[Antennas] matching question

[Gary K9GS]

Hi Chris,

Without modeling I can guess that it would work rather poorly.  Once the length of a vertical exceeds ~5/8 wavelength many high angle lobes start to develop.  Look in any antenna book and you'll get an idea of the pattern.  I think a 3/4 wavelength antenna has a peak lobe at ~45 degrees.  a 500 ft tall antenna is pretty close to 3/4 wavelength on 160M.  Remember, AM broadcast antennas aren't designed to be good DX antennas (low radiation angle)...they are designed to put out a good ground wave signal and serve the local area.

Probably a much better solution would be to hang antennas from the top.  Maybe a sloping dipole?

73,

Gary K9GS
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K9GS
Gary Schwartz           email: k9gs (at) arrl.net
Check out K9NS on the web: http://www.k9ns.com
Society of Midwest Contesters (SMC)     http://www.w9smc.com/
GMDXA http://www.eng.mu.edu/gmdxa/
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  ----- Original Message ----- 
  From: Chris Boone 
  To: ham-antennas at yahoogroups.com ; 'Reflector Antennas Qth.net' 
  Sent: Sunday, February 15, 2009 9:08 PM
  Subject: [Antennas] matching question


  Have a chance to use a 500ft tower (Broadcast) for the 160m CQ SSB contest coming up..it does have the 120 radials under it and the station is currently running on one tower at 250watts.They have no money to finish out the matching to the new tower, etc so it is not used right now.I am curious as to what this will present on 160mtrs?? Can someone model that for me and let me know say 1800, 1900 and 2000kHz?? Plan is to put the tuner at the base and run RG 8 back to the rig..

   

  Thanks

  Chris

  WB5ITT



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