[SJDXA] Work Party Re-schedule 11/07

[w1gd at aol.com]

Full Dislosure Statement:  The names of the operators who called me "The Good GD" started with "B" and ended with "riggs".......

I want to reemphasize John's request for more help raising the main transmit antennas.  The modeling (both K2TW's and my recent) was based on specific dimensions and spacings.  While sensitivity analysis I ran showed that we have some flexibility in the spacings without giving up very much gain, we should try to install according to the optimum dimensions K2TW found.  Based on experience, it's hard for the folks on tghe loop corners (K2TW and myself) and the NE sloper (Marty) to visually maintin the spacings during erection.  We need some good eyes to help guide us as we are raising the loop and tne NE sloper.  

Per 2GD's request, here are the dimensions used for the modeling:

Loop: (The plane of the loop is 10 feet from the tower)

Apex at 171 feet
Base up 9 feet from the ground
Base is 172.8 feet long
Remaining 2 legs 183.8 feet.

NE sloper:
Upper end is 147.7 above ground
Upper end is 31 feet from the tower (20 feet from loop)
Center is 140 feet from tower (Tie point should be at least 280 feet frrom tower or at least 10 feet out from current tie point)
Lower end is 2 feet above ground
Lower end is 31 feet from tower (20 feet from loop)

NOTE:  Sensitivity analysis shows we can be slightly higher (e.g. 5 feet ) and closer to the loop (e.g. 5 feet) without sacrificing more that a coiuple of tenths of a dB).

SE sloper:
Upper end is 147.7 feet above ground
Upper end is 11 feet frrom tower (20 feet from loop)
Center is 120 feet out from tower
Lower end is 2 feeet above ground
lower end is 11 feet frrom tower.

NOTE:  Sensitivity analysis shows we can be slightly higher (e.g. 5 feet ) and closer to the loop (e.g. 5 feet) without sacrificing more that a couple of tenths of a dB).


Before we go out to the marsh, we should double check the loop leg lengths.  

If I did my geometry right, the rope used to tie the upper end of the NE sloper to the pull rope at the loop apex should be about 31 feet long! However, I recommend that we make the sloper higher and try something like 23 feet.

I'm always open to help/suggestions.

Gerry 


-----Original Message-----
From: John Crovelli <w2gd at hotmail.com>
To: w1gd at aol.com; Marty Grozinski <w2cg at comcast.net>; N2OO <n2oo at comcast.net>; sjdxa at mailman.qth.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 9:08 pm
Subject: RE: Work Party Re-schedule 11/07


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,
et's have another try at getting together on Sunday, Nov 7.
ur priority is to erect the transmit antennas out at the main tower, and
un coax to the beverage antennas.
xtended weather forecast looks to be partly cloudy and temps in the 50s.
Please reply to all with your intentions.
arty, W2CG  


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