I was rushed, and I needed some end insulators a few years ago. I decided to
buy a foot of plastic chain at the local hardware store. Cost was 70 cents!!
I cut it into pieces with three chain links on each end. Works okay.
Sent from my iPhone
> On Feb 9, 2020, at 11:59 AM, towertalk-request@contesting.com wrote:
>
> Send TowerTalk mailing list submissions to
> towertalk@contesting.com
>
> To subscribe or unsubscribe via the World Wide Web, visit
> http://lists.contesting.com/mailman/listinfo/towertalk
> or, via email, send a message with subject or body 'help' to
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> When replying, please edit your Subject line so it is more specific
> than "Re: Contents of TowerTalk digest..."
>
>
> Today's Topics:
>
> 1. Re: center insulator material (Joe K2UF)
> 2. Re: Harmonics rectification in bearings or Pro.Sis. Tel
> rotors? (Richard (Rick) Karlquist)
> 3. Re: center insulator material (jimlux)
> 4. Re: center insulator material (Robert Harmon)
> 5. Re: center insulator material (Grant Saviers)
> 6. Re: center insulator material (Wes Attaway (N5WA))
> 7. Re: center insulator material (john@kk9a.com)
> 8. Re: center insulator material (Rob Atkinson)
> 9. Harmonics rectification in bearings or Pro.Sis. Tel rotors?
> (SM0HRP Kari Gustafsson)
> 10. Re: Harmonics rectification in bearings or Pro.Sis. Tel
> rotors? (Grant Saviers)
> 11. Re: center insulator material (john@kk9a.com)
> 12. Re: Harmonics rectification in bearings or Pro.Sis. Tel
> rotors? (K9MA)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Sat, 8 Feb 2020 12:24:18 -0500
> From: "Joe K2UF" <joe@k2uf.com>
> To: "'charlie carroll'" <k1xx@k1xx.com>, <towertalk@contesting.com>
> Subject: Re: [TowerTalk] center insulator material
> Message-ID: <mailman.4099.1581267564.19421.towertalk@contesting.com>
> Content-Type: text/plain; charset="us-ascii"
>
> Hi Charlie,
>
> I use small (about 8x10 inch) black kitchen cutting boards from the local
> box store. I'm not sure what the material is some kind of 'plastic'. I
> have shaped them using a table saw and drill press. I use them for center
> insulators on several dipoles with an so239 mounted in the center and holes
> for the elements and Dacron rope for mounting. I have had these insulators
> for several generations of antennas (maybe 8 to 10 years) and the sun hardly
> fades them at all. Of course I am up here in upstate NY summer sun and no
> salt.)
>
> Good luck
>
> 73 Joe K2UF
>
>
>
> ------------------------------
>
> Message: 2
> Date: Sat, 8 Feb 2020 10:29:02 -0800
> From: "Richard (Rick) Karlquist" <richard@karlquist.com>
> To: Grant Saviers <grants2@pacbell.net>, SM0HRP Kari Gustafsson
> <kari@sm0hrp.se>, towertalk@contesting.com
> Subject: Re: [TowerTalk] Harmonics rectification in bearings or
> Pro.Sis. Tel rotors?
> Message-ID: <f2f2eca8-cc68-c3d2-f1ab-a4e6a04e7821@karlquist.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> A long time ago I had a Rohn 25 tower with a Yagi on top turned
> by a Ham-M rotor. I experienced severe TVI on channel 2. Somehow,
> I don't know why, I got the idea that the bearings were rectifying.
> I put a jumper loop of wire across the two halves of the Ham-M
> and the TVI completely disappeared and never returned.
>
> Rick N6RK
>
>>> On 2/8/2020 03:42, SM0HRP Kari Gustafsson wrote:
>>> Hi,
>>>
>>> I have discovered what it seems like rectification in my HD Alu Tower
>>> where
>>> on the top there is antenna ball bearing thrust (SKF) below a 61D
>>> Prosistel
>>> rotor. I used various techniques to pin poin to the tower.
>>>
>
>>> 73s Kari SM0HRP
>>>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 8 Feb 2020 10:47:30 -0800
> From: jimlux <jimlux@earthlink.net>
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] center insulator material
> Message-ID: <87206835-88ec-c9bf-2460-afe1172b31aa@earthlink.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
>> On 2/8/20 8:57 AM, charlie carroll wrote:
>> I need some help selecting some type of material to build some custom
>> center insulators.? I have what approaches zero experience in this area.
>>
>> The insulators will be used to support near vertical dipoles for
>> 160-meters.? The antennas will be installed in the Caribbean and will
>> need high resistance to UV and salt water.? I also want to install an
>> SO-239 and home made common-mode choke on the insulator.? It would be
>> preferable that I be able to fabricate the final shape with common home
>> workshop tools and not have to rely on a machine shop.? The insulators
>> won't be under a lot of tension because of their orientation, but low
>> weight material would be preferred.? The insulators may be subject to
>> some winds containing sand particles.
>>
>> I'm looking for some help selecting some appropriate material (UHMW,
>> Ultem, UV augmented HDPE, ...) that I can investigate further.
>>
>
> Most any UV resistant plastic would work. The shape is almost
> immaterial, you can get flat bar stock, drill holes, and be done.
>
> http://www.sdplastics.com/ultravioletresistance.html has a bunch of info.
>
> I've used Acetal Copolymer (aka Delrin) with UV inhibitors. There's
> decades of experience with it. Ultem is very good (we use it on
> spacecraft), but probably costs more than what you want.
>
> Looking at the McMaster Carr catalog, i see they they have a VHMW
> Polyethylene which is weather resistant. I'm not sure that I'd use PE
> though.
>
>
> Speaking of machine shops - you might look at one of the prototyping
> companies like First Cut Protolabs:
> https://www.protolabs.com/services/cnc-machining/ - there's a fair
> number of these places around, and they typically stock all the useful
> materials, and will turn it around in a few days.
>
>
>
> ------------------------------
>
> Message: 4
> Date: Sat, 8 Feb 2020 13:17:15 -0800
> From: Robert Harmon <k6uj@pacbell.net>
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] center insulator material
> Message-ID: <793B4A46-613E-4513-8330-28AB99CC6068@pacbell.net>
> Content-Type: text/plain; charset=us-ascii
>
> Joe,
>
> I also use the plastic cutting boards for insulator material. I use the
> white ones, they are about 3/8" thick.
> I have been using them like you about 10 years and no problems from the sun.
> Nice and easy to cut
> and drill. I round the corners around the drilled holes so no sharp corners
> to cut the antenna rope.
>
> Great minds think alike :-)
>
> 73,
> Bob
> K6UJ
>
>
>
>
>> On Feb 8, 2020, at 9:24 AM, Joe K2UF <joe@k2uf.com> wrote:
>>
>> Hi Charlie,
>>
>> I use small (about 8x10 inch) black kitchen cutting boards from the local
>> box store. I'm not sure what the material is some kind of 'plastic'. I
>> have shaped them using a table saw and drill press. I use them for center
>> insulators on several dipoles with an so239 mounted in the center and holes
>> for the elements and Dacron rope for mounting. I have had these insulators
>> for several generations of antennas (maybe 8 to 10 years) and the sun hardly
>> fades them at all. Of course I am up here in upstate NY summer sun and no
>> salt.)
>>
>> Good luck
>>
>> 73 Joe K2UF
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
> ------------------------------
>
> Message: 5
> Date: Sat, 8 Feb 2020 13:27:05 -0800
> From: Grant Saviers <grants2@pacbell.net>
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] center insulator material
> Message-ID: <00974ae3-f415-20ff-3e77-24b0b706a0c9@pacbell.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I've been using black UHMW for mast radial bearings - cheap, slippery,
> good insulator, and UV resistant (just inspected after 4 years). Not as
> strong as delrin or glass filled, but should work fine for your center
> insulators.
>
> One BIG caution using home shop tools - soft plastics (also brass) will
> grab a standard twist drill flutes and pull it out of most any vise.
> That makes for a whirling finger/hand slicer. It is important to stone
> the sharp drill point cutting edges flat for about 0.020 - 0.030" for
> drills bigger than 3/16" diameter or so. Sometimes called dubbing the
> drill point, see
>
> https://www.bing.com/videos/search?q=drilling+brass&docid=608050047239851308&mid=00A1314A97BD2D20C1D800A1314A97BD2D20C1D8&view=detail&FORM=VIRE
>
> https://handycrowd.com/drilling-brass-the-easy-and-safe-way/
>
> Grant KZ1W
>
>> On 2/8/2020 10:47, jimlux wrote:
>>> On 2/8/20 8:57 AM, charlie carroll wrote:
>>> I need some help selecting some type of material to build some custom
>>> center insulators.? I have what approaches zero experience in this area.
>>>
>>> The insulators will be used to support near vertical dipoles for
>>> 160-meters.? The antennas will be installed in the Caribbean and will
>>> need high resistance to UV and salt water.? I also want to install an
>>> SO-239 and home made common-mode choke on the insulator.? It would be
>>> preferable that I be able to fabricate the final shape with common
>>> home workshop tools and not have to rely on a machine shop.? The
>>> insulators won't be under a lot of tension because of their
>>> orientation, but low weight material would be preferred.? The
>>> insulators may be subject to some winds containing sand particles.
>>>
>>> I'm looking for some help selecting some appropriate material (UHMW,
>>> Ultem, UV augmented HDPE, ...) that I can investigate further.
>>>
>>
>> Most any UV resistant plastic would work. The shape is almost
>> immaterial, you can get flat bar stock, drill holes, and be done.
>>
>> http://www.sdplastics.com/ultravioletresistance.html has a bunch of info.
>>
>> I've used Acetal Copolymer (aka Delrin) with UV inhibitors. There's
>> decades of experience with it. Ultem is very good (we use it on
>> spacecraft), but probably costs more than what you want.
>>
>> Looking at the McMaster Carr catalog, i see they they have a VHMW
>> Polyethylene which is weather resistant.? I'm not sure that I'd use PE
>> though.
>>
>>
>> Speaking of machine shops - you might look at one of the prototyping
>> companies like First Cut Protolabs:
>> https://www.protolabs.com/services/cnc-machining/ - there's a fair
>> number of these places around, and they typically stock all the useful
>> materials, and will turn it around in a few days.
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> ------------------------------
>
> Message: 6
> Date: Sat, 8 Feb 2020 16:41:32 -0600
> From: "Wes Attaway \(N5WA\)" <wesattaway@bellsouth.net>
> To: "'charlie carroll'" <k1xx@k1xx.com>, <towertalk@contesting.com>
> Subject: Re: [TowerTalk] center insulator material
> Message-ID: <FC3C3A2F7827469D846504281002132A@Office1>
> Content-Type: text/plain; charset="iso-8859-1"
>
> Jim Brown has a real good article with lots of data re end-feeding a
> vertical dipole. The antenna works really well.
>
> http://www.k9yc.com/VerticalDipole.pdf
>
> -------------------
> Wes Attaway (N5WA)
> (318) 393-3289 - Shreveport, LA
> Computer/Cellphone Forensics
> AttawayForensics.com
> -------------------
>
> -----Original Message-----
> From: TowerTalk [mailto:towertalk-bounces@contesting.com] On Behalf Of
> charlie carroll
> Sent: Saturday, February 08, 2020 10:57 AM
> To: towertalk@contesting.com
> Subject: [TowerTalk] center insulator material
>
> I need some help selecting some type of material to build some custom
> center insulators.? I have what approaches zero experience in this area.
>
> The insulators will be used to support near vertical dipoles for
> 160-meters.? The antennas will be installed in the Caribbean and will
> need high resistance to UV and salt water.? I also want to install an
> SO-239 and home made common-mode choke on the insulator.? It would be
> preferable that I be able to fabricate the final shape with common home
> workshop tools and not have to rely on a machine shop.? The insulators
> won't be under a lot of tension because of their orientation, but low
> weight material would be preferred.? The insulators may be subject to
> some winds containing sand particles.
>
> I'm looking for some help selecting some appropriate material (UHMW,
> Ultem, UV augmented HDPE, ...) that I can investigate further.
>
> thanks
>
> 73 charlie, k1xx
> _______________________________________________
>
>
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
> ------------------------------
>
> Message: 7
> Date: Sun, 9 Feb 2020 01:36:43 -0000
> From: <john@kk9a.com>
> To: <towertalk@contesting.com>
> Subject: Re: [TowerTalk] center insulator material
> Message-ID: <003f01d5dee9$6380f680$2a82e380$@com>
> Content-Type: text/plain; charset="us-ascii"
>
> Have you considered a commercial product? When I was looking for a dipole
> canter for an expedition to WP2AA I really did not like most of the
> commercial ones that I saw so I inquired on Towertalk. The Budwig was
> suggested and I purchased a couple of them. It is a simple device but it
> worked well for me, I have no idea how it holds up over long term UV/salt
> spray but I would expect it to last at least as long as your coax.
>
> John KK9A
>
> From: charlie carroll k1xx
> Sat Feb 8 11:57:24 EST 2020
>
> I need some help selecting some type of material to build some custom
> center insulators. I have what approaches zero experience in this area.
>
> The insulators will be used to support near vertical dipoles for
> 160-meters. The antennas will be installed in the Caribbean and will
> need high resistance to UV and salt water. I also want to install an
> SO-239 and home made common-mode choke on the insulator. It would be
> preferable that I be able to fabricate the final shape with common home
> workshop tools and not have to rely on a machine shop. The insulators
> won't be under a lot of tension because of their orientation, but low
> weight material would be preferred. The insulators may be subject to
> some winds containing sand particles.
>
> I'm looking for some help selecting some appropriate material (UHMW,
> Ultem, UV augmented HDPE, ...) that I can investigate further.
>
> thanks
>
> 73 charlie, k1xx
>
>
>
> ------------------------------
>
> Message: 8
> Date: Sun, 9 Feb 2020 06:43:07 -0600
> From: Rob Atkinson <ranchorobbo@gmail.com>
> To: towertalk <towertalk@contesting.com>
> Subject: Re: [TowerTalk] center insulator material
> Message-ID:
> <CALWD7Z4kriiPEm7+3wxBHwL9biVQm1MhaAXF9sFfbh+dNb4xhA@mail.gmail.com>
> Content-Type: text/plain; charset="UTF-8"
>
> What's wrong with the good old ceramic dog bone center insulator?
>
> But forget the 160 m. vertical dipole; I want to know how you're going
> to ship and put up the 260 foot tower to hold it.
>
> 73
> Rob
> K5UJ
>
>
> ------------------------------
>
> Message: 9
> Date: Sun, 9 Feb 2020 14:57:58 +0100
> From: "SM0HRP Kari Gustafsson" <kari@sm0hrp.se>
> To: <towertalk@contesting.com>
> Subject: [TowerTalk] Harmonics rectification in bearings or Pro.Sis.
> Tel rotors?
> Message-ID: <000001d5df50$ef8adad0$cea09070$@sm0hrp.se>
> Content-Type: text/plain; charset="us-ascii"
>
> Interesting Grant. I wonder though how common this problem is. So I need to
> make ground loop that can make revolution round the tower when the antenna
> is being rotated. Yes I agree, to model a Yagi above a rotor would be
> interesting to do. Perhaps someone already have done that?
> 73s Kari SM0HRP
>
>
> From: Grant Saviers <grants2@pacbell.net>
> To: SM0HRP Kari Gustafsson <kari@sm0hrp.se>, towertalk@contesting.com
> Subject: Re: [TowerTalk] Harmonics rectification in bearings or
> Pro.Sis. Tel rotors?
> Message-ID: <4396e89b-c67e-d672-28f0-e4fdb5ed23ef@pacbell.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Considering that the oil film in a well lubricated ball bearing is only a
> few microns thick, it doesn't take much voltage to bridge that gap.
> However, it is likely there are wear particles and worse rust added to the
> mix. Then there is the additional problem of metal to metal contact and
> fretting corrosion when the balls don't rotate enough to be lubricated.
> Which happens when rotators sit on a heading and move a bit in the wind. So
> the noise could be rectification or just arcing.
>
> All lubricated bearings should have a ground lead jumper around them. I
> learned this long ago making disk drives and used rotating contacts of
> various types. Grounds are also needed in inverter driven motors where high
> (RF) frequencies couple to the armature and arc thru the well lubed bearing
> to the frame. It kills the bearings. google it.
>
> It might be informative to model a free space mast with a top yagi at QRO
> and see what the voltage would be at the rotator end.
>
> Grant KZ1W
>
>> On 2/8/2020 03:42, SM0HRP Kari Gustafsson wrote:
>> Hi,
>>
>> I have discovered what it seems like rectification in my HD Alu Tower
>> where on the top there is antenna ball bearing thrust (SKF) below a
>> 61D Prosistel rotor. I used various techniques to pin poin to the tower.
>>
>> The harmonics is growl sounding on 20 m (TX on 40 m) and is some -120
>> dB below the fundamental (40 m) after double low- and high as filters
>> (giving some 100 dB of combined out of band suppression) in TX and RX
> chain.
>>
>> I have read that some have encountered harmonics rectification in
>> thrust bearings. Anyone has any experience from ball bearings and
>> rectification? Or rectification in Prosistel rotors (in the
> potentiometer?).
>>
>> Being a physicist I wonder how the mechanism is with this kind of
>> rectification in bearings and grease which I assume is isolating. Or?
>>
>> I am close to getting a skylift and do the shortening of the bearing
>> with a jumper and see if it helps bit it is winter her. Brr.cold.
>>
>> 73s Kari SM0HRP
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk@contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>>
>
>
> ------------------------------
>
> Message: 3
> Date: Sat, 8 Feb 2020 11:57:24 -0500
> From: charlie carroll <k1xx@k1xx.com>
> To: towertalk@contesting.com
> Subject: [TowerTalk] center insulator material
> Message-ID: <c827acc2-675f-c92c-b34c-a9625e2d2b18@k1xx.com>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I need some help selecting some type of material to build some custom center
> insulators.? I have what approaches zero experience in this area.
>
> The insulators will be used to support near vertical dipoles for
> 160-meters.? The antennas will be installed in the Caribbean and will need
> high resistance to UV and salt water.? I also want to install an
> SO-239 and home made common-mode choke on the insulator.? It would be
> preferable that I be able to fabricate the final shape with common home
> workshop tools and not have to rely on a machine shop.? The insulators won't
> be under a lot of tension because of their orientation, but low weight
> material would be preferred.? The insulators may be subject to some winds
> containing sand particles.
>
> I'm looking for some help selecting some appropriate material (UHMW, Ultem,
> UV augmented HDPE, ...) that I can investigate further.
>
> thanks
>
> 73 charlie, k1xx
>
>
> ------------------------------
>
> Subject: Digest Footer
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> ------------------------------
>
> End of TowerTalk Digest, Vol 206, Issue 5
> *****************************************
>
>
>
> ------------------------------
>
> Message: 10
> Date: Sun, 9 Feb 2020 06:23:56 -0800
> From: Grant Saviers <grants2@pacbell.net>
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Harmonics rectification in bearings or
> Pro.Sis. Tel rotors?
> Message-ID: <68e47d2b-7135-ce74-e779-476bb8e61d6f@pacbell.net>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> Kari,
>
> Not sure if you have a rotating tower or rotating mast. For my masts,
> the ground wire loop is the same design as the coax service loop at the
> top of the tower, they can be taped together. A u-bolt on the mast for
> one end and a lug onto a screw on the tower top for the other. Or
> perhaps inside the tower on a rotator top clamp bolt and then to the tower.
>
> I use 10ga wire but that is because I had some high flex. 1mm would be
> fine.
>
> btw corona discharge (aka p-static) is another mast current that kills
> ball bearings.
>
> Grant KZ1W
>
>> On 2/9/2020 05:57, SM0HRP Kari Gustafsson wrote:
>> Interesting Grant. I wonder though how common this problem is. So I need to
>> make ground loop that can make revolution round the tower when the antenna
>> is being rotated. Yes I agree, to model a Yagi above a rotor would be
>> interesting to do. Perhaps someone already have done that?
>> 73s Kari SM0HRP
>>
>>
>> From: Grant Saviers <grants2@pacbell.net>
>> To: SM0HRP Kari Gustafsson <kari@sm0hrp.se>, towertalk@contesting.com
>> Subject: Re: [TowerTalk] Harmonics rectification in bearings or
>> Pro.Sis. Tel rotors?
>> Message-ID: <4396e89b-c67e-d672-28f0-e4fdb5ed23ef@pacbell.net>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>>
>> Considering that the oil film in a well lubricated ball bearing is only a
>> few microns thick, it doesn't take much voltage to bridge that gap.
>> However, it is likely there are wear particles and worse rust added to the
>> mix. Then there is the additional problem of metal to metal contact and
>> fretting corrosion when the balls don't rotate enough to be lubricated.
>> Which happens when rotators sit on a heading and move a bit in the wind. So
>> the noise could be rectification or just arcing.
>>
>> All lubricated bearings should have a ground lead jumper around them. I
>> learned this long ago making disk drives and used rotating contacts of
>> various types. Grounds are also needed in inverter driven motors where high
>> (RF) frequencies couple to the armature and arc thru the well lubed bearing
>> to the frame. It kills the bearings. google it.
>>
>> It might be informative to model a free space mast with a top yagi at QRO
>> and see what the voltage would be at the rotator end.
>>
>> Grant KZ1W
>>
>>> On 2/8/2020 03:42, SM0HRP Kari Gustafsson wrote:
>>> Hi,
>>>
>>> I have discovered what it seems like rectification in my HD Alu Tower
>>> where on the top there is antenna ball bearing thrust (SKF) below a
>>> 61D Prosistel rotor. I used various techniques to pin poin to the tower.
>>>
>>> The harmonics is growl sounding on 20 m (TX on 40 m) and is some -120
>>> dB below the fundamental (40 m) after double low- and high as filters
>>> (giving some 100 dB of combined out of band suppression) in TX and RX
>> chain.
>>>
>>> I have read that some have encountered harmonics rectification in
>>> thrust bearings. Anyone has any experience from ball bearings and
>>> rectification? Or rectification in Prosistel rotors (in the
>> potentiometer?).
>>>
>>> Being a physicist I wonder how the mechanism is with this kind of
>>> rectification in bearings and grease which I assume is isolating. Or?
>>>
>>> I am close to getting a skylift and do the shortening of the bearing
>>> with a jumper and see if it helps bit it is winter her. Brr.cold.
>>>
>>> 73s Kari SM0HRP
>>>
>>> _______________________________________________
>>>
>>>
>>>
>>> _______________________________________________
>>> TowerTalk mailing list
>>> TowerTalk@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>
>>
>>
>> ------------------------------
>>
>> Message: 3
>> Date: Sat, 8 Feb 2020 11:57:24 -0500
>> From: charlie carroll <k1xx@k1xx.com>
>> To: towertalk@contesting.com
>> Subject: [TowerTalk] center insulator material
>> Message-ID: <c827acc2-675f-c92c-b34c-a9625e2d2b18@k1xx.com>
>> Content-Type: text/plain; charset=utf-8; format=flowed
>>
>> I need some help selecting some type of material to build some custom center
>> insulators.? I have what approaches zero experience in this area.
>>
>> The insulators will be used to support near vertical dipoles for
>> 160-meters.? The antennas will be installed in the Caribbean and will need
>> high resistance to UV and salt water.? I also want to install an
>> SO-239 and home made common-mode choke on the insulator.? It would be
>> preferable that I be able to fabricate the final shape with common home
>> workshop tools and not have to rely on a machine shop.? The insulators won't
>> be under a lot of tension because of their orientation, but low weight
>> material would be preferred.? The insulators may be subject to some winds
>> containing sand particles.
>>
>> I'm looking for some help selecting some appropriate material (UHMW, Ultem,
>> UV augmented HDPE, ...) that I can investigate further.
>>
>> thanks
>>
>> 73 charlie, k1xx
>>
>>
>> ------------------------------
>>
>> Subject: Digest Footer
>>
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>> ------------------------------
>>
>> End of TowerTalk Digest, Vol 206, Issue 5
>> *****************************************
>>
>> _______________________________________________
>>
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>
>
> ------------------------------
>
> Message: 11
> Date: Sun, 09 Feb 2020 09:53:16 -0600
> From: john@kk9a.com
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] center insulator material
> Message-ID:
> <20200209095316.Horde.0KEPhQf5ixNeerBsOJJwEqQ@www11.qth.com>
> Content-Type: text/plain; charset=utf-8; format=flowed; DelSp=Yes
>
> That is a good question. Perhaps they have access to a commercial
> tower, there is a 300' tower in the background on the second photo of
> my PJ4R page http://www.qrz.com/db/pj4r that has been used on top
> band. Other options are loading coils or to fold the ends into a C
> shape. The C works very well however I would call it that and not a
> vertical dipole.
>
> John KK9A
>
>
> Rob Atkinson K5JU wrote:
>
>
> But forget the 160 m. vertical dipole; I want to know how you're going
> to ship and put up the 260 foot tower to hold it.
>
> 73
> Rob
> K5UJ
>
>
>
> ------------------------------
>
> Message: 12
> Date: Sun, 9 Feb 2020 10:59:19 -0600
> From: K9MA <k9ma@sdellington.us>
> To: towertalk@contesting.com
> Subject: Re: [TowerTalk] Harmonics rectification in bearings or
> Pro.Sis. Tel rotors?
> Message-ID: <1ee94853-6eec-a289-2959-353456b939e2@sdellington.us>
> Content-Type: text/plain; charset=utf-8; format=flowed
>
> I just use a piece of braid inside the tower from the mast to the tower.
> Because of the small diameter of the mast, it doesn't take much to make
> a loop. It bypasses both the rotator and the thrust bearing.
>
> 73,
> Scott K9MA
>
>
>
>> On 2/9/2020 08:23, Grant Saviers wrote:
>> Kari,
>>
>> Not sure if you have a rotating tower or rotating mast.? For my masts,
>> the ground wire loop is the same design as the coax service loop at
>> the top of the tower, they can be taped together.? A u-bolt on the
>> mast for one end and a lug onto a screw on the tower top for the
>> other.? Or perhaps inside the tower on a rotator top clamp bolt and
>> then to the tower.
>>
>> I use 10ga wire but that is because I had some high flex.? 1mm would
>> be fine.
>>
>> btw corona discharge (aka p-static) is another mast current that kills
>> ball bearings.
>>
>> Grant KZ1W
>>
>>> On 2/9/2020 05:57, SM0HRP Kari Gustafsson wrote:
>>> Interesting Grant. I wonder though how common this problem is. So I?
>>> need to
>>> make ground loop that can make revolution round the tower when the
>>> antenna
>>> is being rotated. Yes I agree, to model a Yagi above a rotor would be
>>> interesting to do. Perhaps someone already have done that?
>>> 73s Kari SM0HRP
>>>
>>>
>>> From: Grant Saviers <grants2@pacbell.net>
>>> To: SM0HRP Kari Gustafsson <kari@sm0hrp.se>, towertalk@contesting.com
>>> Subject: Re: [TowerTalk] Harmonics rectification in bearings or
>>> ????Pro.Sis. Tel rotors?
>>> Message-ID: <4396e89b-c67e-d672-28f0-e4fdb5ed23ef@pacbell.net>
>>> Content-Type: text/plain; charset=utf-8; format=flowed
>>>
>>> Considering that the oil film in a well lubricated ball bearing is
>>> only a
>>> few microns thick, it doesn't take much voltage to bridge that gap.
>>> However, it is likely there are wear particles and worse rust added
>>> to the
>>> mix.? Then there is the additional problem of metal to metal contact and
>>> fretting corrosion when the balls don't rotate enough to be lubricated.
>>> Which happens when rotators sit on a heading and move a bit in the
>>> wind.? So
>>> the noise could be rectification or just arcing.
>>>
>>> All lubricated bearings should have a ground lead jumper around them.? I
>>> learned this long ago making disk drives and used rotating contacts of
>>> various types. Grounds are also needed in inverter driven motors
>>> where high
>>> (RF) frequencies couple to the armature and arc thru the well lubed
>>> bearing
>>> to the frame.? It kills the bearings. google it.
>>>
>>> It might be informative to model a free space mast with a top yagi at
>>> QRO
>>> and see what the voltage would be at the rotator end.
>>>
>>> Grant KZ1W
>>>
>>> On 2/8/2020 03:42, SM0HRP Kari Gustafsson wrote:
>>>> Hi,
>>>>
>>>> I have discovered what it seems like rectification in my HD Alu Tower
>>>> where on the top there is antenna ball bearing thrust (SKF) below a
>>>> 61D Prosistel rotor. I used various techniques to pin poin to the
>>>> tower.
>>>>
>>>> The harmonics is growl sounding on 20 m (TX on 40 m) and is some -120
>>>> dB below the fundamental (40 m) after double low- and high as filters
>>>> (giving some 100 dB of combined out of band suppression) in TX and RX
>>> chain.
>>>>
>>>> I have read that some have encountered harmonics rectification in
>>>> thrust bearings. Anyone has any experience from ball bearings and
>>>> rectification? Or rectification in Prosistel rotors (in the
>>> potentiometer?).
>>>>
>>>> Being a physicist I wonder how the mechanism is with this kind of
>>>> rectification in bearings and grease which I assume is isolating. Or?
>>>>
>>>> I am close to getting a skylift and do the shortening of the bearing
>>>> with a jumper and see if it helps bit it is winter her. Brr.cold.
>>>>
>>>> 73s Kari SM0HRP
>>>>
>>>> _______________________________________________
>>>>
>>>>
>>>>
>>>> _______________________________________________
>>>> TowerTalk mailing list
>>>> TowerTalk@contesting.com
>>>> http://lists.contesting.com/mailman/listinfo/towertalk
>>>>
>>>
>>>
>>> ------------------------------
>>>
>>> Message: 3
>>> Date: Sat, 8 Feb 2020 11:57:24 -0500
>>> From: charlie carroll <k1xx@k1xx.com>
>>> To: towertalk@contesting.com
>>> Subject: [TowerTalk] center insulator material
>>> Message-ID: <c827acc2-675f-c92c-b34c-a9625e2d2b18@k1xx.com>
>>> Content-Type: text/plain; charset=utf-8; format=flowed
>>>
>>> I need some help selecting some type of material to build some custom
>>> center
>>> insulators.? I have what approaches zero experience in this area.
>>>
>>> The insulators will be used to support near vertical dipoles for
>>> 160-meters.? The antennas will be installed in the Caribbean and will
>>> need
>>> high resistance to UV and salt water.? I also want to install an
>>> SO-239 and home made common-mode choke on the insulator.? It would be
>>> preferable that I be able to fabricate the final shape with common home
>>> workshop tools and not have to rely on a machine shop.? The
>>> insulators won't
>>> be under a lot of tension because of their orientation, but low weight
>>> material would be preferred.? The insulators may be subject to some
>>> winds
>>> containing sand particles.
>>>
>>> I'm looking for some help selecting some appropriate material (UHMW,
>>> Ultem,
>>> UV augmented HDPE, ...) that I can investigate further.
>>>
>>> thanks
>>>
>>> 73 charlie, k1xx
>>>
>>>
>>> ------------------------------
>>>
>>> Subject: Digest Footer
>>>
>
> --
> Scott K9MA
>
> k9ma@sdellington.us
>
>
>
> ------------------------------
>
> Subject: Digest Footer
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> ------------------------------
>
> End of TowerTalk Digest, Vol 206, Issue 6
> *****************************************
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