This is a multi-part message in MIME format.
--part0_902095417_boundary
Content-ID: <0_902095417@inet_out.mail.aol.com.1>
Content-type: text/plain; charset=US-ASCII
In a message dated 98-08-02 11:16:40 EDT, owner-towertalk@contesting.com
writes:
> From: "Gary E. Jones, Ph.D." <gejones@whale.otr.usm.edu>
> Subject: Multiple antennas and Swing Arm Design
> Mime-Version: 1.0
> Content-Type: text/plain; charset="us-ascii"
>
> This comment is really a response to N4ZR and deal with his concern with so
> many yagis on one tower.
>
> Well, my QTH is 70 miles north of the Gulf of Mexico in Mississippi (part
> of Hurricane Alley). I have had a three yagi 100' stick of Rohn 45 and a
> two yagi 78' stick of Rohn 25 up through Hurricane Frederick.... sustained
> winds in Hattiesburg were in excess of 80 MPH. Lodge pole pine trees
> (60-70') were down everywhere and snapped off in the middle. All my yagis
> and towers made it through without a scratch. All yagis are heavy duty or
> stock.
>
> Now, my current Rohn 45 has the 2 element 40, over the 5 element 20, with
> the swing arm with a 5 element 15 and 5 element 20 in a 20 meter 5 over 5
> stack configuration 15M = 65" and 20M at 55') and the Th6 at about 35 feet.
> The TH6 sits at the first set of guys. It has also been through very high
> wind storms with no problems. The one hurricane we have had since this has
> been up gave us gusts into 60 - 80 MPH with narry a problem.
>
> Obviously, I try to do things right. And, the difference between Rohn 45
> and Rohn 25 is a rather substantial difference. I use Rohn guy brackets at
> all locations, and torque arms, and 1/4" EHS all around. Rohn 45 can take a
> lot more load than 25.
>
> My big swing arm (12' with 2 big yagis on it) sits right on top of the set
> of guys at 50'. The swing arm uses 2" angle iron across two faces of the
> tower, vertical legs 1 and 2 on the bottom of the arm, and vertical legs 2
> and 3 on the top of the swing arm. The arm is made of 1 1/2" schedule 40
> water pipe with a cross brace in the center (cold galvanized... wish it was
> hot dipped). I will try to draw a diagram of it below. I have never doubted
> that this tower is going to stay up... it is rock solid. The swing arms are
> twisted with HAM-IVs and there is a TB-3 thrust bearing at the top of the
> swing arm to take all the lateral torque of the swing arm and the dead
> weight of the swing arm and the antennas if the rotor needs to be replaced.
>
> My new tower will be 140' of Rohn 45 with a 5 element 15 monobander at the
> top (150'), 2 element 30/ 2 element 40 (shortened) FORCE-12 duo-band yagi
> at 140' at the top of the tower, a 12' swing arm at 70-80' with a 5 element
> 12 meter (Hygain) at 80' and a 5 element 10 meter (Hygain) at 70' and at
> 40' on a single antenna swing arm will be a 5 element 17 meter monobander
> (Hygain). My belief is that the yagis will go long before the tower is in
> trouble.
>
>
>
> Diagram of the 12' swing arm...
> ______________ Thrust Bearing (TB-3)
> -----------|| 2" angle iron
> ||______________
> |-------------|
> || // ||
> || // ||
> || // ||
> || // ||
> || // ||
> || // ||
> || // ||
> || // ||
> || // ||
> ||// ||
> ||/ || swing arm itself
> ||\\ ||
> || \\ ||
> || \\ ||
> || \\ ||
> || \\ ||
> || \\ ||
> || \\ ||
> || \\ ||
> || \\ ||
> || \\ ||
> || \\||
> ||___________\||
> ||--------------
> ||
> ||
> ||
> / \
> | | Rotor
> | |
> |___|________________ 2" angle iron
> --------------------
>
>
> That should give you a good idea of what they look like.
>
>
>
> Gary W5FI
>
>
--part0_902095417_boundary
Content-ID: <0_902095417@inet_out.mail.aol.com.2>
Content-type: message/rfc822
Content-transfer-encoding: 7bit
Content-disposition: inline
Return-Path: <owner-towertalk@contesting.com>
Received: from relay28.mx.aol.com (relay28.mail.aol.com [172.31.109.28]) by
air05.mail.aol.com (v46.20) with SMTP; Sun, 02 Aug 1998 11:16:40 2000
Received: from dayton.akorn.net (dayton.akorn.net [205.217.100.11])
by relay28.mx.aol.com (8.8.8/8.8.5/AOL-4.0.0)
with ESMTP id LAA24511 for <upthetower@aol.com>;
Sun, 2 Aug 1998 11:16:38 -0400 (EDT)
From: owner-towertalk@contesting.com
Received: (from majordom@localhost)
by dayton.akorn.net (8.8.5/8.8.5) id LAA10310;
Sun, 2 Aug 1998 11:16:38 -0400 (EDT)
To: <towertalk@contesting.com>
Date: Sun, 2 Aug 1998 11:16:38 -0400 (EDT)
Message-Id: <199808021516.LAA10310@dayton.akorn.net>
To: owner-towertalk@contesting.com
Subject: BOUNCE towertalk@contesting.com: Non-member submission from ["Gary
E. Jones, Ph.D." <gejones@whale.otr.usm.edu>]
Mime-Version: 1.0
Content-type: text/plain; charset=US-ASCII
Content-transfer-encoding: 7bit
|