[TowerTalk] TowerTalk Digest, Vol 149, Issue 22
Denis Coolican
coolican at telus.net
Fri May 15 13:39:49 EDT 2015
----- Original Message -----
From: <towertalk-request at contesting.com>
To: <towertalk at contesting.com>
Sent: Tuesday, May 12, 2015 2:15 PM
Subject: TowerTalk Digest, Vol 149, Issue 22
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> Today's Topics:
>
> 1. Current Choke for Ladder Line (Hans Hammarquist via TowerTalk)
> 2. Re: Current Choke for Ladder Line (Jim Brown)
> 3. Re: Current Choke for Ladder Line (Bry Carling)
> 4. Re: Current Choke for Ladder Line (Jim Brown)
> 5. Mast inquiries (Patrick Greenlee)
> 6. Balun S Parameter (Karin Johnson)
> 7. FREE Tower parts in Central Florida (Bry Carling AF4K)
> 8. Re: Rohn towers (Bry Carling AF4K)
> 9. Re: Current Choke for Ladder Line (Bry Carling AF4K)
> 10. Re: Current Choke for Ladder Line (Bry Carling AF4K)
>
>
> ----------------------------------------------------------------------
>
> Message: 1
> Date: Tue, 12 May 2015 14:01:29 -0400
> From: Hans Hammarquist via TowerTalk <towertalk at contesting.com>
> To: towertalk at contesting.com
> Subject: [TowerTalk] Current Choke for Ladder Line
> Message-ID: <14d4949e6e0-3e03-17f6e at webprd-m59.mail.aol.com>
> Content-Type: text/plain; charset=utf-8
>
> Gentlemen,
>
>
> I have seen many articles how to build and/or buy common mode chokes for
> coax cables but I don't remember any articles how to build (or buy) and
> choke for a 400 ohm ladder line.
>
>
> The common mode current on a ladder line is causing the same problem as a
> common mode current on a coax. i have a choke between my tuner and radio
> which reduced noise quite good but wonder now how much RF power I radiate
> and signal I receive from the CM current in the feeder to my OCF dipole.
>
>
> Any ideas/comments?
>
> Hans - N2JFS
>
>
> ------------------------------
>
> Message: 2
> Date: Tue, 12 May 2015 11:28:45 -0700
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Current Choke for Ladder Line
> Message-ID: <5552465D.5040304 at audiosystemsgroup.com>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> On Tue,5/12/2015 11:01 AM, Hans Hammarquist via TowerTalk wrote:
>> Gentlemen,
>>
>>
>> I have seen many articles how to build and/or buy common mode chokes for
>> coax cables but I don't remember any articles how to build (or buy) and
>> choke for a 400 ohm ladder line.
>
> That's because no one has thought of one that works. An important
> component of the problem is that the Zo of practical two-wire chokes
> wound on ferrite toroids is much lower than 400 Ohms. For example,
> close-spaced enameled wire yields about 50 ohms, close-spaced THHN
> (house wire) yields about 90 ohms.
>
> Another important component of the problem is that, because the
> feedpoint is off-center, the common mode voltage gets VERY high if
> you're running much power, so the dissipation in the choke is likely to
> fry it.
>
> A third reason is the concentrated differential mode dissipation in the
> turns of line when the antenna is poorly matched to the line.
>
>> The common mode current on a ladder line is causing the same problem as a
>> common mode current on a coax.
>
> Exactly right.
>
>> i have a choke between my tuner and radio which reduced noise quite good
>> but wonder now how much RF power I radiate and signal I receive from the
>> CM current in the feeder to my OCF dipole.
>
> The only other practical way to kill common mode on high Z line would be
> with a conventional 2-winding transformer capable of handling the power.
> Fair-Rite #61 might be good enough for moderate power levels below about
> 12 MHz, but its losses increase above that frequency. Fair-Rite #67
> would be a better candidate -- its losses remain quite low up to about
> 40 MHz, and are not bad at 50 MHz. On the graphs below, u's is the mu
> that defines inductance, and u''s is the loss component in a series
> equivalent circuit.
>
> http://www.fair-rite.com/newfair/materials61.htm
>
> http://www.fair-rite.com/newfair/materials67.htm
>
> http://www.fair-rite.com/cgibin/catalog.pgm?THEAPPL=Inductive+Components&THEWHERE=Closed+Magnetic+Circuit&THEPART=Toroids#select:freq1
>
> 73, Jim K9YC
>
>
>
> ------------------------------
>
> Message: 3
> Date: Tue, 12 May 2015 14:30:14 -0400
> From: Bry Carling <bcarling at cfl.rr.com>
> To: Hans Hammarquist <hanslg at aol.com>
> Cc: "towertalk at contesting.com" <towertalk at contesting.com>
> Subject: Re: [TowerTalk] Current Choke for Ladder Line
> Message-ID: <3C35924F-0625-4F3C-AF9C-098870B63ACE at cfl.rr.com>
> Content-Type: text/plain; charset=us-ascii
>
> From what I have read lately you can just put 6 or 8 of those snap on
> ferrite beads near the end of the coax.
>
> That's what is inside most of those current chokes sold on the web for ten
> times the price.
>
> Best regards - Brian Carling
> AF4K Crystals Co.
> 117 Sterling Pine St.
> Sanford, FL 32773
>
> Tel: +USA 321-262-5471
>
>
>
>
>> On May 12, 2015, at 2:01 PM, Hans Hammarquist via TowerTalk
>> <towertalk at contesting.com> wrote:
>>
>> Gentlemen,
>>
>>
>> I have seen many articles how to build and/or buy common mode chokes for
>> coax cables but I don't remember any articles how to build (or buy) and
>> choke for a 400 ohm ladder line.
>>
>>
>> The common mode current on a ladder line is causing the same problem as a
>> common mode current on a coax. i have a choke between my tuner and radio
>> which reduced noise quite good but wonder now how much RF power I radiate
>> and signal I receive from the CM current in the feeder to my OCF dipole.
>>
>>
>> Any ideas/comments?
>>
>> Hans - N2JFS
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> ------------------------------
>
> Message: 4
> Date: Tue, 12 May 2015 11:41:41 -0700
> From: Jim Brown <jim at audiosystemsgroup.com>
> To: towertalk at contesting.com
> Subject: Re: [TowerTalk] Current Choke for Ladder Line
> Message-ID: <55524965.20303 at audiosystemsgroup.com>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> On Tue,5/12/2015 11:30 AM, Bry Carling wrote:
>> >From what I have read lately you can just put 6 or 8 of those snap on
>> >ferrite beads near the end of the coax.
>
> Bad idea -- they don't work well, because they're optimized for VHF. See
> http://k9yc.com/CoaxChokesPPT.pdf
>
>>
>> That's what is inside most of those current chokes sold on the web for
>> ten times the price.
>
> Right.
>
> 73, Jim K9YC
>
>
> ------------------------------
>
> Message: 5
> Date: Tue, 12 May 2015 14:22:58 -0500
> From: Patrick Greenlee <patrick_g at windstream.net>
> To: towertalk at contesting.com
> Subject: [TowerTalk] Mast inquiries
> Message-ID: <55525312.8050000 at windstream.net>
> Content-Type: text/plain; charset=windows-1252; format=flowed
>
> On the HRO Web site:
>
> *Detailed Product Description*
> US Tower offers three different types of masts. The M-5, 10, 15 and 20
> masts have .120" wall thickness. The M-15R and 20R have steel pipe
> inserts in the lower half of the mast which provides extra strength
> where most needed without adding unnecessary weight in the top portion.
> The M-15R and 20R have a thickness of .250".
>
>
> On the UST web site there is also listed CM alloy tube that is 2 inch
> OD and 0.375 wall thickness.
>
> Can someone please give me an explanation of the comment above regarding
> the extra strength where needed in the lower half of the mast? Does
> this assume the lower part of the mast is still above the thrust
> bearing? I can see how the leverage of the part of the mast above the
> top bearing would try to fold the mast at the upper bearing. I see how
> lateral force on the part of the mast above the thrust bearing is
> distributed to the rotator acording to the comparative lever arm
> lengths: 1. rotator to thrust bearing distance and 2. thrust bearing to
> the antenna's center of lateral resistance ( like CG but for
> aerodynamics.) If their statement is true in the case where the
> reinforced part of the mast is below the thrust bearing then I need it
> explained to me.
>
> Also, while on this topic, how does the reinforced-at-the-bottom mast
> compare to the CM tube with .250 wall.
>
> Any thoughts on the efficacy of upgrading to the .375 wall CM tubing?
> Is it overkill and a waste of $ or just slightly belt and suspemnders
> and worth considering? My application is a SteppIR DB42 with 80m and 6m
> accessories plus a NN4ZZ TiltPlate atop a Tashjian HD LM354 turned by a
> Kurt Andress PropPitch motor with the antenna height above ground of 94
> ft or so due to mounting the Tash Tower on a 40 ft steel structure. I
> intend to only have the mast a couple feet or so above the top of the
> tower unless I use the .375 wall CM tube for the mast. Note: the tower
> site is more or less at heart of tornado alley a few miles from
> locations that repetitively are in the news for tornado damage.
>
> Thanks for your consideration.
>
> Patrick NJ5G
>
>
> ------------------------------
>
> Message: 6
> Date: Tue, 12 May 2015 14:28:02 -0400
> From: "Karin Johnson" <karinann at tampabay.rr.com>
> To: <towertalk at contesting.com>
> Subject: [TowerTalk] Balun S Parameter
> Message-ID: <C77F792FEA5F4E828EF7B4AADFAD608C at karinspc>
> Content-Type: text/plain; charset="us-ascii"
>
> Can anyone on the list provide me with the full two port S parameters
> for the DX Engineering 50 to 100 ohm balun?
> The DX Engineering part number is DXE-BAL100-H11-C
>
> Thanks
> Karin K3UU
>
>
>
>
> ------------------------------
>
> Message: 7
> Date: Tue, 12 May 2015 16:06:03 -0400
> From: "Bry Carling AF4K" <bcarling at cfl.rr.com>
> To: towertalk at contesting.com
> Subject: [TowerTalk] FREE Tower parts in Central Florida
> Message-ID: <55525D2B.30899.3E1FB1 at bcarling.cfl.rr.com>
> Content-Type: text/plain; charset=US-ASCII
>
> FREE tower parts
>
> Rohn 25G top section - flat top with hole. Can be used with bearing or
> not.
> Has been repaired, and repainted. FREE
>
> MAST 2" diameter steel mast, 9 feet long. Thick wall heavy duty galvanized
> steel. heavy
> mast.
>
> AS25G rotator plate also available for $20.00 - free if you take all three
> items above!
>
> Contact me off the list please.
>
> Bry Carling, AF4K
>
>
>
>
> ------------------------------
>
> Message: 8
> Date: Tue, 12 May 2015 16:12:48 -0400
> From: "Bry Carling AF4K" <bcarling at cfl.rr.com>
> To: Jon Pearl - W4ABC <jonpearl at tampabay.rr.com>, "Roger (K8RI) on TT"
> <K8RI-on-TowerTalk at tm.net>, <towertalk at contesting.com>, Scott Johns
> <scottw3tx at verizon.net>
> Subject: Re: [TowerTalk] Rohn towers
> Message-ID: <55525EC0.29361.444EAD at bcarling.cfl.rr.com>
> Content-Type: text/plain; charset=US-ASCII
>
> I have found a local surplus source for tubing that is well below the high
> retail prices at
> ALRO. These probably exist all over the country too...
>
> Bry AF4K
>
> On 11 May 2015 at 11:58, Scott Johns wrote:
>
>> One thing I have run in to with Arlo, which may be reflected in their
>> lower pricing, is Foreign alloy. Some of the foreign alloy has been
>> different enough in sizing that the 0.58 sections will not telescope. I
>> have not run into that problem with US alloy.
>>
>> 73, Scott W3TX
>>
>> On 5/11/15 11:51 AM, "Jon Pearl - W4ABC" <jonpearl at tampabay.rr.com>
>> wrote:
>>
>> >Hi Roger,
>> >
>> >
>> >
>> >I've found them very easy to work with when purchasing DOM tubing as
>> >well as aluminum plate. They'll even cut plate to dimensions for a few
>> >bucks per cut.
>> >
>> >
>> >
>> >
>> >
>> >73,
>> >
>> >
>> >Jon Pearl - W4ABC
>> >www.w4abc.com
>> >
>> >
>> >
>> >On 5/10/2015 8:10 PM, Roger (K8RI) on TT wrote:
>> >> On 5/10/2015 2:54 PM, Jon Pearl - W4ABC wrote:
>> >>> Orlando is right around the corner from you...
>> >>>
>> >>> http://www.alro.com/locations/locationsmain.aspx?Loc=FL
>> >>>
>> >>>
>> >> Standard disclaimer: I have no interest in Alro other than being a
>> >> satisfied customer
>> >>
>> >> I didn't realize they were so wide spread, but Alro has an outlet
>> >> about 20 miles from me up here in Michigan.Their prices, up here are
>> >> better than the local supply. Although I may purchase 10 stock
>> >> lengths of 1.5" and 2" diameter 6061T6 and DOM steel tube, at times I
>> >> have called over with a relatively small order that I had planned on
>> >> picking up. They delivered it right to my door. A small order is not
>> >> just one piece of mast. I assume they must have had another, larger
>> >> delivery in the area.
>> >>
>> >> As with large companies with multiple outlets, I assume policies may
>> >> vary between outlets.
>> >>
>> >> 73
>> >>
>> >> Roger (K8RI)
>> >>
>> >
>> >
>> >---
>> >This email has been checked for viruses by Avast antivirus software.
>> >http://www.avast.com
>> >
>> >_______________________________________________
>> >
>> >
>> >
>> >_______________________________________________
>> >TowerTalk mailing list
>> >TowerTalk at contesting.com
>> >http://lists.contesting.com/mailman/listinfo/towertalk
>>
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
>
> ------------------------------
>
> Message: 9
> Date: Tue, 12 May 2015 16:14:01 -0400
> From: "Bry Carling AF4K" <bcarling at cfl.rr.com>
> To: towertalk at contesting.com, Hans Hammarquist
> <hanslg at aol.com>
> Subject: Re: [TowerTalk] Current Choke for Ladder Line
> Message-ID: <55525F09.10586.456AE3 at bcarling.cfl.rr.com>
> Content-Type: text/plain; charset=US-ASCII
>
> I would think that the OCF is FAR more likely to radiate off the feedline
> than a conventional
> dipole in most circumstances.
>
> On 12 May 2015 at 14:01, Hans Hammarquist via TowerTal wrote:
>
>> Gentlemen,
>>
>>
>> I have seen many articles how to build and/or buy common mode chokes for
>> coax cables but I don't remember any articles how to build (or buy) and
>> choke for a 400 ohm ladder line.
>>
>>
>> The common mode current on a ladder line is causing the same problem as a
>> common mode current on a coax. i have a choke between my tuner and radio
>> which reduced noise quite good but wonder now how much RF power I radiate
>> and signal I receive from the CM current in the feeder to my OCF dipole.
>>
>>
>> Any ideas/comments?
>>
>> Hans - N2JFS
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
>
> ------------------------------
>
> Message: 10
> Date: Tue, 12 May 2015 16:15:26 -0400
> From: "Bry Carling AF4K" <bcarling at cfl.rr.com>
> To: towertalk at contesting.com, jim at audiosystemsgroup.com
> Subject: Re: [TowerTalk] Current Choke for Ladder Line
> Message-ID: <55525F5E.22027.46B710 at bcarling.cfl.rr.com>
> Content-Type: text/plain; charset=US-ASCII
>
> ... or just simplify things and use COAX feeders!
>
> Frankly I have never got along well with open wire feeders.
>
> Bry
>
> On 12 May 2015 at 11:28, Jim Brown wrote:
>
>> On Tue,5/12/2015 11:01 AM, Hans Hammarquist via TowerTalk wrote:
>> > Gentlemen,
>> >
>> >
>> > I have seen many articles how to build and/or buy common mode chokes
>> > for coax cables but I don't remember any articles how to build (or buy)
>> > and choke for a 400 ohm ladder line.
>>
>> That's because no one has thought of one that works. An important
>> component of the problem is that the Zo of practical two-wire chokes
>> wound on ferrite toroids is much lower than 400 Ohms. For example,
>> close-spaced enameled wire yields about 50 ohms, close-spaced THHN
>> (house wire) yields about 90 ohms.
>>
>> Another important component of the problem is that, because the
>> feedpoint is off-center, the common mode voltage gets VERY high if
>> you're running much power, so the dissipation in the choke is likely to
>> fry it.
>>
>> A third reason is the concentrated differential mode dissipation in the
>> turns of line when the antenna is poorly matched to the line.
>>
>> > The common mode current on a ladder line is causing the same problem as
>> > a common mode current on a coax.
>>
>> Exactly right.
>>
>> > i have a choke between my tuner and radio which reduced noise quite
>> > good but wonder now how much RF power I radiate and signal I receive
>> > from the CM current in the feeder to my OCF dipole.
>>
>> The only other practical way to kill common mode on high Z line would be
>> with a conventional 2-winding transformer capable of handling the power.
>> Fair-Rite #61 might be good enough for moderate power levels below about
>> 12 MHz, but its losses increase above that frequency. Fair-Rite #67
>> would be a better candidate -- its losses remain quite low up to about
>> 40 MHz, and are not bad at 50 MHz. On the graphs below, u's is the mu
>> that defines inductance, and u''s is the loss component in a series
>> equivalent circuit.
>>
>> http://www.fair-rite.com/newfair/materials61.htm
>>
>> http://www.fair-rite.com/newfair/materials67.htm
>>
>> http://www.fair-rite.com/cgibin/catalog.pgm?THEAPPL=Inductive+Components&THEWHERE=Closed+Magnetic+Circuit&THEPART=Toroids#select:freq1
>>
>> 73, Jim K9YC
>>
>> _______________________________________________
>>
>>
>>
>> _______________________________________________
>> TowerTalk mailing list
>> TowerTalk at contesting.com
>> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
>
>
> ------------------------------
>
> Subject: Digest Footer
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk at contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
> ------------------------------
>
> End of TowerTalk Digest, Vol 149, Issue 22
> ******************************************
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