[TowerTalk] 75/80 vertical

[donovanf at starpower.net]

Jim,

The tubing extension will be longer than expected because of the extreme diameter difference between the tower and the tubing.  You can use your favorite antenna modeling program to determine the correct tubing length.

My rough guess is that a four to five foot tubing extension would be required with the 60 foot tower and 28 to 30 foot tubing will be required with the 40 foot tower.

73
Frank
W3LPL

---- Original message ----
>Date: Sat, 21 Mar 2009 06:58:16 -0400
>From: jim Jarvis <jimjarvis at optonline.net>  
>Subject: Re: [TowerTalk] 75/80 vertical  
>To: towertalk at contesting.com, k9kl at centurytel.net
>
>
>Gregg,
>
>234/f says that a quarter wave on 3.8 is 61.58 feet.
>
>If it were me, I'd start putting in radials, and hook the thing up to  
>the rig, or
>an antenna analyser, to see what you've got.   Worst case, you may  
>have to
>go topside and drop in a 2' piece of tube.
>
>25g should make perfectly fine connection between sections, properly  
>bolted.
>Adding jumpers won't make it measurably better, unless the tower was  
>painted
>before assembly.
>
>I'm considering something similar, here, with 40' of 25g and a 24'  
>section of 2" mast.
>
>Jim/N2EA
>
>
>
>Message: 8
>Date: Fri, 20 Mar 2009 22:56:46 -0500
>From: "Gregg Seidl" <k9kl at centurytel.net>
>Subject: [TowerTalk] 75/80 vertical
>To: <TowerTalk at contesting.com>
>Message-ID: <B3933CD4A80D413BB0106C9BEF1F0C81 at K9KLStation>
>Content-Type: text/plain; format=flowed; charset="iso-8859-1";
>	reply-type=original
>
>Well now that most of the snow has melted its time to finish last years
>antenna projects!! My question is this: I installed 60 feet of Rohn 25
>insulated from ground. I used the tapered top section as I'm going to  
>use a
>peice of pipe to "finish" the length.  I'd like it to resonate at 3.8  
>Mhz.
>About how much pipe do I need to add to make it work. I have one of  
>Array
>Solution AS-80 tuners. I will be using about 60-80 radials about  
>60-100 feet
>long. Tha way the tuner works is it needs to resonate at 3.8 or so  
>and then
>it switches in inductance to tune it to 3.5 and 1.8.
>  Does Rohn 25 typically make a good connection between sections? I was
>thinking about running a piece pf copper wire from bottom to top secured
>with some copper-ox and circle clamps. Good idea or??  Thanks  Gregg   
>K9KL
>
>
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