[RFI] RFI Digest, Vol 171, Issue 2

Sat Apr 15 17:14:40 EDT 2017

Re the Fair-Rite 2631814002, Arrow sells these in single unit quantities at $17.68 and has three in stock...maybe not for long!  Shipping is also free...a new practice for Arrow.  Arrow's prices have generally been considerable lower on Fair-Rite products than the other vendors I've searched, and if you register, you get a bit of a price break..

Mouser is showing 251 in stock with a single unit price of $18.09.
---
Chuck, AE4CW

-----Original Message-----
From: RFI [mailto:rfi-bounces at contesting.com] On Behalf Of rfi-request at contesting.com
Sent: Saturday, April 15, 2017 12:00:PM
To: rfi at contesting.com
Subject: RFI Digest, Vol 171, Issue 2

Send RFI mailing list submissions to
	rfi at contesting.com

To subscribe or unsubscribe via the World Wide Web, visit
	http://lists.contesting.com/mailman/listinfo/rfi
or, via email, send a message with subject or body 'help' to
	rfi-request at contesting.com

You can reach the person managing the list at
	rfi-owner at contesting.com

When replying, please edit your Subject line so it is more specific than "Re: Contents of RFI digest..."

Today's Topics:

   1. Re: New Larger Fair-Rite #31 Toroid (Jim Brown)
   2. Re: New Larger Fair-Rite #31 Toroid (Dave Cole)
   3. Re: New Larger Fair-Rite #31 Toroid (Jim Brown)
   4. Re: New Larger Fair-Rite #31 Toroid (Chuck Gooden)
   5. Re: New Larger Fair-Rite #31 Toroid (Jim Brown)
   6. Re: New Larger Fair-Rite #31 Toroid (Dave Cole)

----------------------------------------------------------------------

Message: 1
Date: Fri, 14 Apr 2017 09:53:09 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: rfi at contesting.com, towertalk reflector <towertalk at contesting.com>
Subject: Re: [RFI] New Larger Fair-Rite #31 Toroid
Message-ID:
	<ce55463f-e551-b656-9a4b-5ba271c8ec7a at audiosystemsgroup.com>
Content-Type: text/plain; charset=windows-1252; format=flowed

Yesterday, I got a quote on this part from Dexter, a vendor that has been competitive for past orders. They don't have stock, minimum order is a full box, which is 25 pieces, $15.18 each. 50 pieces is $14.27 (-6%). 100 pieces is $13.57. Delivery was quoted as 14 weeks.

73, Jim K9YC

On Sun,3/26/2017 4:22 PM, Jim Brown wrote:
> KY8D asked me about a new, larger #31 toroid that has recently been 
> added to the catalog. It's 4-in o.d., 3-in i.d, and 1-inch long.
>
> http://www.fair-rite.com/product/round-cable-emi-suppression-cores-263
> 1814002/
>
>
> Note the impedance data for 1, 3, and 5 turns at the bottom of the page.
>
> Gan's email arrived today (Sunday) so I haven't had the opportunity 
> yet to investigate pricing. My guess is at least double the cost of 
> the 2.4-in toroid, but because it's twice the length (1-in as opposed 
> to 0.5-in for the 2.4-in toroid), a single core will likely be 
> equivalent to two of the 2.4-in cores, so fewer cores will be required 
> to achieve the same choking Z. More important, the much larger i.d.
> will allow more turns and/or larger coax.
>
> 73, Jim K9YC
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>

------------------------------

Message: 2
Date: Fri, 14 Apr 2017 10:26:19 -0700
From: Dave Cole <dave at nk7z.net>
To: rfi at contesting.com
Subject: Re: [RFI] New Larger Fair-Rite #31 Toroid
Message-ID: <978afca3-90d0-2cb5-634b-90bab01defea at nk7z.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

Jim,

A question for you...  Looking at the "Impedance vs. Frequency vs. Turn count" graph at:

http://www.fair-rite.com/product/round-cable-emi-suppression-cores-2631814002/

It looks like these new cores only have two or three K of impedance with
  five turns...  Am I interpreting this correctly?

If so, then using two of them with five turns becomes the standard if I want more than five K impedance?  Is that true?

73s and thanks,
Dave
NK7Z
http://www.nk7z.net

On 04/14/2017 09:53 AM, Jim Brown wrote:
> Yesterday, I got a quote on this part from Dexter, a vendor that has 
> been competitive for past orders. They don't have stock, minimum order 
> is a full box, which is 25 pieces, $15.18 each. 50 pieces is $14.27 
> (-6%). 100 pieces is $13.57. Delivery was quoted as 14 weeks.
>
> 73, Jim K9YC

------------------------------

Message: 3
Date: Fri, 14 Apr 2017 11:33:13 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: rfi at contesting.com
Subject: Re: [RFI] New Larger Fair-Rite #31 Toroid
Message-ID:
	<9658385d-a2f1-2df6-5e49-52bd6de6a0d1 at audiosystemsgroup.com>
Content-Type: text/plain; charset=windows-1252; format=flowed

On Fri,4/14/2017 10:26 AM, Dave Cole wrote:
> Jim,
>
> A question for you...  Looking at the "Impedance vs. Frequency vs. 
> Turn count" graph at:
>
> http://www.fair-rite.com/product/round-cable-emi-suppression-cores-263
> 1814002/
>
>
> It looks like these new cores only have two or three K of impedance 
> with  five turns...  Am I interpreting this correctly?

Yes.

>
> If so, then using two of them with five turns becomes the standard if 
> I want more than five K impedance?  Is that true?

The number of turns (and to to the extent that it affects capacitance, wire size and spacing) sets the resonant frequency. The Fair-Rite data is most likely for small diameter wire. If you want the choke to be effective where 5 turns puts it, yes, two chokes in series would be the way to get there. A choke wound with RG8/11 size coax would have the same inductance but more capacitance between windings if those windings are closely spaced, so the resonance would be a bit lower.

And, of course, more turns will lower the resonance even more, and because R also increases with N-squared, also raise the impedance.

73, Jim K9YC

>
> 73s and thanks,
> Dave
> NK7Z
> http://www.nk7z.net
>
> On 04/14/2017 09:53 AM, Jim Brown wrote:
>> Yesterday, I got a quote on this part from Dexter, a vendor that has 
>> been competitive for past orders. They don't have stock, minimum 
>> order is a full box, which is 25 pieces, $15.18 each. 50 pieces is 
>> $14.27 (-6%). 100 pieces is $13.57. Delivery was quoted as 14 weeks.
>>
>> 73, Jim K9YC
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>

------------------------------

Message: 4
Date: Fri, 14 Apr 2017 14:27:01 -0500
From: Chuck Gooden <Chuck.Gooden at comcast.net>
To: rfi at contesting.com
Subject: Re: [RFI] New Larger Fair-Rite #31 Toroid
Message-ID: <e2486898-80d8-8d11-6623-59cc46ca35e9 at comcast.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

Jim,

Could you clarify if you mean 5 turns through each core as in separate chokes in series.  Or 5 turns through both cores as in 1 choke with two cores? Or is there a difference?  It doesn't seem like there would be a difference.

Chuck K9LC

On 4/14/2017 1:33 PM, Jim Brown wrote:
> The number of turns (and to to the extent that it affects capacitance, 
> wire size and spacing) sets the resonant frequency. The Fair-Rite data 
> is most likely for small diameter wire. If you want the choke to be 
> effective where 5 turns puts it, yes, two chokes in series would be 
> the way to get there.

------------------------------

Message: 5
Date: Fri, 14 Apr 2017 13:39:29 -0700
From: Jim Brown <jim at audiosystemsgroup.com>
To: rfi at contesting.com
Subject: Re: [RFI] New Larger Fair-Rite #31 Toroid
Message-ID:
	<66d585ea-9fab-f175-57dd-33716e46e034 at audiosystemsgroup.com>
Content-Type: text/plain; charset=windows-1252; format=flowed

I mean two chokes, each with five turns, wound on the same coax. There is a HUGE difference. Study k9yc.com/RFI-Ham.pdf, which includes a tutorial on how ferrite chokes work.

The chokes in series keep the same resonant frequency (and the broad resonant peak is the range where they work as chokes). Winding only one choke on two cores lowers the resonant frequency by the square root of 2, because there's twice as much L. and Fr varies as the square root of LC).

73, Jim K9YC

On Fri,4/14/2017 12:27 PM, Chuck Gooden wrote:
> Jim,
>
> Could you clarify if you mean 5 turns through each core as in separate 
> chokes in series.  Or 5 turns through both cores as in 1 choke with 
> two cores? Or is there a difference?  It doesn't seem like there would 
> be a difference.
>
> Chuck K9LC
>
>
> On 4/14/2017 1:33 PM, Jim Brown wrote:
>> The number of turns (and to to the extent that it affects 
>> capacitance, wire size and spacing) sets the resonant frequency. The 
>> Fair-Rite data is most likely for small diameter wire. If you want 
>> the choke to be effective where 5 turns puts it, yes, two chokes in 
>> series would be the way to get there.
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi
>

------------------------------

Message: 6
Date: Fri, 14 Apr 2017 17:01:09 -0700
From: Dave Cole <dave at nk7z.net>
To: rfi at contesting.com
Subject: Re: [RFI] New Larger Fair-Rite #31 Toroid
Message-ID: <9d76bfb4-505c-fc9e-70b5-6ea643934e2a at nk7z.net>
Content-Type: text/plain; charset=windows-1252; format=flowed

Thank you Jim!

73s and thanks,
Dave
NK7Z
http://www.nk7z.net

On 04/14/2017 11:33 AM, Jim Brown wrote:
> On Fri,4/14/2017 10:26 AM, Dave Cole wrote:
>> Jim,
>>
>> A question for you...  Looking at the "Impedance vs. Frequency vs.
>> Turn count" graph at:
>>
>> http://www.fair-rite.com/product/round-cable-emi-suppression-cores-26
>> 31814002/
>>
>>
>> It looks like these new cores only have two or three K of impedance 
>> with  five turns...  Am I interpreting this correctly?
>
> Yes.
>
>>
>> If so, then using two of them with five turns becomes the standard if 
>> I want more than five K impedance?  Is that true?
>
> The number of turns (and to to the extent that it affects capacitance, 
> wire size and spacing) sets the resonant frequency. The Fair-Rite data 
> is most likely for small diameter wire. If you want the choke to be 
> effective where 5 turns puts it, yes, two chokes in series would be 
> the way to get there. A choke wound with RG8/11 size coax would have 
> the same inductance but more capacitance between windings if those 
> windings are closely spaced, so the resonance would be a bit lower.
>
> And, of course, more turns will lower the resonance even more, and 
> because R also increases with N-squared, also raise the impedance.
>
> 73, Jim K9YC
>
>>
>> 73s and thanks,
>> Dave
>> NK7Z
>> http://www.nk7z.net
>>
>> On 04/14/2017 09:53 AM, Jim Brown wrote:
>>> Yesterday, I got a quote on this part from Dexter, a vendor that has 
>>> been competitive for past orders. They don't have stock, minimum 
>>> order is a full box, which is 25 pieces, $15.18 each. 50 pieces is 
>>> $14.27 (-6%). 100 pieces is $13.57. Delivery was quoted as 14 weeks.
>>>
>>> 73, Jim K9YC
>> _______________________________________________
>> RFI mailing list
>> RFI at contesting.com
>> http://lists.contesting.com/mailman/listinfo/rfi
>>
>
> _______________________________________________
> RFI mailing list
> RFI at contesting.com
> http://lists.contesting.com/mailman/listinfo/rfi

------------------------------

Subject: Digest Footer

_______________________________________________
RFI mailing list
RFI at contesting.com
http://lists.contesting.com/mailman/listinfo/rfi

------------------------------

End of RFI Digest, Vol 171, Issue 2
***********************************