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toroids for vhf comms aerial cable

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rowlandcarson(at)gmail.co
Guest

Posted: Fri Sep 20, 2013 12:41 am Post subject: toroids for vhf comms aerial cable

Annex C of my manual calls out 4-off toroids to fit on the RG-58 coax cable adjacent to the dipole tapes. The part number given is Philips 4330 030 34420, but this now appears to be made of unobtainium.



Does anyone know of an equivalent ferric toroid currently available?



RS list hundreds; obviously it needs to have a central hole of a suitable size for RG-58 (or probably RG-400 in my case) to pass through, but what about the other dimensions, and the magnetic characteristics? It's not clear whether the toroids are fitted to act as a filter, as tuning, or as a balun. If, as I suspect, the latter, the magnetic characteristics are likely to be more critical.



in friendship



Rowland

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frans(at)privatepilots.nl
Guest

Posted: Fri Sep 20, 2013 1:23 am Post subject: toroids for vhf comms aerial cable

On 09/20/2013 10:34 AM, Rowland Carson wrote:

 	  Quote: 	
		   


	


 	  Quote: 	
		   RS list hundreds; obviously it needs to have a central hole of a suitable size for RG-58 (or probably RG-400 in my case) to pass through, but what about the other dimensions, and the magnetic characteristics? It's not clear whether the toroids are fitted to act as a filter, as tuning, or as a balun. If, as I suspect, the latter, the magnetic characteristics are likely to be more critical.


	


The torroids are there do make it clear to the electrons where the

border is between the outer surface of the coax and the antenna leg

connected to it. Without the torroids it is just one long piece of

conductor.

It is not that critical though, but without these torroids you will get

more radiation from the cable itself and it will pick up more noise from

the surroundings of the cable, and since this is an airplane packed with

lots of electronic stuff you will want to prevent that.

The magnetic properties of the torroids are critical indeed. I don't

have a list or manual, part numbers have been disappeared from memory

long time ago, but you obviously need to find something suitable for the

intended frequency range (100-150 MHz). Some googling is in order here.

Or ask a local radio amateur club, the popular 2m-band (144 MHz) is

close to the aircraft frequencies and what will work for them will work

for you too. Changes are that someone has a box full of these things on

his bench and is happy to share a few.



As an alternative you can coil up a part of the coax close to the

antenna, but this is heavier.



Frans

carl(at)flyers.freeserve.
Guest

Posted: Fri Sep 20, 2013 1:37 am Post subject: toroids for vhf comms aerial cable

As I recall Rowland, any old toroid is suitable. I think we used ones

sourced from Maplin or Tandy and they appear to work fine.



Being a non-technical type I haven't got an idea if the exact specification

was critical.



--

grahamsingleton(at)btinte
Guest

Posted: Fri Sep 20, 2013 1:43 am Post subject: toroids for vhf comms aerial cable

Rowland

they are to form a balun, Fergus Kyle will probably know the answers you want,

he won't be up yet (Ontario)

Graham



        From: Frans Veldman <frans(at)privatepilots.nl>

 To: europa-list(at)matronics.com 

 Sent: Friday, 20 September 2013, 10:23

 Subject: Re: toroids for vhf comms aerial cable

  

 

--> Europa-List  message posted by: Frans Veldman <frans(at)privatepilots.nl (frans(at)privatepilots.nl)>



On 09/20/2013 10:34 AM, Rowland Carson wrote:

 	  Quote: 	
		   --> Europa-List message posted by: Rowland Carson <rowlandcarson(at)gmail.com (rowlandcarson(at)gmail.com)>


	


 	  Quote: 	
		   RS list hundreds; obviously it needs to have a central hole of a suitable size for RG-58 (or probably RG-400 in my case) to pass through, but what about the other dimensions, and the magnetic characteristics? It's not clear whether the toroids are fitted to act as a filter, as tuning, or as a balun. If, as I suspect, the latter, the magnetic characteristics are likely to be more critical.


	


The torroids are there do make it clear to the electrons where the

border is between the outer surface of the coax and the antenna leg

connected to it. Without the  torroids it is just one long piece of

conductor.

It is not that critical though, but without these torroids you will get

more radiation from the cable itself and it will pick up more noise from

the surroundings of the cable, and since this is an airplane packed with

lots of electronic stuff you will want to prevent that.

The magnetic properties of the torroids are critical indeed. I don't

have a list or manual, part numbers have been disappeared from memory

long time ago, but you obviously need to find something suitable for the

intended frequency range (100-150 MHz). Some googling is in order here.

Or ask a local radio amateur club, the popular 2m-band (144 MHz) is

close to the aircraft frequencies and what will work for them will work

for you too. Changes are that someone has a box full of these things on

his bench and is happy to share a few.



As an alternative you can coil up a part of the coax close to "http://www.matronics.com/Navigator?Europa-List" target="_blank">http://w.com/" =   -->  [quote][b]

Fred Klein

Joined: 26 Mar 2012
Posts: 503

Posted: Sat Sep 21, 2013 9:15 am Post subject: toroids for vhf comms aerial cable

I have one of those AAE dipole antennas...there is no mention in the installation instructions of adding toroids or the need thereof...am I missing something?



Fred



On Sep 20, 2013, at 2:42 AM, GRAHAM SINGLETON wrote:

[quote]Rowland

they are to form a balun, Fergus Kyle will probably know the answers you want,

he won't be up yet (Ontario)

Graham



[b]

Martymason

Joined: 17 Apr 2009
Posts: 20
Location: Norcross, GA

Posted: Sat Sep 21, 2013 9:48 am Post subject: Re: toroids for vhf comms aerial cable

Rowland make a coaxial cable balun per Lectric Bob's instructions at http://www.aeroelectric.com/articles/BALUN/Balun_Fabrication .

For a comm antenna the lengths should be 59 cm or 23.25 inches vs. 26 inches. The RG400 cable solders easily and will not melt.



Marty

_________________
Marty Mason
Norcross, GA

Martymason

Joined: 17 Apr 2009
Posts: 20
Location: Norcross, GA

Posted: Sat Sep 21, 2013 9:54 am Post subject: Re: toroids for vhf comms aerial cable

OOps, the correct article is 



http://www.aeroelectric.com/articles/BALUN/Balun_Fabrication.html



Marty

_________________
Marty Mason
Norcross, GA

tonyvaccarella

Joined: 10 Sep 2014
Posts: 68
Location: Australia

Posted: Wed Oct 08, 2014 4:18 pm Post subject: Re: toroids for vhf comms aerial cable

Hi Europa members,



I realise this thread is a year old but I just came across the same problem in trying to find the Philips Toroids P/N 4330 030 34420 that were recommended in the VHF Antenna build manual. You will need four of these for the VHF antenna construction.



I'm fortunate because I work for a major Avionics company here in Sydney Australia and I had the Chief Engineer look at the specs for these toroids and he advised that you cant just use any old toroid - as suggested by someone in this thread. They all are manufactured for different frequencies and applications. One other piece of advice he offered is that if you are using copper tape to make the antenna, use the widest tape that you can find as this provides better performance over the entire VHF spectrum 118 - 136Mhz. In other words if you used thin tape, you will only have best performance at the mid-frequency but not so great at either end of the spectrum. 



The first number in the Philips toroid P/N "4" refers to the "mix" in the ferrite. It is suitable for VHF at 100MHz. He found a suitable replacement that had an inside diameter is 5.4mm that  will slip over RG400 (4.9mm) safely. 



You can buy then in a pack of 10 from RS Components. In Sydney I can buy them for about $15 (including delivery). 



check  http://au.rs-online.com/web/p/ferrite-rings/1741229/



I hope this helps.



Regards,

Tony Vaccarella

_________________
Tony Vaccarella
Mascot NSW 2020
Sydney Australia

tonyvaccarella

Joined: 10 Sep 2014
Posts: 68
Location: Australia

Posted: Wed Oct 08, 2014 4:24 pm Post subject: Re: toroids for vhf comms aerial cable

Hi again,



I forgot to mention that you SHOULD NOT use a balun for VHF antenna construction as suggested by "Martymason". I have been advised that the balun will pass all the transmit energy to and from the entire length of the co-axial cable. This is what you DONT want from a transmit antenna and can damage your radio. 



Baluns are used for receive antennas e.g. VOR antennas.



Bye all



Tony

_________________
Tony Vaccarella
Mascot NSW 2020
Sydney Australia

rampil

Joined: 04 May 2007
Posts: 870

Posted: Fri Oct 10, 2014 2:26 am Post subject: Re: toroids for vhf comms aerial cable

Just a quick note from a former electrical engineer:

While its true that ferrites are made from a variety 

of materials, and in a variety of sizes, the actual 

specs are NOT critical.  A ferrite that fits over 

whichever coax you are using and is designed

for VHF frequency work will work fine.



This isn't rocket science 

The ARRL Handbook is a great reference for this subject,

and Bob Nuckolls also has information on the topic on

his web site.

_________________
Ira N224XS

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