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Author Topic: Tower/Antenna Questions (new to towers and beams  (Read 697 times)
K4KMG
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Posts: 16




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« on: September 10, 2002, 08:56:08 PM »

I recently acquired a 40' Aluma crank up/foldover tower, 7' of 6061 1.5" tubing, Ham IV rotor, and a CD 45 II. My plans are to put a Cushcraft MA5B atop this setup. The tower is up and grounded. This is my first tower/beam setup, so a number of questions come to mind.

1. Do I need to use a thrust bearing for the tubing, or will a bushing/sleeve do the job? The MA5B weighs 26.5 pounds.

2. Is it neccessary to have elavation control as well as rotation or is just rotation sufficient for this beam?

3. Best place to get cable/connectors for the HamIV, and what is the best cable to use?

4. Is it possible to interface the CD-45 to my computer? If so, how and with what?

Thanks in advance.

73
Tom Foglesong
K4KMG


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K6RAS
Member

Posts: 78




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« Reply #1 on: September 11, 2002, 12:01:19 AM »

The only point I can respond to in your list of questions is whether to use a thrust bearing or bushing.  I'd never use a bushing on my beams.  I always use thrust bearings for their benefit in reducing the axial loads.  Using a thrust bearing will help your rotor last much much longer.
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WB2WIK
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Posts: 20547




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« Reply #2 on: September 11, 2002, 12:30:37 PM »

Not sure why you have two rotors for one beam.  Neither the HAM-IV nor the CD-45 can be used for elevation.  The MA5B can be easily rotated by the CD-45, so unless you have other plans, I'd sell the HAM-IV.

I always use a thrust bearing, on general principle, but must admit that a single MA5B atop 7' of mast, with the rotor mounted on a plate inside the tower, creates such light stress on the rotor, that a thrust bearing definitely is not necessary.  Just be sure you have the rotor aligned precisely (in position) under the mast as it rotates to prevent rotor torque imbalance which will quickly wear the rotor bearings and trash the rotor.  This is easily accomplished by proper positioning of the rotor and its plate, and drilling new holes in the plate if necessary to achieve perfect vertical alignment.

There's no reason to elevation control an HF beam.

Cable for the HAM-IV or CD-45 (they both use the same 8-conductor cable) is available from dozens of amateur radio supply outlets and cable distributors.  I like Belden 8448, but I also like the 8-conductor "heavy duty" rotor cables sold by Cable XPerts, The RF Connection and many other specialty cable distributors who advertise extensively in the ham magazines, and some advertise right here on eHam.net.

The CD-45 or HAM-IV normally has no "connector" at all, just an 8-screw terminal strip, unless you have a very new one.  If you have a very new one, it should have come with the mating connector.  If for some reason you simply don't have it and need one, they are available inexpensively from C.A.T.S. "The Rotor Doctor" and "Norm's Rotor Service" via mail order, in about 2 days.  Both these businesses have websites.

You can interface the CD-45 or HAM-IV to a computer, but you need a hardware interface, not just software.  It's expensive, but available commercially.  Plans for homebrewing such an interface ("smart rotor control") have been published in QST and are available as reprints from the ARRL.  If you'd like the specifics on those two matters, e-mail me, and I'll provide them after doing some lookups.

WB2WIK/6

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K4KMG
Member

Posts: 16




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« Reply #3 on: September 11, 2002, 03:19:27 PM »

Thanks for the great replies.

Steve, the cd45 is the control box for the ham4. I'm assuming I can make the thrust bearing from something I get from my local Miller Bearing store, or are these commercially available? I do have every tool known to mankind, (at least the xyl thinks so), so I figure this should not be to hard to work out.
Thanks again,
Tom
K4KMG
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KL7IPV
Member

Posts: 984




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« Reply #4 on: September 12, 2002, 01:42:51 AM »

I have been using a Ham IV for 19 years without a thrust bearing. I used one in Anchorage for 12 years without a thrust bearing. Here I am using the same configuration: an Explorer 14 triband beam, a 6 meter vertical, a 2 meter J-pole and a 5L 2 meter beam. I tore the rotator apart when I moved here after using it for 16 years and there was no wear inside the rotator. I just regreased it and put it back in the air. It has worked flawlessly for three years since. I have a connector on my rotator cable so I can take it apart if I need to. I use a rubberized trailer connector that has 8 pins and I have it outside in the tower. Good luck with the antennas.
73
Frank
KL7IPV
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WB2WIK
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Posts: 20547




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« Reply #5 on: September 12, 2002, 01:34:02 PM »

Hi Tom,

Now I understand what you've got.  

The CD-45 is not the control box for the HAM-IV.  The CD-45 is one type of rotator, the HAM-IV is a different type.  You can use a CD-45 control box on a HAM-IV mechanism, I believe, but the "as shipped" HAM-IV has its own control box, which is also labeled HAM-IV.  So, I'm assuming you got this stuff used, and the previous owner did a little "mix & match" work.

The HAM-IV rotor is heavier duty, has more ball bearings, a different bearing race, and a brake mechanism which the CD-45 does not have.

If you have a HAM-IV mechanism and only an MA5B on a 7' mast, I'd forget about the thrust bearing; however, Aluma should have a "factory standard" thrust bearing accessory.  It shouldn't be necessary to homebrew one.

WB2WIK/6
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K4KMG
Member

Posts: 16




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« Reply #6 on: September 12, 2002, 09:30:34 PM »

Thanks Steve & Frank, I live about 1 mile from Aluma. I have even delivered their mail on occasion. Very nice folks! Good idea asking them for a thrust bearing! DUH! I think this getting old stuff is for the birds. I did get the tower and accessories used. How about $100 for all! Not bad I think. Any hint/tips on opening the Ham4. Before I install on the tower I would like to make sure all is ok with the mechanism. It works but has probably not been used for a long time. I am aware of Norms exchange program, but I always hated paying someone for something I could do myself.
Thanks again
Tom F.
K4KMG
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WB2WIK
Member

Posts: 20547




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« Reply #7 on: September 13, 2002, 08:12:50 AM »

I wouldn't open the HAM-IV until something's wrong with it.  The old saw, "If it ain't broke, don't fix it!" definitely applies when it comes to rotors.

The HAM-IV has a ton of ball bearings, all greased, that will drive you nuts chasing them if you make any mistakes during servicing.  And normally, a HAM-IV doesn't require any servicing until it's very old, or very abused, or both.  I've had them last 20+ years in service without a problem of any kind, provided their load was balanced and the CABLE was serviced.  (Cables age far faster than the rotator.)

73 de Steve, WB2WIK/6

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