Call Search
     

New to Ham Radio?
My Profile

Community
Articles
Forums
News
Reviews
Friends Remembered
Strays
Survey Question

Operating
Contesting
DX Cluster Spots
Propagation

Resources
Calendar
Classifieds
Ham Exams
Ham Links
List Archives
News Articles
Product Reviews
QSL Managers

Site Info
eHam Help (FAQ)
Support the site
The eHam Team
Advertising Info
Vision Statement
About eHam.net

   Home   Help Search  
Pages: [1]   Go Down
  Print  
Author Topic: 15' Tower Mast Raising  (Read 932 times)
KO4NX
Member

Posts: 179




Ignore
« on: January 21, 2005, 07:42:10 AM »

Hello All:


I at the point where it is almost time to install my Tashijan WT-51 crank up tower to the base I have poured. One of the questions that still remain for the install, is how to go about raising the mast through the thrust bearing once the antennas is installed on the top of the 15’ Mast section.

The only thing that I can think of at this point is to push the top portion of the mast through the thrust bearing, mount the LPDA on the one foot section I have protruding through the top of the tower, and then by hand push the mast and antenna up into the air. This method would require that I brace the mast with a piece of wood right below the thrust bearing why I work on getting the rotor plate and rotor in place. One concern with doing this is the fact that I don’t have much room inside the tower to get my hands inside to work the mast upward. This is because the tower is a crank up and all the sections are nested inside the outer section of the tower.

One suggestion given was not to use the top portion of the mast, and just stand up on the top of the tower and raise the antenna to about five feet above the thrust bearing on the tower. After some measurements this is not an option for me due to the fact it will be in the midst of some low lying trees that I have on my property.

Has anyone ever attempted to do this before, and if so are there any pointers or techniques one could relay to me that might make this process a little easier?


73

Rich Miller
AJ3G
Logged
WB2WIK
Member

Posts: 20611




Ignore
« Reply #1 on: January 21, 2005, 09:04:01 AM »

Most people do just about what you said.  

However, there is no reason to be installing a rotor in the tower while the tower is up, with the mast sticking through the thrust bearing.

Install the rotor while the tower's still horizontal, laying on the ground.  Use the crank winch to extend the tower a couple of feet, so there's more room to work, and take your time.  Once the rotor is installed, also connect the rotor cable, and route it out from the bottom of the rotor to the inside of the upper tower section leg, then route it up to the thrust bearing plate (upper plate on tower), then wrap the rotor cable 180 degrees around the tower leg so it's "outside" the tower, and tape the cable in position.  The rotor cable *must* fall outside the tower, just like the coax feedlines will, when you're all done.

If you have the space to tilt up the tower with the mast installed, then install the mast into the rotor while it's all laying on the ground, too!  (I don't have that luxury, here -- the mast will hit something on the way up.)

I don't like the idea of a 15' mast on a W-51, and usually go with 10' maximum on that type tower because the upper section isn't that strong.  (The lower two sections are *very* strong, as you can see, if you have the tower.)  For an HF LPDA antenna (6-8-10 elements, whatever you have), I wouldn't mount that more than five feet above the thrust bearing; in which case, you'll be able to reach that point by just standing on the tower webbing with the tower fully collapsed and your safety belt around the mast.

The difference in performance of an HF LPDA installed at 56' above ground or 61' above ground is inconsequential -- I don't think you'd ever notice the difference.  But the tower will be much happier with the beam at 56' (5' above the top of the tower), and so will the mast.  I wouldn't install an HF LPDA at the top of a 15' mast, on a W-51, unless it was a very temporary installation in calm weather.  In a strong windstorm, this is an accident waiting to happen.

If you like having the 15' mast, put some VHF stuff at the top of it -- smaller and lighter antennas that don't create much wind loading.

That's my 2 cents.  I've owned and installed a lot of W-51s over the years, and still have one at home.

WB2WIK/6
Logged
KO4NX
Member

Posts: 179




Ignore
« Reply #2 on: January 21, 2005, 10:26:29 AM »

Thank you very much for all the great information! The LPDA I am installing is the Tennadyne T8, which does not weigh as much as some of the LPDA's I have seen.

The Mast I am using is grade 4130 pressure tubing with .200" wall thickness. I agree that in most cases the extra 10' would not make much differnce at all in antenna performance, but my delema is that there are trees that become a factor at 56' above the ground.

I have worked it out so that by pointing the LPDA North I can crank the antenna up and without hitting any obstructions, but if I tried to rotate at 55' I will hit tree limbs in the process. This is the only reason I am tying to utilize as much of the mast as possible.

In dry warm weather the reflector elements of the T8 "droops" down almost 2' from the boom. We recently had some snow and ice in the Washington DC area and I noticed the  "drooping" to be almost 2.3' - 2.5' under those conditions. Thus I feel that I need to get the antenna to an altitude of about 60' to be in the clear.

One last question I would like to ask you since you have owned and installed this tower is, how did you get the rotor and plate in? I am looking at the top section of the tower and it does not appear as though I have enough room to get my Rotor in, but it looks to me as though it might work if I slipped the rotor in through the bottom of the tower. Again thanks for the information!

73

Rich Miller
AJ3G
Logged
WB2WIK
Member

Posts: 20611




Ignore
« Reply #3 on: January 21, 2005, 10:48:03 AM »

Depends on the rotor you have.  I have a standard HAM-IV (CDE) rotor, which fits through the webbing in the upper section just fine if you try hard enough...it takes just the right tilt angle and rotor orientation to do it, but it works.  If you have a larger rotor like a T2X, that will *not* fit.

Your tree problem sounds like it could create problems going forward.  I'd use a chain saw....seriously.

Problem is this: Let's say your tower's fully extended and the T8 is rotating happily above the trees.  Then, you have a sleet storm and now everything is coated in ice, so the beam will not turn.  Now, you have a windstorm and you really, really want to retract your tower -- but you can't, because the beam direction's stuck someplace that prohibits lowering it through the trees.  

So, you lose everything simply because there wasn't sufficient clearance to lower the beam regardless of its direction.

That's just one example.  I can think of many others.  I wouldn't want a rotating beam that can't rotate at any level I set it to, using an extendable tower.  BTW, I also have the Tennadyne, and I like it a lot.  And yes, the elements (especially that huge rear one, and maybe the second one, too) droop a lot.  I'm in L.A. so we don't get ice, but we do get birds!  A few large crows perching on that rear element can make it droop a lot more than 2-3 feet -- probably more like six feet.  The birds don't seem to mind...

73 & good luck with the installation!

Steve, WB2WIK/6
Logged
KI4CYB
Member

Posts: 47




Ignore
« Reply #4 on: January 21, 2005, 11:19:10 AM »

WB2WIK,  don't talk about bird problems!  That's a battle I am still fighting and loosing.

I feel like they laugh at me as I walk out to the car!
Maybe I am imagining things...  Smiley

73 - KI4CYB
Logged
K5LXP
Member

Posts: 4506


WWW

Ignore
« Reply #5 on: January 21, 2005, 11:32:51 AM »

I have the Tri-Ex version of your tower, and this is how I did it.

Before I put the rotor in, I brought my 12' 2" dia mast to the top of the tower and nested it almost all the way inside, (about 2' sticking out) and cinched it in place with the thrust bearing.  Then I mounted my top two antennas to the mast, a 6M ringo on the very top, and a 6M yagi about 1' from the top.  Then I pulled the mast all the way up and installed the rotator.  At that point, while lashed to the mast with a safety harness I stood on the top of the tower and installed 2M and 440 yagis on a cross boom about 5' up, then finally my Mosely tribander about 1' up.  I have since done service to the top two antennas by welding together a custom stepladder that uses pegs which fit into the ends of the tower tubing and bolts to the mast about halfway up.  It was quite sturdy and I was able to do the work without having to undo all the mid and low antennas and lowering the mast.  


Mark K5LXP
Albuquerque, NM
Logged
WA4MJF
Member

Posts: 1003




Ignore
« Reply #6 on: January 23, 2005, 12:47:10 PM »

Just outta curiousity how small is
your LPDA?  The only ones that I worked
with were when I was still in the Army.
They worked great!  However, the boom
appeared similar to Rohn 25 and the
tower like Rohn 65 and we rotated the
whole tower at the base.  

I've never had the real estate nor the money
for one of those, but a SMALLER one maybe.

73 de Ronnie

Logged
KO4NX
Member

Posts: 179




Ignore
« Reply #7 on: January 24, 2005, 06:00:49 AM »

Ronnie:

I am familiar with the LPDA you are referring too. I work with those large broadband LPDA's as a defense contractor. The LPDA that I am installing is by far much smaller. Information on this antenna can be found at www.tennadyne.com.

The model I have at my QTH is the T8 which is designed to operate from 13 – 30 MHz. Here on Eham this antenna has received some pretty great reviews. I hope this information helps.

73

Rich Miller
AJ3G
Logged
Pages: [1]   Go Up
  Print  
 
Jump to:  

Powered by MySQL Powered by PHP Powered by SMF 1.1.11 | SMF © 2006-2009, Simple Machines LLC Valid XHTML 1.0! Valid CSS!