[RFI] Bulk order source for Ferrite beads?

[Larry Benko]

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 at 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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