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[TowerTalk] Even more: Topband: New Antenna

Subject: [TowerTalk] Even more: Topband: New Antenna
Date: Sun, 26 Dec 2004 19:43:48 -0700
List-post: <>
  ----- Original Message ----- 
  To:<> ;<> ;<> 
  Sent: Sunday, December 26, 2004 7:38 PM
  Subject: More: Topband: New Antenna


  I thought I had better really simulate the flagpole rather than just dismiss 
it out of hand. Here are some possibilities:

  1) wire from the top of 35' flag pole to the tower, at the 35' level. Rr = 7 
  2) wire from the top of the 35' pole towards the top of the tower. Rr = 16 
  3) wire from the top of the 70' tower (not attached to the tower) towards the 
top of the 35' pole. Rr = 16 ohms
  4) wire connected to the top of the 70' tower towards the top of the 35' 
pole. Rr = 17 ohms
  5) tower feed. 16 ohms. 
  6) top load the 70' tower with a coil and a top hat or spike. Rr = 25 ohms. 
The only design that does not need the 35' pole. 

  Number 1 looks bad. Scratch that one. Numbers 2-5 all look good from a 
performance standpoint. Number 2 looks to be the simplest to implement. This 
can be fed directly with 50 ohm coax and tweaked with a good antenna tuner at 
the shack. This is the one I would seriously consider. Number 6 has the highest 
performance IF your ground system is not very good. You get 9 ohms more Rr at 
the expense of a few ohms of top loading coil loss. This one needs shunt 
feeding of the tower and is a lot more complicated to get going than number 2. 
If your ground system is good I would not bother with the added complexity of 
this one. 

  These sims are subject to having better inputs (dimensions, ground, radials, 
etc.) but I believe them to be good for comparison of the different designs. 
None of these, except for number 6,  requires loading coils. All of the rest 
are adjusted to resonance by the length of the horizontal wire. 

  BTW, I use a 38' top loaded vertical. It is all I can fit in my antenna 
unfriendly neighborhood and small back yard. 

       Dave  WX7G

    ----- Original Message ----- 
    To:<> ;<> 
    Sent: Sunday, December 26, 2004 12:29 PM
    Subject: Topband: New Antenna

    I have a question about choices on 160 meters.
    I expect to have a new home at Lake Havasu City next  summer.
    I will have a 60/70 foot fixed tower topped by a couple of  OptiBeams
    (16-4 and a 4-40).
    About 100 feet away, I expect to have a 30/35 foot flag  pole.
    What is my best way to get on 160 with this arrangement?   A couple
    of ideas come to mind.
         1)   Shunt feed the  tower
    2)   Use a wire between the top of  the tower and the top of  the
    flagpole  to use as top loading for vertical wire in the  center
    of  it.
    3)   Extend an arm out from the top of  the tower, say around  6-8
    feet and  drop some kind of vertical element to be base-fed.
    Advice is needed; please donât say I am nuts.

    Warren; W5KKW
    Topband mailing list<><>

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