RLVZ@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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>
>
>
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