On Tue, 17 Mar 1998, Gian Luca Salvia wrote:
> Hi all,
> I was wondering if is available a mod for the MN-2000 tuner, to add 160
> meters on.
> Thanks and 73's
>
> Luca IC8WIC
In general, it is usually not good practice to simply modify an 80-10
meter coupler for 160 meter operation (unless one wishes to replace
everything inside and make a true 160 meter tuner).
Although some additional capacitance may allow some sort of match on 160,
it often turns out to be a very lossy match. Low loss matching with
network tuners (and link-coupled tuners as well) normally requires that
the values of available capacitance and inductance be twice what one
needs for 80 meters, while maintaining component Q throughout. While not
impossible (for I would never sell amateur ingenuity short), this is
exceptionally difficult to obtain.
Therefore, I tend to recommend that for 160, one build an ATU from
scratch, with attention to having switchable/variable settings that permit
low loss matches across the entire band.
At my web site are some notes on link coupled tuners, part 5 of which
provides some recommended component sizes for each ham band. While not
exact, these values translate roughly into what is needed for a PI network
tuner, and extrapolations from there to other network designs are possible
in order to get a rough handle on the component size problem/challenge.
More exact network calculations are, of course, possible.
-73-
LB, W4RNL
L. B. Cebik, W4RNL /\ /\ * / / / (Off)(423) 974-7215
1434 High Mesa Drive / \/ \/\ ----/\--- (Hm) (423) 938-6335
Knoxville, Tennessee /\ \ \ \ / / || / (FAX)(423) 974-3509
37938-4443 USA / \ \ \ \ || cebik@utk.edu
URL: http://funnelweb.utcc.utk.edu/~cebik/radio.html
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