Matronics Email Lists :: View topic

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

Toroid beads

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

berkut13(at)berkut13.com
Guest

Posted: Fri Oct 24, 2014 9:04 am Post subject: Toroid beads

Anyone got a part number (or  spec) handy for the toroid beads that slide over the RG-58/400 coax on our home  made antennas?



  -James



   [quote][b]

tim2542(at)sbcglobal.net
Guest

Posted: Fri Oct 24, 2014 9:41 am Post subject: Toroid beads

If you dont find any James let me know, I have a few left over.

Tim Andres

 

     On Friday, October 24, 2014 10:23 AM,  "berkut13(at)berkut13.com" <berkut13(at)berkut13.com> wrote:

  

  



      Anyone got a part number (or  spec) handy for the toroid beads that slide over the RG-58/400 coax on our home  made antennas?



  -James



   [quote]

[b]

deej(at)deej.net
Guest

Posted: Fri Oct 24, 2014 9:54 am Post subject: Toroid beads

On 10/24/2014 01:03 PM, berkut13(at)berkut13.com wrote:

 	  Quote: 	
		   *Anyone got a part number (or spec) handy for the toroid beads that

 slide over the RG-58/400 coax on our home made antennas?*


	




Radio Shack sells them (called Snap Choke Core):



http://www.radioshack.com/family/index.jsp?categoryId 32273&znt_campaign=Category_CMS&znt_medium=RSCOM&znt_source=CAT&znt_content=CT2032230



-Dj

-- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

berkut13(at)berkut13.com
Guest

Posted: Fri Oct 24, 2014 9:56 am Post subject: Toroid beads

Will need them ongoing, I was really looking for a source.

  

 Thanks though.

 -James

    

  From: Tim Andres (tim2542(at)sbcglobal.net) 

 Sent: Friday, October 24, 2014 12:37 PM

 To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)  

 Subject: Re: Toroid beads

  



   If you dont find any James let me know, I have a few left  over.

 Tim  Andres

 

    On Friday, October 24, 2014 10:23 AM,  "berkut13(at)berkut13.com" <berkut13(at)berkut13.com>  wrote:



       Anyone got a part number (or  spec) handy for the toroid beads that slide over the RG-58/400 coax on our home  made antennas?



  -James



[quote]





href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-List

href="http://forums.matronics.com">http://forums.matronics.com

href="http://www.matronics.com/contribution">http://www.matronics.com/c

[b]

berkut13(at)berkut13.com
Guest

Posted: Fri Oct 24, 2014 10:21 am Post subject: Toroid beads

Too big.  Looking for source for the small ferrite "doughnuts" that  slip over the coax at the di-pole element split.

  

 Shown here:

 http://www.berkut13.com/com2_08.jpg

  

 Thanks,

 James

  

  

  

  

 --

jimkale(at)roadrunner.com
Guest

Posted: Fri Oct 24, 2014 10:32 am Post subject: Toroid beads

You might try RST Engineering.  It is the guy who writes the Kit Planes Electronics articles.  He normally sells them.

From: owner-aeroelectric-list-server(at)matronics.com [mailto:owner-aeroelectric-list-server(at)matronics.com] On Behalf Of berkut13(at)berkut13.com

Sent: Friday, October 24, 2014 12:55 PM

To: aeroelectric-list(at)matronics.com

Subject: Re: Toroid beads

Will need them ongoing, I was really looking for a source.

Thanks though.

-James

From: Tim Andres (tim2542(at)sbcglobal.net) 

Sent: Friday, October 24, 2014 12:37 PM

To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com) 

Subject: Re: Toroid beads

If you dont find any James let me know, I have a few left over.

Tim Andres

On Friday, October 24, 2014 10:23 AM, "berkut13(at)berkut13.com (berkut13(at)berkut13.com)" <berkut13(at)berkut13.com (berkut13(at)berkut13.com)> wrote:

Anyone got a part number (or spec) handy for the toroid beads that slide over the RG-58/400 coax on our home made antennas?

-James

 	  Quote: 	

 	  Quote: 	
		    href="http://www.matronics.com/Navigator?AeroElectric-List">http://www.matronics.com/Navigator?AeroElectric-Listhref="http://forums.matronics.com">http://forums.matronics.comhref="http://www.matronics.com/contribution">http://www.matronics.com/c   	
0 	  Quote: 	

1 	  Quote: 	

2 	  Quote: 	

3 	  Quote: 	

4 	  Quote: 	

5 	  Quote: 	

6 	  Quote: 	

7 	  Quote: 	

8 	  Quote: 	

9 	  Quote: 	

0 	  Quote: 	

1 	  Quote: 	

2 	  Quote: 	

3 	  Quote: 	

4 	  Quote: 	

5

   [quote][b]

deej(at)deej.net
Guest

Posted: Fri Oct 24, 2014 10:41 am Post subject: Toroid beads

On 10/24/2014 02:19 PM, berkut13(at)berkut13.com wrote:

 	  Quote: 	
		   Too big.  Looking for source for the small ferrite "doughnuts" that slip

 over the coax at the di-pole element split.

  

 Shown here:

 http://www.berkut13.com/com2_08.jpg


	


Hi James, I think the ones from Radio Shack will perform the same job,

electrically.



Yes, they are physically bigger, but they do offer one that is the right

inside diameter size to fit around the coax.  They just have a plastic

case around the ferrite that "snaps" in place.  Makes them easy to

remove, too, without having to undo any soldering or crimping since they

are a split configuration.



You can remove the outer plastic shell and wrap them with something

smaller (tape, whatever) if the physical outside diameter is too big.



You can probably find the exact ones you are looking for at McMaster

Carr or some other online source, and someone else on the list might be

able to offer a specific reference.



-Dj

-- 

Dj Merrill - N1JOV - VP EAA Chapter 87

Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

Glastar Flyer N866RH - http://deej.net/glastar/

berkut13(at)berkut13.com
Guest

Posted: Fri Oct 24, 2014 11:10 am Post subject: Toroid beads

No thanks!  Last time I ordered from RST, it took 6 months of reminder  phone calls/emails to get it.  Iâ€™m not ever doing that again...YMMV.

  

 To keep this on track...I need specs and a distributor if possible.   

 http://www.mouser.com/catalog/catalogusd/647/1295.pdf

  

 If the selection is nothing more than finding something that fits around  the coax, I would order from the â€œTOROIDAL FERRITE BEADSâ€ section.

  

 -James

    

  From: Jim Kale (jimkale(at)roadrunner.com) 

 Sent: Friday, October 24, 2014 1:32 PM

 To: aeroelectric-list(at)matronics.com (aeroelectric-list(at)matronics.com)  

 Subject: RE: Toroid beads

  



   

You  might try RST Engineering.  It is the guy who writes the Kit Planes  Electronics articles.  He normally sells them. 

 



   [quote][b]

tim2542(at)sbcglobal.net
Guest

Posted: Fri Oct 24, 2014 11:19 am Post subject: Toroid beads

Those are much different than the ones I think James May be looking for. I have no idea if they are suitable. RST once sold a kit with the small ferrite beads that just fit the RG 58 and could easily be imbedded into a composite structure. I think that is what he's looking for. 

Tim



 	  Quote: 	
		   On Oct 24, 2014, at 10:53 AM, Dj Merrill <deej(at)deej.net> wrote:

 

 

 

> On 10/24/2014 01:03 PM, berkut13(at)berkut13.com wrote:

> *Anyone got a part number (or spec) handy for the toroid beads that

> slide over the RG-58/400 coax on our home made antennas?*

 

 

 Radio Shack sells them (called Snap Choke Core):

 

 http://www.radioshack.com/family/index.jsp?categoryId 32273&znt_campaign=Category_CMS&znt_medium=RSCOM&znt_source=CAT&znt_content=CT2032230

 

 -Dj

 

 

 -- 

 Dj Merrill - N1JOV - VP EAA Chapter 87

 Sportsman 2+2 Builder #7118 N421DJ - http://deej.net/sportsman/

 Glastar Flyer N866RH - http://deej.net/glastar/

ralphmariafinch(at)gmail.
Guest

Posted: Fri Oct 24, 2014 11:21 am Post subject: Toroid beads

Or your mileage won't vary. I keep seeing bitter complaints about RST total lack of customer service. I'd for sure never order anything from him.



On Fri, Oct 24, 2014 at 12:08 PM,  <berkut13(at)berkut13.com (berkut13(at)berkut13.com)> wrote:

[quote]        No thanks!  Last time I ordered from RST, it took 6 months of reminder  phone calls/emails to get it.  I&rsquo;m not ever doing that again...YMMV.

 

[b]

wrmaxwell(at)bigpond.com
Guest

Posted: Fri Oct 24, 2014 2:15 pm Post subject: Toroid beads

They are simply called         "toroids", which describe their shape, Jim. They come in various         compositions, both ferite and iron, that vary in their frequency         responses. You will need need a       ferite composition effective at VHF.  Commonly       available through ham radio suppliers, so should not be too hard       to find over there.

     

     Bill

     

     On 25/10/2014 5:19 AM,       berkut13(at)berkut13.com (berkut13(at)berkut13.com) wrote:

     

     [quote]                           Too big.  Looking for source for the small ferrite             "doughnuts" that slip over the coax at the di-pole element             split.

            

           Shown here:

           http://www.berkut13.com/com2_08.jpg

            

           Thanks,

           James

            

            

            

            

           --

nuckolls.bob(at)aeroelect
Guest

Posted: Fri Oct 24, 2014 7:22 pm Post subject: Toroid beads

At 12:03 PM 10/24/2014, you wrote:

  	  Quote: 	
		   Anyone got a part number (or spec) handy for the toroid beads that slide over the RG-58/400 coax on our home made antennas?

 -James 	


   These are so ineffectual as to make their 'benefits'

   undetectable except by sophisticated test equipment

   in the lab.  Cessna produced thousands of airplanes with

   coax brazenly attached to horizontal cat-whisker dipoles

   with excellent results.  Our resident physics PhD did a study

   on these antennas back in '69 or so. This was before 'donuts

   on the coax' became the 'buzz-phrase'. Back then the purists

   were into 4:1 coax baluns . . . they took care of the 'worries'

   about feeding an unbalanced coax with a balanced antenna  . . .

   but demonstrated a 3:1 SWR under the best condition. 



   Later, somebody tried the ferrite beads thing . . . not all

   ferrites are made the same. You need a material that

   exhibits low losses at the frequency of interest . . . 110

   Mhz or thereabouts. Then it's useful to understand that

   the EFFECTIVENESS of adding such magnetics to the feed line

   varies as the SQUARE of the turns. So, 9 ferrites strung

   along a coax offer performance on the order of three turns

   of coax fed through a larger torroid.



   The big question is: If you don't have a balun (coax

   or ferrite), who would know? The answer is: nobody.

   We're talking a receiving antenna excited with nano or

   pico watts from a ground station. Further, the signal

   is line of sight . . . seldom more than 50 miles from

   ground station to airplane. A wet string with a gazillion

   to one SWR would receive the signal.



   If you'd really like to 'balance' things up, you

   can build a 1:1 "Pawsey stub" balun from a piece of

   scrap coax.  See:



  http://tinyurl.com/yytxwd3



   I've built dozens of these and the work just fine

   but as a VOR receive antenna, the benefits for having

   installed it are not observable from the cockpit.



   If you'd like to see an example of effective

   ferrite decoupling of a badly mated antenna/feedline

   condition, look at the "airwhip" vhf comm antenna

   articles on the web. One poster took one apart to show

   the ferrite torroid at the base with 4-5 turns of

   coax through the core . . . 16 to 25 times the

   effectiveness of a single core. Further, the material

   from which this core is made is narrowly crafted for

   the frequency of interest. Ferrites from Radio Shack

   for noise mitigation are not even close.



   My first choice: Hook the coax to the antenna 'bare

   foot' and it will work fine. 



   Second choice; Build a 1:1 Pawsey stub balun.



   Third choice; track down suitable torroids but use

   larger ones that will allow multiple passes of

   coax thorugh the center.



   But understand that choices 2 an 3 are pretty much

   a waste of time in terms of outcome.



 

   Bob . . .    [quote][b]

dlj04(at)josephson.com
Guest

Posted: Sat Oct 25, 2014 1:09 am Post subject: Toroid beads

I agree with Bob that ferrite donuts are not necessary or desirable for 

VOR/LOC/GS antennas. If you want good symmetrical coverage, you want a 

balanced feed for your dipole and the folded balun shown in Bob's



http://tinyurl.com/yytxwd3



is a good way to do that. The benefits are observable in the cockpit in 

the form of increased reception range for weak signals.



If you want to make a com antenna and it's tuned correctly but you want 

it to be a little more broadband (lower VSWR at the band edges,) using a 

string of ferrite toroids or a tubular ferrite core is one approach.



You are using the ferrites to create loss, not coupling. In effect you 

create a high resistance for currents flowing on the outside of the 

shield. It is partly resistance, not just impedance. If there is high 

VSWR, the ferrite heats up when you transmit, the same as a resistor in 

series would, allowing some of the reflected power to be dissipated as 

heat rather than bouncing back to the radio. This is not *exactly* what 

you want, but it's better than having the radio shut down if you try to 

transmit at 135 MHz and your antenna is sharply tuned to 122.



You do not want to create additional tuned circuits by looping the coax 

through one larger toroid, you just want to create resistive loss for 

reflected power, because you haven't designed an antenna that's 

inherently broadband enough (good broadband antennas don't need 

ferrites.) A suitable sleeve or tube core is Fair-Rite 2643625202, 

available from Mouser 

http://www.mouser.com/ProductDetail/Fair-Rite/2643625202 for about a 

dollar. This can substitute for the 3 or 4 donuts often used. You should 

use ferrites only when you can't get the VSWR low enough any other way.



--

David Josephson

thomas.n.gautier(at)jpl.n
Guest

Posted: Sat Oct 25, 2014 3:08 am Post subject: Toroid Beads

If you decide to go the bead route check out 

palomar-engineers.com

for a source of suppressor beads for coax. They have a nice application chart. 



Nick Gautier



Sent from my iPhone

nuckolls.bob(at)aeroelect
Guest

Posted: Sat Oct 25, 2014 7:21 am Post subject: Toroid beads

 	  Quote: 	
		  You do not want to create additional tuned circuits by looping the coax through one larger toroid, you just want to create resistive loss for reflected power, because you haven't designed an antenna that's inherently broadband enough (good broadband antennas don't need ferrites.) 	




   Agreed to within one important point. There are 'ferrites'

   and then there are 'FERRITES' . . . 



   There's a constellation of mixes of metal and binders used

   to fabricate the device. A ferrite core can be an

   efficient, compact solution to the fabrication of an

   inductor or transformer. In this instance, the manufacturer

   strives for the LOWEST possible losses in the core material

   at the frequency of interest.



   When used as a mitigator of noise, design goals can include

   a 'filter' comprised of combinations of inductors and capacitors

   that provide high series impedance (inductor) and low shunt

   impedance (capacitor) at the antagonistic frequencies. In this

   case, low loss components don't 'exterminate' the noise, they

   just 'contain' it.



   With the advances in powered metal technologies it was

   discovered that while putting a ferrite 'bead' or toroid

   over a wire would create a lumped inductance of some small

   value . . . the designer could, if goals warranted, include

   some material in the bead that made it a lousy candidate for

   tuned circuits or transformers. This material deliberately

   created energy losses within the core material . . . losses

   that converts antagonistic energies into heat thus reducing

   their nuisance factors.



  http://tinyurl.com/3b7nuj



   As a general rule, ALL products sold for the purposes

   of reducing noise will be fabricated from materials having

   deliberate losses . . . like the filter 'beads' and

   'snap around the cable' products.



   But when you pick up one of those little donut shaped

   thingies with no particularly defining features of

   color or part numbers, you're in the dark.  The

   odd toroid captured in the wild is often optimized

   for a rather narrow range of characteristics that

   may or may not be suited to your task.



   One of several resources for reviewing capabilities

   and limits for the various products can be found

   here . . .



  http://tinyurl.com/nx4qb9h



   In the case for the 'string of beads on the coax'

   the goal is to de-couple currents flowing on the

   feed line shield, the task is not to add a filtering

   loss but to add a high-q (read low loss) common mode

   inductance to the feed-line. This would become the

   lumped component version of a Pawsey stub or Bazooka

   balun.



   As far as weak signal performance goes, the only

   time you're even close to experiencing a 'weak signal'

   event is trying to read a VOR radial that is WWAAAaaayy

   off the beaten track for IFR operations.



   When "flying the routes", your charts will be marked

   with a VOR change-over point . . . a location along

   a line between VOR stations that is "equal signal"

   for the stations of interest. For this mode of flight ops,

   signal strengths combined with modern receiver 

   capabilities make a 'weak signal' event due to

   standing waves on your feed line a physical

   impossibility.



   I've played with 'beads on the coax' in the lab and

   found their benefit to be difficult to measure with

   boxes having names like Hewlett-Packard and Watkins-

   Johnson on them. The notion that you're going to

   get more meaningful measurements with a box having

   Garmin or King on front is not grounded in practice.



 A suitable sleeve or tube core is Fair-Rite 2643625202, available from Mouser  http://www.mouser.com/ProductDetail/Fair-Rite/2643625202 for about a dollar. This can substitute for the 3 or 4 donuts often used. You should use ferrites only when you can't get the VSWR low enough any other way.



 

   Not very quantified . . . who actually measures VSWR

   on a VOR antenna and what is 'low enough'? The measure

   of antenna performance cannot be lumped into the VSWR

   bucket. A resistor can have a VSWR of 1:1 over a huge

   range of frequencies with ZERO performance while an

   antenna with 'low enough' VSWR can perform poorly for

   a variety of reasons not related to the antenna itself.



   Antenna science is a BIG PICTURE activity that has

   to included the entire sphere of interest . . . while

   centered on your headphones, the sphere envelopes a host of

   variables no single one of which is the holy grail

   of satisfactory operations.

   

   Consider some of the Blue Tooth, Wi-Fi and remote

   control products. Very few of these devices have

   antennas that would warm Bob Archer's heart . . . but

   in the context of their operating sphere, they

   perform as advertised. Some with pretty amazing

   results. Dr. Dee can wear her little Blue-Tooth ear

   piece and be out weeding in her garden while tutoring

   a student. Amazes me.



 

   Bob . . .    [quote][b]

dlj04(at)josephson.com
Guest

Posted: Sun Oct 26, 2014 10:02 am Post subject: Toroid beads

The constellation of materials used to make ferrites is referred to as 

the "mix." Most common of the ferrites used in RF transformers and 

chokes at VHF is type 43, which is mostly nickel and zinc. It's useful 

over the whole com/nav/GS range, particularly if you are looking for 

loss as we are, rather than high-Q inductance. There is good information 

on the Palomar Engineers page referred to by Tom Gauthier. If you don't 

recognize the joke in the Palomar author's pseudonym (sadly, the man 

behind the name died at 90 last year after many excellent articles over 

the years), you haven't been around antennas long enough...



Many engineers who use ferrites don't really understand what's going on. 

Note that many manufacturers now specify the result of putting a core on 

a wire in terms of impedance rather than inductance. It is not as simple 

as a lumped inductance caused by increased permeability; if it were, the 

effect would not be so broadband. Refer to several papers by Jim Brown 

(and one by him and me, using a lot of H-P, W-J and Anritsu test 

equipment) on ferrites at www.audiosystemsgroup.com/publish.htm ... Jim 

and I started doing a lot of work analyzing the behavior of ferrites for 

rfi reduction in audio equipment and learned a lot of surprising stuff.



The core mentioned in my previous post (the URL got mangled, go to 

mouser.com and enter 2643625202) adds about 350 ohms of impedance, 

mostly resistive, to a single wire at 100 MHz.



I agree, there's no reason to use ferrites on a receiving antenna. As I 

mentioned, you use them only on a com antenna coax, where it attaches to 

the antenna, when the VSWR is too high. If your radio works without 

ferrites on the coax, leave them off, they are a band-aid to fix 

compromised antenna design. They will never make a bad antenna better, 

only allow a radio to work with a bad antenna when it might not 

otherwise. The heat generated in the ferrite is the power you would have 

radiated if the antenna had been properly matched. You want an actual 

balun such as a Pawsey stub or a hybrid transformer for a VOR antenna 

not to reduce VSWR, but to keep the pattern symmetrical. Not nice to 

receive a VOR when you're heading east and have it disappear when you 

turn west (I have had this experience while I was developing antennas on 

my Mooney, and it was fixed by using a balun.) And some of us do use 

VORs still.



David Josephson

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum