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Re: [TowerTalk] A3/A4 tuning information

Subject: Re: [TowerTalk] A3/A4 tuning information
From: W0MU Mike Fatchett <>
Date: Sun, 23 Oct 2011 17:53:43 -0600
List-post: <">>
The only comment I have is that it is an MFJ product now.  I wonder if 
those traps have the same issues as the coils on the new XM240  ie the 
screw coming loose and bad connections.

Mike W0MU

J6/W0MU November 21 - December 1 2011 CQ WW DX CW
W0MU-1 CC Cluster

On 10/23/2011 4:08 PM, John Crovelli wrote:
> 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 coverage.
> 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 
> khz.
> 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'.
> 73,
> John Crovelli W2GD/P40W
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