1.1 Isolation Current Balun Q?

[N4NDX]

I'm in the process of building a 12/17 Dual Beam 2-El.-Open-Sleeve-Yagi which can be found here. http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=23310

The Isolation Current Balun showing is the W1JR Current Balun with a Amidon FT-140-66 ferrite core which is no longer available by Amidon. I know sometimes is easier to go and buy one but since I'm home brewing the Beam I want it all to be home brew. Any suggestions of which ferrite core to use and turns "(capable for legal limit)"

David/n4ndx

[W6EM]

David:  Amidon has a kit, consisting of an FT240-61, 2.4 inch diameter core and 12 ft of AWG 14 enameled copper.  Mix 61 ferrite is a good choice for HF applications.  They rate the kit for 1kW.  Price is $12.  http://www.amidoncorp.com/ab240-125-kit/  6 feet of bifilar-wound wire on the core should be more than enough for a dozen turns or so, which should give you enough reactance to make the current balun work properly.

You might want to get some 3M type 27 or 69 fiberglass high temperature electrical tape to wrap the core with before you wind it.  It helps protect the enamel wire insulation from getting scratched by the bare ferrite core when you wind it.  Most motor rewind shops have it and would probably sell you a few feet of it.

73,

Lee

[N4NDX]

Thanks Lee for your response. I've seen the kit by Amidon but I still want to be able to use 1.5 K if I needed to, not that I do it all the time but pile-ups some times gets hard to brake in to and that little extra kick comes in handy. HiHi

Thanks

[AC2EU]

Thanks Lee for your response. I've seen the kit by Amidon but I still want to be able to use 1.5 K if I needed to, not that I do it all the time but pile-ups some times gets hard to brake in to and that little extra kick comes in handy. HiHi

Thanks

You could always stack two toroids if you can't find one that will handle the flux...

[W6EM]

Thanks Lee for your response. I've seen the kit by Amidon but I still want to be able to use 1.5 K if I needed to, not that I do it all the time but pile-ups some times gets hard to brake in to and that little extra kick comes in handy. HiHi

Thanks

You could always stack two toroids if you can't find one that will handle the flux...

Good point.  And, the tape would come in handy, keeping them together while trying to wind two stacked cores.  Kits and Parts has the same cores for $10 each.  http://www.kitsandparts.com/toroids.php

[G3TXQ]

Stack two FT240-52 cores and wind with 10 turns of RG400 coax:
http://www.karinya.net/g3txq/chokes/

73,
Steve G3TXQ

[WA3SKN]

One FT240 core is OK for 1 KW under ideal conditions.
Two cores should give you an OK margin for 1.5 KW.
Many of the "heavy duty" baluns are being built with 3 cores... probably overkill for most needs.  Choice of mix depends on frequencies planned.
Good luck with the project.
73s.

-Mike

[W6EM]

Stack two FT240-52 cores and wind with 10 turns of RG400 coax:
http://www.karinya.net/g3txq/chokes/

73,
Steve G3TXQ

Steve:  Not familiar with mix 52.  Is it similar to 61, or more like 43?

Lee
W6EM

[G3TXQ]

Steve:  Not familiar with mix 52.  Is it similar to 61, or more like 43?

It has a permeability between #61 and #43, and as you'll see from my chart works really well in the mid to upper HF region. I bought mine from Mouser.

Mouser part number: 623-5952003801
Fair-Rite part number: 5952003801

73,
Steve

[N4NDX]

Hi Steve
Is this for a single or double stacked toroids?

73 David

[G3TXQ]

Is this for a single or double stacked toroids?

Line 11 on my chart:
http://www.karinya.net/g3txq/chokes/
is for two stacked cores.

It provides >8k choking impedance over a wide frequency range. Using two cores gives the OP some headroom when running 1.5kW.

73,
Steve G3TXQ

[N4NDX]

It sounds like a winner Steve, I'm gonna give it a shot

I appreciate the help.

73 de David/N4NDX

[N4NDX]

Hi Steve/G3TXQ

I've tried to find the FT240-52 core but is nearly impossible to find. I Visit Mouser on their Website and they have a 3 weeks waiting period for the core. Is there any other solution?


73 David

[G3TXQ]

Interesting - it's not often that FairRite cores are available in UK but not in the US! 8 turns of RG400 on two stacked FT240-61 cores is a reasonable alternative.

73,
Steve G3TXQ

[N4NDX]

I'm not giving up just yet, but just in case I get tire of looking I'll take that into consideration.

Thanks again

73 de David/n4ndx