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[TowerTalk] A3/A4 tuning information

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Subject: [TowerTalk] A3/A4 tuning information
From: John Crovelli <>
Date: Sun, 23 Oct 2011 18:08:11 -0400
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John KK9A et al.
Some additional information.  This is a brand new A4 antenna right out of the 
box from Cushcraft.  The direction of the traps was clearly marked with 
stickers and all traps were properly installed in the right direction.  And 
npne of the traps from the A4 had drain holes (an obvious mfgr error) but the 
TK traps for the 40M addon kit did have the holes drilled.  
Further, in shipment, over half of the SS hoseclamps were deformed/crushed.  
Had to buy six new ones to replace clamps that were not salvageable.
The antenna is mounted in the clear at least 35 feet above a roof on an HDBX 48 
foot tower.  There are no other antennas we can pretty much 
eliminate interactions of any kind.
Using the factory dimensions for tuning the DE for either 'center' or 'CW' that 
come with the A744 40M addon kit,  the bandwidth was only about 180 khz on 20M, 
350 khz on 15M, and maybe 500 khz on 10m, but in no case could I get the 
minimum SWR where I wanted it so the antenna would provide both cw and phone 
On 40 meters there was 120 khz of bandwidth, what I expected, and it had a 
minimum at 7055 which was what I was looking for.
There are four possible points of adjustment on each element half.  The maximum 
adjustment on each element half (between the 'center' and 'CW' options per the 
manual ) is 14 inches.  
Since I could not hit the desired sweet spot frequencies on any of the bands 
using the factory settings, I strongly suspect the traps are not tuned to the 
proper frequency for the dimensions provided.   One or both of the TC and TD 
traps are potentially defective from the factory.  This would account for the 
inability to hit the desired mid-point frequencies in the SWR curves, and the 
lack of overall bandwidth on 15 and 20, etc. where there should be nearly 500 
I have assembled and installed more than a dozen A3/A4 + A744 addon antennas so 
I'm very familiar with their assembly and installation.
I'm looking for info from anyone who might have had this same experience and/or 
opinions of others what might be wrong.  I have received several off line 
resonses so far, one of which confirmed the antenna should have nearly 500 khz 
of bandwidth, particularly on 20 and 10 meters.
And no, I don't have the traps in my possession.  They are still on the antenna 
which is currently mistuned in the air at 50'.
John Crovelli W2GD/P40W

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