[TowerTalk] Half slopers using a tower

[Bill Coleman]

On 1/1/02 6:48 PM, Stephanie WX3K at wx3k@ptd.net wrote:

>
>-----Original Message-----
>From: Bill Coleman [mailto:aa4lr@arrl.net]
>Sent: Tuesday, January 01, 2002 5:52 PM
>To: Stephanie WX3K; Towertalk
>Subject: Re: [TowerTalk] Half slopers using a tower
>
>
>On 12/31/01 4:59 PM, Stephanie WX3K at wx3k@ptd.net wrote:
>
>>My tower is 65 feet with a Mosley Pro95 beam sitting just above the thrust
>>bearing. The "Half-Sloper" is hung at a 45 degree down at the 50 foot
>>level.....about 128 feet of wire...fed at the 50 foot level with 50 ohm
>coax
>>and the shield ground right there on the tower.
>
>Somehow the math doesn't work out. 45 degrees at 50 feet should require
>about 90 feetof wire. For 128 feet, it must be shallower than 45 derees.
>
>>>>>Please share your calculations !!!!!

I assume your tower is set in flat ground. Thus, the tower, the antenna 
wire, and the ground make a large triangle. Since the angles of a 
triangle must sum up to 180 degrees, we have a 90 degree angle at the 
tower, 45 from the tower to the sloper, which leaves 45 degrees from the 
sloper to the ground. Such a triangle must have equal sides, which are 
declared as 50 feet. The sloper, therefore, must be have a length of one 
side times root 2. This is roughly 1.4.

1.4 * 50 = 90 feet. (oops -- did the math wrong the first time)

1.4 * 50 = 70 feet. (Yup, that's right)

>>Anyone ever try this ??? The
>>match I have is still unacceptable...2.5 to 1.....Any suggestions ?
>
>What band? 40m? 80m? 160m? It seems too long for either 40m or 80m, and
>too short for 160m.
>
>>>>>An earlier email mentioned 160 meters

Ah, that may be a problem. You probably don't have enough tower to 
properly act as the other half of the sloper.

I'd suggest an Inverted L instead.



Bill Coleman, AA4LR, PP-ASEL        Mail: aa4lr@arrl.net
Quote: "Not within a thousand years will man ever fly!"
            -- Wilbur Wright, 1901


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