[TowerTalk] Half Sloper recommendations - Results!

[Roger (K8RI)]

RLVZ at aol.com wrote:
> Hi Guys,
>  
> Happy New Year!
>  
> Thank You to 10 people who replied concerning my questions about  
> installing a 160-meter "Half Sloper" or moving my Inv. L from my 90' tower  (where it 
> works poorly) over to my 60' tower.  Your comments  are much appreciated 
> and gave good direction!  My original post  is shown below in case anyone 
> missed it and wonder what I'm talking  about.  
>  
> Basically, I had two questions:
>  
> 1) Should I install a Half Sloper on my 90' tower and if so how could I do  
> so and maximize radiation efficiency?    
>  
> 2) Since my Inv. L works poorly on my 90' tower due to  heavy tower 
> interaction... should I move this Inv. L to my 60' tower  rather than use the 
> Sloper at 90'?
>  
> RESULTS OF THE 10 REPLIES:
>  
> -1 VOTE TO INSTALL SLOPER ON THE 90' TOWER BUT "BE SURE TO USE  RADIALS".
>   
I have a half sloper on my 100' 45G. It  comes off very close to the 
top. http://www.rogerhalstead.com/ham_files/Tower30.htm Although 
invisible in the photo it comes off the tower about 3' below the 
tribander and anchors about 50' to the right of where I shot the photo.  
It's of #14 copper weld and does not sag as it's under a lot of 
tension.  The angle is close to 45 degrees. There's lots of *stuff* 
mounted on the tower, not all of which shows in the photo. There are 
presently 2 center fed, half wave slopers on  40 and two on 74.

It seems to have worked well and although I use no radials, there is an 
elaborate grounding system consisting of 32 or 33 8' ground rods, 
Cadwelded (TM) to well over 600 feet of bare #2 copper just under the 
surface. I doubt it does much in the way of serving as radials.

The 160 half sloper is not being used at present, but next time "up 
there" I need to haul a feed line back up so I can get on "top band" again.

BTW a bit over 3/4 of the way down 
http://www.rogerhalstead.com/ham_files/tower.htm are photos of the 
antenna mounting and feed line details.

73

Roger (K8RI)
>  
> -2 VOTES TO INSTALL INV. L ON THE 60' TOWER AND IT WILL DO BETTER THAN THE  
> 90' TOWER DUE TO LESS TOWER INTERACTION.
>  
> -2 VOTES TO INSTALL AN INVERTED VEE ON THE 90' TOWER.  (INTERESTING AS  I 
> DIDN'T LIST AN INV VEE IN THE OPTIONS.  I HAVE USED INV.
>     VEES AT THIS LOCATION FOR YEARS AND THEY WORK PRETTY  WELL IN THAT I 
> CAN USUALLY WORK EVERYONE I CAN HEAR)
>  
> -5 VOTES TO "SHUNT FEED" THE 90' TOWER.  (VERY INTERESTING AS I DIDN'T  
> LIST "SHUNT FEED" AS ONE OF MY OPTIONS!)
>  
> CONCLUSION:
>  
> Since 5 out of 10 responders said I should "Shunt Feed the 90' tower it's  
> clear direction that my next project will be to "Shunt Feed the 90' tower.   
> What really cinched it is that I didn't include "Shunt Feed" in the 2  
> options I was considering and yet it got the most votes!  So for those who  are 
> interested in improving their 160-m. performance like me... you might want  
> to try "Shunt Feeding" one of your towers.
>  
> Shunt Tower Feed Questions:
>  
> 1) My 90' tower is a self-supporting aluminum tower with a top mounted  
> Tribander.  (no guy wires)  The five responders who said I should  "Shunt Feed 
> that 90' tower" recommended I attach the shunt at various  heights ranging 
> from 30' to 90' up on the tower and adjust as needed.   QUESTION 1: Will 
> using a different attachment height and wire spacing  only effect the loading 
> and bandwidth or is there an attachment height that  will provide better 
> radiating efficiency?  
>  
> 2) I'd like to try a "Slant Feed" as many old AM Broadcast  towers use.  
> For one thing, it would make installation quicker and with  less climbing as 
> it wouldn't need PVC insulators keeping  the shunt wire equally spaced.  
> QUESTION 2: Is the "Slant Feed" likely  to tune and radiate about the same as a 
> common 'Shunt Feed" with equally  spaced wire parallel to the tower?  
> QUESTION 3: Is there any general  rule of thumb for where to attach a "Slant Feed" 
> on a 1/4 wavelength  tower?  Such as, 25% up the tower above ground level?  
> (I've  seen a couple 1/4 wave AM Broadcast towers and it seemed like  the 
> Slant Feed wires were connected about 25% of the way up the tower  from 
> ground... so perhaps aprx. 25% is the general rule of thumb?)  
>  
> Thanks again guys... you're a wonderful help!  
>  
> 73,
> Dick- K9OM
>  
>  
>  
>  
> Hi Guys-
>
> I'd appreciate your recommendations on building a Half  Sloper for  160-m.  
> I realize that some folk have had excellent  results with Half  Slopers and 
> others have had terrible results with  them!  That's why I'm  asking for 
> advise on how to construct my  Half Sloper!
>
> Question 1: Most antenna articles say when constructing an  Inv. Vee is  to 
> keep the minimum angle between wires at 90 degrees or  greater.  Since  
> Half 
> Slopers almost never have a 90 degree angle  between the sloper wire and 
> the  
> tower is this one reason why many Half  Slopers don't work very well... 
> lots 
> of signal cancellation?
>
> Question  2: I have a 90' tower with a Tribander on top which makes it very 
>   
> close to a 1/4 wave for 160-m.  I installed an Inverted L on this   tower 
> with 85' vertical and the Inv. L radiating efficiency is very   poor due to 
> heavy coupling between the Inverted L and the  tower.   (some models say 
> that 
> alot of RF is shorted right to  ground!)   Therefore, I am thinking of 
> going 
> with a Half Sloper  connected near  the top of the 90' tower with the 
> sloper 
> wire running  NE towards  Europe.  If I anchor the end of the sloper wire 
> about 
> 200' from   the tower the angle is only going to be about 45 degrees.  Do 
> you  think  this will work any better towards Europe than my heavily 
> coupled  
> and inefficient  Inv. L?  (another weakness with my Inv. L is that  I have 
> a 
> minimal  radial system as it must be pulled up each  Spring).
>
> Question 3: Rather than build the Half Sloper on the 90'  tower  would an 
> Inv. L on my 60' tower with 55' vertical and the rest  horizontal  running 
> NE 
> towards Europe likely outperform the Half Sloper  at 90' towards  Europe... 
> keeping in mind that this is a temporary  antenna so I can only  put down a 
> minimal radial system as the radials  need to be removed  in Spring.  
>
> I realize that I'm likely to  get a variety of opinions on this and that is 
>  
> fine!  Please let  me know which of the above options you believe  is most 
> likely to  provide the best 160-m. signal towards Europe.
>
> Happy New  Year!
>
> 73,
> Dick- K9OM
> Edgewater,  Florida
>
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