & tire from a car make an excellent mast base when combined
    with a clamp & flange assembly.  This appeared in QST I believe
    about a couple of years ago.  Any good mast base will work and 
    I have used plywood and a hinged base support many times.

    If you can, use a 1:1 BALUN.  Hook ups are easier and so is raising.

    =================================================================

    Wire Dipoles: (fixed, mast or rope support)

    Pretty much like the Inverted Vee, prepare ahead.  Similar
    problems may happen so test in an open area.

    At the site, determine where the antenna needs to face and then
    pick out the best supports. If using masts, set up similar to 
    a large volley ball net (very large).  The farther apart the 
    supports, the more the rope will sag if no center support is used.
    On 10m and 15m this is not too much of a problem. By the time you
    get to 40m and below, the sagging is a big problem.

    I will suggest the wire dipole be supported in the middle and
    the ends held out with rope.  Set up similar to the Inverted Vee.

    Use a 1:1 BALUN.
    ==================================================================


-WS