This was a subject I presented a few months ago with great response here on
the reflector and privately. My L is about 70' vertical and 62' horizontal,
fed with LMR 400 through a 2:1 unun, 1 ground rod approx. 5' feet into the
hardest ground you will find east of the Mississippi. I started out with 4
radials, wasn't bad, about 1.5 at 1850, check the MFJ and the z was wacky, so
after
getting some tips, I started adding radials, everytime I added a radial I
check the vsr , it was going up and my z was going down. Total radials up to
date, 24 @ 133'. I did add more, but nothing changed so I left it at 24
radials. At 1800 1.6 at 1850 1.4 and at 1900 1.7. This ant plays very well,
everything I hear on the receive loops, I can work and its been a blast to be
back
on 160. Enjoy the DX chase on this band its a challenge but a lot of great fun
John
ND1X.
In a message dated 12/4/2008 11:19:37 P.M. Eastern Standard Time,
towertalk-request@contesting.com writes:
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Today's Topics:
1. Re: 2000 Foot Tower, Antenna Replacement (Michael Germino)
2. Re: Climbing and working on Rohn 25g/45g towers - (Roger (K8RI))
3. Tower Disaster (Mark Robinson)
4. Inverted L Tuning Question (RLVZ@aol.com)
5. Re: Inverted L Tuning Question (Richards)
6. Re: Inverted L Tuning Question (Tom Osborne)
7. Re: Inverted L Tuning Question (Dennis Vernacchia)
8. Re: Inverted L Tuning Question (K2EK@aol.com)
9. Inverted L Tuning - Solved (RLVZ@aol.com)
10. Re: Inverted L Tuning - Solved (Richards)
11. Re: Inverted L Tuning Question (RICHARD SOLOMON)
----------------------------------------------------------------------
Message: 1
Date: Wed, 3 Dec 2008 21:14:53 -0800 (PST)
From: Michael Germino <ad6aa@sbcglobal.net>
Subject: Re: [TowerTalk] 2000 Foot Tower, Antenna Replacement
To: Tower Talk <towertalk@contesting.com>
Message-ID: <842607.56021.qm@web82403.mail.mud.yahoo.com>
Content-Type: text/plain; charset=us-ascii
I liked the watermelon they threw off of the tower.
Mike
------------------------------
Message: 2
Date: Thu, 04 Dec 2008 16:41:14 -0500
From: "Roger (K8RI)" <K8RI-on-TowerTalk@tm.net>
Subject: Re: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
Cc: towertalk@contesting.com
Message-ID: <49384E7A.1000507@tm.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Bill Aycock wrote:
> I have a real problem with this. I have asked for a description of the way
a
> force is applied to the tower, and how the tower section is mounted, to
show
>
Shear strength is perpendicular to the tower (or brace) and even if we
know how it was measured it doesn't give us a lot of information as a
load is seldom applied in a direct shear mode. (It would be if tied to a
horizontal brace.) There is almost always some bending moment. I think
it was mentioned earlier that shear is in the weakest direction. It also
has very little to do with normal antenna loading unless the antenna is
located right at a guy point, or as in the case of a TIC Ring. Maximum
antenna wind load is a small fraction of the shear strength.
What scares me is watching some one climb one of the Aluminum towers
while bending the braces from their weight.
I wouldn't call it silly, but I agree, "shear strength" in most cases
tells us little in the practical sense.
73
Roger (K8RI)
> how this "strength" is defined. So far I have no luck.
> Tossing phrases like "Shear Strength" around without knowing what they
mean
> is silly.
> Bill--W4BSG
>
> ----- Original Message -----
> From: "Bill Coleman" <aa4lr@arrl.net>
> To: "Richard Elizondo" <relizondo@ionoscom.com>
> Cc: <towertalk@contesting.com>
> Sent: Thursday, December 04, 2008 7:07 AM
> Subject: Re: [TowerTalk] Climbing and working on Rohn 25g/45g towers -
>
>
>
>> On Nov 23, 2008, at 11:43 PM, Richard Elizondo wrote:
>>
>>
>>> Here is the shocking sad truth:
>>>
>>> Rohn 25g section shearing strength - 2500lbs (this is the strength
>>> of the
>>> entire section, all three legs and lattice, not just that one leg
>>> you may be
>>> attaching to.
>>>
>>> So a Rohn 25g section could fail if a climber falls and the lanyard
>>> shock
>>> pack does not activate, or the climber is using a lanyard without a
>>> shock
>>> pack.
>>>
>>> Sadly enough the Rohn 45g section is not that much stronger.
>>>
>> However, in a fall arrest situation, it is unlikely that all of the
>> arrest force occurs in the shear direction. 25G has considerably more
>> vertical support strength. On a 200 foot 25G tower, the static load on
>> the base likely exceeds 2500 lbs to start.
>>
>>
>>> Solutions for the Climber:
>>>
>>> First and foremost - Never attach to the Z lattice of these towers
>>> for any
>>> reason.
>>>
>> If a single weld fails, then the Z bracing will deform -- that
>> deformation will absorb some of the fall energy. The remaining energy
>> will be directed at the remaining upper and lower welds. It seems
>> unlikely that a 6 foot fall would create so much energy as to undo
>> every weld on a section.
>>
>> It does seem seriously unwise to attach to the top or bottom "flat"
>> part of the bracing. There, a single weld failure would likely allow
>> the fall arrest lanyard to detach from the tower entirely.
>>
>> Bill Coleman, AA4LR, PP-ASEL Mail: aa4lr@arrl.net
>> Quote: "Not within a thousand years will man ever fly!"
>> -- Wilbur Wright, 1901
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
------------------------------
Message: 3
Date: Thu, 4 Dec 2008 16:53:06 -0500
From: "Mark Robinson" <markrob@mindspring.com>
Subject: [TowerTalk] Tower Disaster
To: <towertalk@contesting.com>
Message-ID: <06a301c9565a$b1717d20$6600a8c0@hplaptop>
Content-Type: text/plain; format=flowed; charset="iso-8859-1";
reply-type=original
This a tragic story and it shows how quickly things can go wrong.
http://www.sbe36.org/1999/0212.html
Mark N1UK
------------------------------
Message: 4
Date: Thu, 4 Dec 2008 18:06:16 EST
From: RLVZ@aol.com
Subject: [TowerTalk] Inverted L Tuning Question
To: topband@contesting.com, towertalk@contesting.com
Message-ID: <ccc.4559e55e.3669bc68@aol.com>
Content-Type: text/plain; charset="US-ASCII"
Hi Guys,
I'm trying to set up a 160-m. Inverted L for ARRL-160 this weekend but am
having an interesting tuning problem. All thoughts appreciated!
The Inverted L is made up of #12 stranded copper wire 136' in total length:
82' vertical and 54' horizontal. The vertical wire is spaced 6' from a 88'
self-supporting tower with a Cushcraft XM-240 mounted on top. (XM-240
elements
are not grounded) Initial radial system is 2- 135' radials laying on the
ground- not much but two similar radials worked pretty well on my 60' tower
last
year as the towers are 150' from a salt water river.
Placing the Antenna Analyzer (AIM 4170) at the base of the Inverted L gets
the following measurements:
1) With the coax braid connected to the tower base which has two 8' ground
rods: lowest SWR is 3.9 at 1.776 Mhz and Z = 79.
2) With coax braid only connected to the two radials (and not the tower
base): lowest SWR is 1.62 at 1.614 Mhz and Z = 81.
It was my understanding that the coax braid should be connected to both the
radials and the base of the towers gnd system, but as you can see the the
minimum SWR and resonant freq. go crazy when I do.
Any recommendations what I can do to get it working before tmw night?
73,
Dick- K9OM
**************
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and favorite sites in one place. Try it now.
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------------------------------
Message: 5
Date: Thu, 04 Dec 2008 18:57:27 -0500
From: Richards <jruing@ameritech.net>
Subject: Re: [TowerTalk] Inverted L Tuning Question
To: RLVZ@aol.com
Cc: towertalk@contesting.com, topband@contesting.com
Message-ID: <49386E67.9070301@ameritech.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
I would not connect it to the tower, itself. If the tower is connected to
the ground rods, then I would just use radial wires laying on the ground.
I would lay more ground wires if using just those. In other words, I
would not include the tower, per se, in my counterpoise system.
Your situation brings some humor to mind:
Doctor asks = Does it hurt?
Patient says = Only when I do this (gesturing.)
Doctor says = Well... don't do this.
If connecting to tower is worse than using radials alone..... then
don't do this. .... ;-)
But seriously folks...
I am sending some good research materials on L antennas to you under
separate cover. Hope they are useful
Just MY take... Good luck. //// Richards - K8JHR ////
======================================================
RLVZ@aol.com wrote:
>
> 1) With the coax braid connected to the tower base which has two 8' ground
> rods: lowest SWR is 3.9 at 1.776 Mhz and Z = 79.
>
> 2) With coax braid only connected to the two radials (and not the tower
> base): lowest SWR is 1.62 at 1.614 Mhz and Z = 81.
>
===========================================================
------------------------------
Message: 6
Date: Thu, 04 Dec 2008 18:09:12 -0800
From: "Tom Osborne" <w7why@verizon.net>
Subject: Re: [TowerTalk] Inverted L Tuning Question
To: "Towertalk" <towertalk@contesting.com>
Message-ID: <0E4016C6EA6B46FF8B84B79D5E8E4840@Tom>
Content-Type: text/plain; format=flowed; charset=iso-8859-1;
reply-type=original
Hi Dick
You can get some screwy readings if there is a BC station nearby. I can't
even use my analyzer here on my 160 inverted L because of RF from the local.
I have to use the SWR bridge in the shack. 73
Tom W7WHy
> Hi Guys,
>
> I'm trying to set up a 160-m. Inverted L for ARRL-160 this weekend but am
> having an interesting tuning problem. All thoughts appreciated!
>
> The Inverted L is made up of #12 stranded copper wire 136' in total
> length:
> 82' vertical and 54' horizontal. The vertical wire is spaced 6' from a
> 88'
> self-supporting tower with a Cushcraft XM-240 mounted on top. (XM-240
> elements
> are not grounded) Initial radial system is 2- 135' radials laying on
> the
> ground- not much but two similar radials worked pretty well on my 60'
> tower last
> year as the towers are 150' from a salt water river.
>
> Placing the Antenna Analyzer (AIM 4170) at the base of the Inverted L gets
> the following measurements:
>
> 1) With the coax braid connected to the tower base which has two 8' ground
> rods: lowest SWR is 3.9 at 1.776 Mhz and Z = 79.
>
> 2) With coax braid only connected to the two radials (and not the tower
> base): lowest SWR is 1.62 at 1.614 Mhz and Z = 81.
>
> It was my understanding that the coax braid should be connected to both
> the
> radials and the base of the towers gnd system, but as you can see the the
> minimum SWR and resonant freq. go crazy when I do.
>
> Any recommendations what I can do to get it working before tmw night?
>
> 73,
> Dick- K9OM
------------------------------
Message: 7
Date: Thu, 4 Dec 2008 18:22:55 -0800
From: "Dennis Vernacchia" <n6ki73@gmail.com>
Subject: Re: [TowerTalk] Inverted L Tuning Question
To: "Tom Osborne" <w7why@verizon.net>
Cc: Towertalk <towertalk@contesting.com>
Message-ID:
<265781b30812041822k64364bb0g4171954c4d0ee774@mail.gmail.com>
Content-Type: text/plain; charset=ISO-8859-1
The issue with teh AM BC Strong Signal interference is addressed in
the Nov/DEC NCJ
( National Contest Journal ) magazine article
..and article uses exact same antenna analyzer as Dick is using !
73, Dennsi N6KI
On Thu, Dec 4, 2008 at 6:09 PM, Tom Osborne <w7why@verizon.net> wrote:
> Hi Dick
>
> You can get some screwy readings if there is a BC station nearby. I can't
> even use my analyzer here on my 160 inverted L because of RF from the
> local.
> I have to use the SWR bridge in the shack. 73
> Tom W7WHy
>
>
>
> > Hi Guys,
> >
> > I'm trying to set up a 160-m. Inverted L for ARRL-160 this weekend but am
> > having an interesting tuning problem. All thoughts appreciated!
> >
> > The Inverted L is made up of #12 stranded copper wire 136' in total
> > length:
> > 82' vertical and 54' horizontal. The vertical wire is spaced 6' from a
> > 88'
> > self-supporting tower with a Cushcraft XM-240 mounted on top. (XM-240
> > elements
> > are not grounded) Initial radial system is 2- 135' radials laying on
> > the
> > ground- not much but two similar radials worked pretty well on my 60'
> > tower last
> > year as the towers are 150' from a salt water river.
> >
> > Placing the Antenna Analyzer (AIM 4170) at the base of the Inverted L
> gets
> > the following measurements:
> >
> > 1) With the coax braid connected to the tower base which has two 8'
> ground
> > rods: lowest SWR is 3.9 at 1.776 Mhz and Z = 79.
> >
> > 2) With coax braid only connected to the two radials (and not the tower
> > base): lowest SWR is 1.62 at 1.614 Mhz and Z = 81.
> >
> > It was my understanding that the coax braid should be connected to both
> > the
> > radials and the base of the towers gnd system, but as you can see the the
> > minimum SWR and resonant freq. go crazy when I do.
> >
> > Any recommendations what I can do to get it working before tmw night?
> >
> > 73,
> > Dick- K9OM
>
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
------------------------------
Message: 8
Date: Thu, 4 Dec 2008 21:36:44 EST
From: K2EK@aol.com
Subject: Re: [TowerTalk] Inverted L Tuning Question
To: towertalk@contesting.com
Message-ID: <c40.4c6ee701.3669edbc@aol.com>
Content-Type: text/plain; charset="US-ASCII"
Rick
My inv-L is 60' vertical plus 75' +/- sloping down and away from the tower
(70' topped with an X7). There is 6' separation between the tower and
vertical
wire. I also use the tower as a folded monopole on 80. Consequently it is
tied to the radials (100 x 65').
I found I needed to use a series cap between the coax and vertical wire. I
think I wound up with 2 or 300pf. You could try a 2 section BC variable to
get
an idea. In my case, the horizontal wire started out at almost 85'. I had
to
go back and forth between trimming that and tuning the cap. Eventually I
had
a very nice match at 1835. If this works for you, you can then improvise a
HV
cap by using 12" pieces of scrap RG8. Each piece will contribute about 28 -
30pf (make sure you maintain 1/2" or so separation between braids and center
conductors).
I used an MFJ269 at the base for tuning. It was oblivious to a 10Kw BC
station 5 or 6 miles north of me.
73 and GL
Bill
K2EK
**************Make your life easier with all your friends, email, and
favorite sites in one place. Try it now.
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0)
------------------------------
Message: 9
Date: Thu, 4 Dec 2008 22:29:49 EST
From: RLVZ@aol.com
Subject: [TowerTalk] Inverted L Tuning - Solved
To: topband@contesting.com, towertalk@contesting.com
Message-ID: <c81.4066087a.3669fa2d@aol.com>
Content-Type: text/plain; charset="US-ASCII"
Hi Guys,
Thank You for all the wonderful ideas on getting my 160-m. Inverted L tuned.
Your ideas got me going!
My first mistake was connecting the radial ground to my tower ground.
Here's
what fixed the Inverted L:
1) Disconnected the tower ground from the radial ground and the SWR improved.
2) Put in a new 10' ground rod at the base of the Inverted L and tied it
into
the radial ground and the SWR dropped further to 1.8 @ 1.77 Mhz @ Z=28.
3) Now that the Z was down where it should be I added the 50/25 ohm UNUN and
presto: SWR is 1.06 @ 1.761 Mhz.
Tomorrow I plan to cut the top of the L a little shorter for resonance at
1.830.
Hope to work you in the ARRL-160 Test this weekend!
73,
Dick- K9OM
**************
Make your life easier with all your friends, email,
and favorite sites in one place. Try it now.
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icid=aolcom40vanity&ncid=emlcntaolcom00000010)
------------------------------
Message: 10
Date: Thu, 04 Dec 2008 22:33:21 -0500
From: Richards <jruing@ameritech.net>
Subject: Re: [TowerTalk] Inverted L Tuning - Solved
To: RLVZ@aol.com
Cc: towertalk@contesting.com, topband@contesting.com
Message-ID: <4938A101.3070507@ameritech.net>
Content-Type: text/plain; charset=ISO-8859-1; format=flowed
Great - Glad to help -- You might try a few extra radials, also, as I
believe that will bring the SWR down naturally. It does for my vertical
monopole.
Happy trails. ======== Richards - K8JHR =============
RLVZ@aol.com wrote:
> 3) Now that the Z was down where it should be I added the 50/25 ohm
UNUN and
> presto: SWR is 1.06 @ 1.761 Mhz.
>
> Tomorrow I plan to cut the top of the L a little shorter for resonance at
> 1.830.
=====================================================
------------------------------
Message: 11
Date: Fri, 5 Dec 2008 04:18:50 +0000
From: RICHARD SOLOMON <w1ksz@q.com>
Subject: Re: [TowerTalk] Inverted L Tuning Question
To: TowerTalk <towertalk@contesting.com>
Message-ID: <BAY130-W14097877AA81547E771715E0FE0@phx.gbl>
Content-Type: text/plain; charset="iso-8859-1"
Is that article available on line ?
Thanks, Dick, W1KSZ> Date: Thu, 4 Dec 2008 18:22:55 -0800> From:
n6ki73@gmail.com> To: w7why@verizon.net> CC: towertalk@contesting.com>
Subject: Re:
[TowerTalk] Inverted L Tuning Question> > The issue with teh AM BC Strong
Signal
interference is addressed in> the Nov/DEC NCJ> ( National Contest Journal )
magazine article> ..and article uses exact same antenna analyzer as Dick is
using !> 73, Dennsi N6KI> > On Thu, Dec 4, 2008 at 6:09 PM, Tom Osborne
<w7why@verizon.net> wrote:> > > Hi Dick> >> > You can get some screwy readings
if
there is a BC station nearby. I can't> > even use my analyzer here on my 160
inverted L because of RF from the> > local.> > I have to use the SWR bridge in
the shack. 73> > Tom W7WHy> >> >> >> > > Hi Guys,> > >> > > I'm trying to
set up a 160-m. Inverted L for ARRL-160 this weekend but am&> > > having an
interesting tuning problem. All thoughts appreciated!> > >> > > The Inverted L
is made up of #12 stranded copper wire 136' in total> > > length:> > >
82' vertical and 54' horizontal. The vertical wire is spaced 6' from a> > >
88'> > > self-supporting tower with a Cushcraft XM-240 mounted on top.
(XM-240> > > elements> > > are not grounded) Initial radial system is 2- 135'
radials laying on> > > the> > > ground- not much but two similar radials
worked
pretty well on my 60'> > > tower last> > > year as the towers are 150' from a
salt water river.> > >> > > Placing the Antenna Analyzer (AIM 4170) at the
base of the Inverted L> > gets> > > the following measurements:> > >> > > 1)
With the coax braid connected to the tower base which has two 8'> > ground> >
>
rods: lowest SWR is 3.9 at 1.776 Mhz and Z = 79.> > >> > > 2) With coax
braid only connected to the two radials (and not the tower> > > base): lowest
SWR is 1.62 at 1.614 Mhz and Z = 81.> > >> > > It was my understanding that
the
coax braid should be connected to both> > > the> > > radials and the base of
the towers gnd system, but as you can see the the> > > minimum SWR
and resonant freq. go crazy when I do.> > >> > > Any recommendations what I
can do to get it working before tmw night?> > >> > > 73,> > > Dick- K9OM> >>
> _______________________________________________> >> >> >> >
_______________________________________________> > TowerTalk mailing list> >
TowerTalk@contesting.com> >
http://lists.contesting.com/mailman/listinfo/towertalk> >>
_______________________________________________> > > >
_______________________________________________> TowerTalk mailing list>
TowerTalk@contesting.com>
http://lists.contesting.com/mailman/listinfo/towertalk
------------------------------
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End of TowerTalk Digest, Vol 72, Issue 10
*****************************************
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