It's possible but it would be one heck of a big slug. The material type
and the cross sectional area of the core, which is governed by the power,
is what you have to follow. One can figure this area by using the satndard
formulas for calculating the area with maximum flux density, frequency,
and power throughput. The max. flux density is really low in ferrite thus
a big (huge) core is required. There are also powdered iron cores that can
be used here with similar formulas. Most ferrite and powdered iron
manufacturers have these formulas in their catalogs or on their websites.
There are some silicon steel tape wound cores claimed to work into the HF
band but I'm not experienced with any. I read about this for one type of
Hipersil or Silectron material that used tape as thing a 1 mil. One ruff
idea on the size, in small mobile amps, the output transformer has a total
core length of about 3 inches at least made of 1/2" O.D., by 1/4" I.D.
toroids, 1-1/2 length to a side for roughly 100 watts output. Take this
size and multiply it by 10 or 15 to handle 1000 to 1500 watts.
Will
On Wed, 16 Feb 2005 15:14:29 -0600, Joe Brown <joe.brown@gordmans.com>
wrote:
> Is it possible to use slug tuned coils with any reasonable power? I am
> thinking of moving a ferrite slug in and out of a coil to change the
> inductance, but don't know if it would be too lossy at real power? Is
> there a type of ferrite that could be used for this at HF? Or is this
> just a goofy idea. I want to get rid of the roller inductor in my
> homebrew antenna tuner.
>
> I read an article in an old Ham Radio magazine about a tank circuit for
> a commercial 5KW amp, and they lowered the inductance by moving a
> shorted turn ( a piece of copper pipe) in and out of the tank coil.
> Wondering if can do the same thing with ferrite.
>
> 73, Joe W0DB
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