Tod - MN wrote:
>
> Ron:
> As you can see, matching using an L network at the input can produce good
> results with fairly simple to create coils. You can tune the base network to
> the center of the band segment of interest and it should be broad enough to
> reduce the SWR over a reasonable range of frequencies. If you are using
> RG-213 to feed the antenna, the losses at 1.8 MHz for reasonable lengths and
> VSWR's up to say 5:1 will be trivial. That should allow you to use your
> tuner at the shack to match the transmitter as required. Since the SWR of 15
> -j150 is about 33:1 and 15 -j50 about 7:1 the tuner losses should be much
> less when you "prematch" at the input and fine match at the station.
>
> I hope that is useful information.
>
> Tod, KØTO
Let me throw a small monkey wrench into this. If you have an accurate
set of measurements at the base of the antenna and a Smith chart
program, you can achieve a wider bandwidth by NOT adjusting the L
network to an SWR of 1:1 at a specific frequency. The trick is to
set the SWR circle on the Smith chart to the max value desired and
then to move the impedance plot until the the greatest range of values
are within the SWR circle. This will give you a "W" shaped SWR plot
where no place is 1:1 but the maximum range is within the specified
range of SWR.
73, Roger
--
Remember the USS Liberty (AGTR-5)
http://ussliberty.org/
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