[TowerTalk] Bent Sloper

[Roger (K8RI)]

Dennis Vernacchia wrote:
> Hi Roger,
>
>   About 15 years ago I put up a 72 ft motorized crank up tower on my 
> postage
> stamp sized city lot here in San Diego
>
>
> I thought I would try a 1/4 wavelength sloper antenna  that came off 
> the 72 ft level of the tower and feed at the top of the tower with 
> shield of coax connected at that top point.
This describes what I'm using on 160. Photos of how the feed is  
connected are on the bottom of  
http://www.rogerhalstead.com/ham_files/tower.htm.  It's a large page so 
might take a while to load unless you have a fast connection.

The antenna loaded well the first try but I shortened it about  a foot 
to make it easier to tune across the whole band. Before shortening the 
tuner would arc inside when running the legal limit near the top of the 
band.  It's basically a 1/4 wave with a large array directly above the 
feed point.
>
> The lot is 50 feet wide ( East West direction ) and approx 110 ft long 
> ( North South Direction )and tower is located in center of 25 ft width 
> and about 40 ft from the back-  South end of lot.
>
> I strung the sloper out to a pole in the NE corner of my lot hoping 
> most of the RF would
> radiate to the NE direction which would be very desired being in the 
> extreme SW
> corner of the U.S.
>
> Well, the antenna acted as if it was very short and resonated above 
> the 160 band.
>
> Well the antenna resonated up WAY above 2 mHz so I started adding wire 
> and since I was out of room
> going in the NE direction, I brought the excess wire from the NE pole 
> to another pole
> at the SW corner of my lot about 15 ft above the ground and still 
> showed too short
> so I added a 25 foot section that dog legged from SW corner toward the 
> center of my lot to the east.
>
I'm thinking more of dropping the feed line vertically from the feed 
point with the bottom half of  the antenna being horizontal between 50 
and 60 feet above ground. The feed line will then curve back to the 
tower well below the horizontal section of the dipole.
> Anyway, this design seems to approximate the configuration you were 
> asking about.
>
Good luck on the  noise problem.

73

Roger (K8RI)
> How does it work? Well, I have been copied in Moscow and New Zealand, 
> South America and Japan
>
> Unfortunately I have a diode mix on or near my property that renders 
> this wonderful city lot Transmit antenna
> USELESS on RECEIVE because of AM Broadcast Mix interference that is 50 
> dB over S9 on many freqs
> in the 1.8 to 2 mHz band. ( I use a 6 FT Loop with Low noise pre-amp 
> to receive on allowing me
> to hear most but not all DX stns that can hear me.
>
> John K6AM and I continue to work on finding the source of the AM BCI 
> mix interference but hopefully
> this story gives a clue where the heck it radiates.
>
> Also. John K6AM modeled the antenna with EZNEC Wires and it says the 
> antenna doesn't work....go figure.
> As Emily Latella of SNL fame would say......."Now isn't RF just 
> WONDERFUL !"
>
> 73, Dennis N6KI
>