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[TowerTalk] Fw: Tennadyne LPDA

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Subject: [TowerTalk] Fw: Tennadyne LPDA
From: (Dave Karklin)
Date: Sat, 4 Apr 1998 12:22:54 -0500
Wonder if anyone experienced high SWR with a T-10 log periodic.  Mine is
mounted in the clear at 120 feet and fed with 50 ohm coax through a 1:1
balun per Tennadyne's specs.  SWR using an Autek RF-1 varies from 1.6 (at
18.07 and 21.45) to 3.2 (at 28.4).  The balun has been ruled out as a
cause.  This is an older style T-10 which uses two 2 inch booms to provide
out-of phase current to each half element.  Boom centers are spaced 3.75
inches apart -- which ARRL Handbook formulas indicate should not work well.

Modeling this antenna using Nec/Wires (with 900+ segments) confirmed
significant excursions in feedpoint Z and SWR.

Since purchasing this antenna several years ago, Tennadyne changed the
booms from round to square and positions them closer together.  The
designer is not willing to share his calculations or admit that the booms
were changed due to performance problems. 
1)  Has anyone experienced similar problems with this antenna?
2)  Has anyone modelled this antenna?
3)  Any suggestions on how to improve its performance?
Thanks for your help.                                               73,  
Dave  W2TA

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