[SJDXA] Work Party Re-schedule 11/07

[John Crovelli]

Hmmmm the Good GD....you may have to wait in the P40W CQWW CW pileups later this month OM......
 
Anyway,  many of you probably know we've have had pattern problems with the two ele. 160 transmit array since the WYRS/WSC tower was renovated with unbroken and grounded guys a few years back.  Field strength readings taken last January 3 miles from the station in the NE/SE/SW/NW directions confirmed we had big problems, and essentially no gain at all to the west.  
 
Last month W1GD picked up the ball for all of us and ran nearly two dozen computer models of tower and antenna configurations using the EZNEC modeling program in the hope of finding what set or sets of guys were doing the most damage to antenna performance.  
 
Fortunately we learned through modeling that the forth set of guys at 160' were apparently 'hot' causing the majority of the pattern distruction.  When these guys are ''removed'' from the model, the expected pattern to both NE and West directions is nearly completely restored to the projections seen in our original antenna design models done by K2TW nearly 7 years ago (e.g. 6+ db of forward gain which isn't bad on 160M).  
 
So there were three possible solutions:  do nothing and live with the problem, replace the 4th set of guys with Phillystran, or break up the 4th set of guys into non-resonant lengths using insulators.  Since Phillystan costs ~$1.80/foot and with preforms the total bill would come to $1K,  we proposed to Bob inserting two insulators in each of the guys, one near the tower at 160', and the other 90 feet up from the ground.  This results in 10'/186'/90' segments of 3/16 inch EHS steel which are non-resonant on 160M and make the 4th set of guys electrically invisible to our antennas.....at least the model says this is the case.  It took about 5 hours of effort to get this work done today and we look forward to finding out next month in the ARRL 160 Contest.  
 
We also repaired the 160M vertical dipole hung from one of the 60' self supporting towers (the top rope holding the antenna up had finally broken after 5+ years of exposure.  The black dacron installed should last somewhat longer.
 
We need SJDXA help Sunday in the marsh to get the antenna up.  It takes at least 4 people out there to efficiently put this BIG antenna up, so having one or two SJDXA members helping Marty, Tom and Gerry will make things go much more smoothly.
 
And we also have feedlines to 6 beverages to install among other things.  More hands makes the work go quickly.  Bring along a set of wire cutters, knife, etc.
 
TNX and 73,
 
John W2GD 
 

 

 



To: w2cg at comcast.net; w2gd at hotmail.com; n2oo at comcast.net; sjdxa at mailman.qth.net; k2tw at arrl.net; w2no at optonline.net; bob at wyrs.org; w2rq at embarqmail.com; rwmcgwier at gmail.com; w2fa.kgw at gmail.com
Subject: Re: Work Party Re-schedule 11/07
Date: Tue, 2 Nov 2010 19:27:13 -0400
From: w1gd at aol.com


I can be there Sunday.
 
I got to spend the day at West Creek with W2GD and K4ZA installing insulators on the 4th set of guys.  At the request of Herr General, Don and I measured the distance frrom the tower to the NE sloper anchr point. (N2HM had actually mwed the path!)  The distance was 270 feet.  We may want to move that out another 10 feet to keep the lower end of the sloper from crosing the loop.  Also, the anchor post was VERY rusty and shaky in the ground.
 
Also at the "request" of Herr General, I will send out the heights and spackings of the loop and dipoles tomorrow so we all have them.  The pulleys are in placeto put the loop and slopers at the height we've used since the original K2TW model work.  We didn't have time to check the pull ropes.
  
 
The Good GD (I heard that several times this weekend)




-----Original Message-----
From: Marty Grozinski <w2cg at comcast.net>
To: 'John Crovelli' <w2gd at hotmail.com>; 'N2OO' <n2oo at comcast.net>; sjdxa at mailman.qth.net; w1gd at aol.com; 'Marty Grozinski' <w2cg at comcast.net>; 'K2TW' <k2tw at arrl.net>; w2no at optonline.net; 'N2HM' <bob at wyrs.org>; w2rq at embarqmail.com; rwmcgwier at gmail.com; w2fa.kgw at gmail.com
Sent: Tue, Nov 2, 2010 5:09 pm
Subject: Work Party Re-schedule 11/07


All,
Let's have another try at getting together on Sunday, Nov 7.
Our priority is to erect the transmit antennas out at the main tower, and
run coax to the beverage antennas.
Extended weather forecast looks to be partly cloudy and temps in the 50s.

Please reply to all with your intentions.
Marty, W2CG