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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@contesting.com>
To: towertalk@contesting.com
Subject: [TowerTalk] Current Choke for Ladder Line
Message-ID: <14d4949e6e0-3e03-17f6e@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@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Current Choke for Ladder Line
Message-ID: <5552465D.5040304@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@cfl.rr.com>
To: Hans Hammarquist <hanslg@aol.com>
Cc: "towertalk@contesting.com" <towertalk@contesting.com>
Subject: Re: [TowerTalk] Current Choke for Ladder Line
Message-ID: <3C35924F-0625-4F3C-AF9C-098870B63ACE@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@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@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
------------------------------
Message: 4
Date: Tue, 12 May 2015 11:41:41 -0700
From: Jim Brown <jim@audiosystemsgroup.com>
To: towertalk@contesting.com
Subject: Re: [TowerTalk] Current Choke for Ladder Line
Message-ID: <55524965.20303@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@windstream.net>
To: towertalk@contesting.com
Subject: [TowerTalk] Mast inquiries
Message-ID: <55525312.8050000@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@tampabay.rr.com>
To: <towertalk@contesting.com>
Subject: [TowerTalk] Balun S Parameter
Message-ID: <C77F792FEA5F4E828EF7B4AADFAD608C@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@cfl.rr.com>
To: towertalk@contesting.com
Subject: [TowerTalk] FREE Tower parts in Central Florida
Message-ID: <55525D2B.30899.3E1FB1@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@cfl.rr.com>
To: Jon Pearl - W4ABC <jonpearl@tampabay.rr.com>, "Roger (K8RI) on TT"
<K8RI-on-TowerTalk@tm.net>, <towertalk@contesting.com>, Scott Johns
<scottw3tx@verizon.net>
Subject: Re: [TowerTalk] Rohn towers
Message-ID: <55525EC0.29361.444EAD@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@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@contesting.com
>http://lists.contesting.com/mailman/listinfo/towertalk
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------------------------------
Message: 9
Date: Tue, 12 May 2015 16:14:01 -0400
From: "Bry Carling AF4K" <bcarling@cfl.rr.com>
To: towertalk@contesting.com, Hans Hammarquist
<hanslg@aol.com>
Subject: Re: [TowerTalk] Current Choke for Ladder Line
Message-ID: <55525F09.10586.456AE3@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@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@cfl.rr.com>
To: towertalk@contesting.com, jim@audiosystemsgroup.com
Subject: Re: [TowerTalk] Current Choke for Ladder Line
Message-ID: <55525F5E.22027.46B710@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
_______________________________________________
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http://lists.contesting.com/mailman/listinfo/towertalk
------------------------------
Subject: Digest Footer
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------------------------------
End of TowerTalk Digest, Vol 149, Issue 22
******************************************