[TowerTalk] ferrites for antenna tuners?

Jim Lux jimlux at earthlink.net
Wed Nov 9 23:54:23 EST 2005

At 08:34 PM 11/9/2005, Tod wrote:
>Gee Jim,
>That is a very complex engineering challenge. I think you need to provide a
>couple of boundary conditions with respect the power and reactance that must
>be handled. Probably it would be best to pose the query in the form of
>several sub-queries, each one giving specific limits to what MUST be
>I think it is a great question and hope we get some discussion at length. I
>am pretty certain it is one of those things that can at best be bounded with
>out being exactly specified.
>73, Tod, K0TO


Let's say we want L from around 0.1 to 20-30 uH in a 1,2,4 kind of sequence 
(so we'd like to choose cores with a permeability such that we can get an 
exponential sequence with integer numbers of turns)  For instance, the LDG 
AT 11 uses T106-2 cores and the following scheme
Turns uH
1       .11
2       .22
3       .39
4       .59
7       1.25
11      2.5
17      5.0
25      10

Note well that the uH doesn't track the number of turns squared... (which 
it should...).  I can figure out the turn numbers and inductances needed to 
get all the values I need..

Say we want to handle 10 Amps of RF current

Say we want to limit the loss to 1%

It's the trades over frequency and power that I'm interested in.

Is there any one mix that will work for this (we ARE talking about more 
than a 10:1 frequency range)

> > -----Original Message-----
> > From: towertalk-bounces at contesting.com
> > [mailto:towertalk-bounces at contesting.com] On Behalf Of Jim Lux
> > Sent: Wednesday, November 09, 2005 9:29 PM
> > To: towertalk at contesting.com
> > Subject: [TowerTalk] ferrites for antenna tuners?
> >
> > I'm designing a computer controlled matching network for HF
> > (1.8-30 MHz), and I'm looking for suggestions as to the type
> > and size of the toroids to use in the switchable inductors.
> > Say we're handling currents/voltages at 1kW and higher levels
> > (particularly where there's a lot of reactive power).
> > Stacking toroids is fine to keep the flux reasonable at
> > higher turn numbers.  There's also a compromise between loss
> > and heating of the core.
> >
> >

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