[TowerTalk] Min spacing to 80m yagi ?

[Jim Thomson]

From: TexasRF at aol.com 
Sent: Wednesday, October 06, 2010 5:48 AM
To: jim.thom at telus.net ; towertalk at contesting.com 
Subject: Re: [TowerTalk] Min spacing to 80m yagi ?


Jim, wouldn't you think that the 20m yagi would suffer pattern degradation while the 80m yagi would be ok?

73,
Gerald K5GW

##  You may well be correct, but I have no clue. If I lost a couple of db on 20m.. at least it gives
me 20m capability.   Another possible config  would be to put the 20m right at the top,  with 40m
just below it, and 80m at the very bottom.   Then you get a max of 10.5' between  80+20m.   Now
whether the 80m  will then screw up the 40m is another question. 

Jim  VE7RF 





In a message dated 10/6/2010 7:35:00 A.M. Central Daylight Time, jim.thom at telus.net writes:
  How close can you get a 20m yagi, below a 2-el  80m yagi ? 
  I have an option to use a F-12  Sigma  280-S  shortened 80m yagi
  at the top of the mast, with the F-12  340N  at the bottom of the mast. 
  Spacing between the two of them would be  10.5'    If possible,  I 
  would like to sandwich my  F-12  520  [20m yagi]  between the 
  80 and 40m yagi.    Apparently, you can mount any other F-12 HF
  yagi within 36"  of the 3-el  340N yagi.    If I put the 20m yagi
  4'  above the 40m yagi... that would leave  6.5' between the 20m yagi
  and the 80m yagi.   Will this work ??    If it doesn't, one option is
  to remove the 20m yagi.   Another option is  to  place the 80 and 40m
  yagi's at right angles to each other [ no 20m yagi at all] .   I don't think this
  is required, but would minimize the total wind load. 

  Plan B  would be to replace the 2-el 80m yagi with a
  80m rotary dipole...with dipole inline with 20m/40m booms  below it.  IE: dipole
  is then at right angles to both yagi's below it.   Due to  day time height restrictions,
  the above options are strictly an after dark scenario.   I don't have any software on hand
  to model any of the above.

  Thanks.... Jim   VE7RF

      
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