Topband: 80m rotatable dipole load coil questions

[GALE STEWARD]

Hmm, the link didn't take! The info is on QRZ.com/VE6WZ
73, Stew K3ND

      From: GALE STEWARD via Topband <topband at contesting.com>
 To: "topband at contesting.com" <topband at contesting.com> 
 Sent: Tuesday, October 11, 2016 11:59 AM
 Subject: Re: Topband: 80m rotatable dipole load coil questions
   
Here's a link to a 80M yagi designed and built by VE6WZ.
Some good loading coil info.
73, Stew K3ND

80m 2-el Yagi

  
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80m 2-el Yagi
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      From: Grant Saviers <grants2 at pacbell.net>
 To: Ray Benny <rayn6vr at cableone.net>; "topband at contesting.com" <topband at contesting.com> 
 Sent: Tuesday, October 11, 2016 11:35 AM
 Subject: Re: Topband: 80m rotatable dipole load coil questions
  
 From a coil loaded 80m 2L yagi (bought JKantennas) and 80m rotatable 
dipole I built and reading here are some thoughts.

My rotatable 80m Tornado loaded 86' dipole at 100' doesn't have much of 
a pattern,  height is everything and at about 130' or so they really 
start to play.  The beam is at 157'.

Element gap isn't too important - wide enough to stand the voltage, 
strong, and UV durable. 2" is ok.  A fiberglass solid rod with paint 
would work, or a UV resistant plastic sleeve over the FG.  No steel or 
SS near the coil if possible.

IMO, there is very little loss difference with 1/4" tubing Cu vs Al.  
Good electrical joints are probably more important.  Coil L/D ratio 
about 1 and turns spaced tubing diameter seems to be about optimal for 
highest Q.  Any form will reduce Q, so best to avoid them and make the 
coil self supporting.  I use 
http://hamwaves.com/antennas/inductance.html for a coil calculator, it 
gives you every value you might want.

Many other issues - truss connections,  3 way truss per Lesson's 
designs, wind load calcs, etc.  My dipole truss is 2 phillystrans up to 
a 5' wide crossbar 5' up the mast.  So far no problems, but in a treed 
area with modest wind loads.  YagiMech predicts 85 mph survival w/o truss.

I'll send a coil picture offline.

Grant KZ1W


  
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