TopBand: Re: problem with half sloper for 160 meters

[Ryszard Tymkiewicz]

At 10:23 PM 2/2/98 -0500, you wrote:
>Timon,
>   I have almost excatly the same situation. Using four 80 meter slopers
>attatched to the 60 foot level of my 74 foot Rohn 25G tower, I've worked
>306 countries on 80 in the past 5 years. However this antenna will not work
>on 160 Meters if I double the length of the wire. Indeed it resonates no
>lower that 2.0 Mhz. After several years of trying to duplicate my system on
>160 I've had little success. I suspect the attatchment point is critical to
>the half sloper antenna. Also I reason the height, and antenna compliment
>of the support strcture to be a critical factor in the half sloper. I have
>2 friends that use the half sloper very successfully on 160 meters. These
>antennas are attached to the 35-38 foot level on self supporting Rohn HDBX
>48' towers. The antenna is very mysterious even to experts like ON4UN. He
>makes a very brief explination of this antenna in his famous low band dxing
>book. However I doubt anyone really understands the mechanics of the
>antenna. Perhaps L.B. or some of the antenna guru's can explain the elusive
>nature of why this antenna either smokes or flops. Believe me I've had both
>versions. I am beginning to believe the secret of this antenna is to find
>the 50 ohm point on your support tower for the frequency desired. This of
>course is the 64 dollar question, HOW? The support structure seems to have
>an almost infinate number of variables, and I assume, finding the correct
>attatchment point seems to be the answer. I wonder if a rule of thumb could
>be confirmed; that the lower the frequency the lower the attatchment point?
>This is only a theory, but it seems to work in some cases. I hope we can
>get a meaningful discussion of the half sloper started, cause I've
>expermented with them for years, and the only thing I know for sure is,
>when they work they are super, and when they don't, forget it and try
>another kind of antenna.
>
>Sincerely,
>
>Mick  W4YV 
>
>



 I had the same situation.I'm using 18m high tower with TH6DXX and A3WS on
the top.
 I was not able to tune my half sloper on 160m using only one "arm" of the
antenna.
Anyway ,I added shorter wire /about 30m long/ connected directly to the
tower on the top /without any insulator-just as a "cold" one/ with the angle
about 150 deg to the "hot" one. I obtained SWR 1:1.2 with a quite narrow
band /what seems to be good/ 
1820-1850 kHz. The resonant frequency depends very much of lenght of "cold"
wire and a angle between arms.
Well, its not too high /18m/ but I worked on it 240 countries.


                      73 Rys SP5EWY


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