with two different materials, you've basically got two inductors/chokes in
series. You'd have to evaluate them separately at the various frequencies
and sum the contributions at each frequency.
For instance, if you had one that had a real high impedance (say 1kohm) at 2
MHz, and low elsewhere, and the other one had a high impedance (say 2kohms)
at 15 MHz, and low elsewhere, the series combination of the two would just
have the two high impedance bumps at 2 and 15 MHz, where the height of the
bumps is the same as they were standalone (i.e. 1k at 2Mhz and 2k at 15
MHz). you wouldn't get 3kohms.
If they're closely coupled, it will get a bit more complex, but ballparking
it is probably close enough.
----- Original Message -----
From: <N6CW@aol.com>
To: <towertalk@contesting.com>
Sent: Tuesday, March 22, 2005 6:22 AM
Subject: Re: [TowerTalk] Toroid Core Material Selection
> Hi all,
>
> I am always interested in toroid comments. I have been successfully
cleaning
> up a lot of my long-standing RFI problems with them. My question. Ignoring
the
> economics, as I have both types available, what would be the results of
> stacking one each of type 43 and 77 toroids? Would this make a toroid with
the
> combined bandwidth of both and the combined choking impedance of both? And
would
> this result be the same with the same two toroids in series? Type 31
material
> seems like the ultimate weapon but doesn't seem to be readily available
yet.
>
> Terry Baxter/N6CW
>
> In a message dated 3/21/05 10:53:58 PM Pacific Daylight Time,
> W4EF@dellroy.com writes:
>
> << I just made some measurements
> on a 2.4 inch O.D. type 31 Fair-Rite Products core that K9YC
> sent me. 7 turns on this core will give you >1000 ohms choking
> impedance from 1.8 to 30 MHz. My data shows that the
> type 31 material is much better than type 77 material in the
> same form factor (2.4 inch O.D. toroid). The impedance of
> the type 77 material falls off pretty rapidly above 2 MHz,
> whereas the 31 material seems to provide good series
> impedance well past 30 MHz. >>
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
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_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
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