Couldn't agree with you more, Larry. 43 and 61 material is my choices for
CM chokes at HF as well. Those I presently have in the system are wound on
43 material.
Dave - WØLEV
On Sun, Feb 3, 2019 at 3:06 PM Larry Benko <xxw0qe@comcast.net> wrote:
> Jim,
>
> I respectfully disagree with your comment about 61 material cores not
> being useful at HF. For transmitting applications they are quite
> valuable. The low Q impedance provided by 31 materials is the go to
> solution for receiving applications but at high power care must be taken
> to ensure that the impedance is much higher than needed to keep the 31
> material from overheating. This is made even more difficult since the
> common mode impedance in a circuit is unrelated to the differential mode
> impedance and calculating what common mode current might flow through
> the common mode choke is not easy to do. Of course you can sneak up on
> the problem by just making the choke and slowly increasing the power at
> all frequencies you use and see if it gets too hot in your application.
> Not very scientific but common mode circuits are elusive to understand
> and simulate.
>
> Larry, W0QE
>
> On 2/2/2019 3:30 PM, Jim Brown wrote:
> > I also recommend Arrow, both for cost and service, especially for
> > small quantity. It helps a lot that shipping is free for an order of
> > $20 or more -- IF it's a web order for what's in stock. I also got a
> > very good price on 100 pieces of the 2.4-in o.d. #31 toroids. Other
> > good vendors are Lodestone Pacific, Dexter Magnetics, and the usual
> > industrial electronics houses like Newark, Allied, Mouser, etc.
> >
> > Note also that there is currently a tariff on these parts, which are
> > made in Fair-Rite's factory in China.
> >
> > BUT -- #61 cores are NOT of much use for RFI suppression below UHF,
> > and they are a terrible choice for a common mode choke (often called a
> > "current balun").
> >
> > 73, Jim K9YC
> >
> > On 2/2/2019 9:04 AM, Tom WA9WSJ via RFI wrote:
> >> Hi John,
> >> I once bought some big cores from these guys,
> >> https://www.jpmsupply.com
> >>
> >> (FT140-61 ferrites). At that time, a little over a year ago, they
> >> were the best prices I could find.
> >> They do have a couple other types. Maybe they can help you.
> >> Good luck!
> >> 73 Tom
> >>
> >>
> >>
> >> On Saturday, February 2, 2019, 9:26:14 AM MST, John Altman
> >> <wa4aip@gmail.com> wrote:
> >> Which company is the best source for bulk bead orders?
> >>
> >> Tks,
> >> John
> >> WA4AIP
> >> ARRL Charter Life Member
> >>
> >>
> >> Sent from my iPad PRO
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> >
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--
*Dave - WØLEV*
*Just Let Darwin Work*
*Just Think*
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