> "Harold Farrenkopf" <[EMAIL PROTECTED]> wrote:
> Easiest way to verify the actual length required is to
> remove the loop from the can (or adjust it for minimal
> coupling) and put it in the star with a cable of
> approximately the correct length and use 2 of the other
> star ports to measure the resonant frequency of the loop
> and cable to see if it is in the mid of your frequency
> spread.
Much of the time, the "mid frequency" is not the most
desired location. I'm not sure if you'd actually call or
spec the cable/loop combo as a "resonant frequency"
element... although most people might call it one.
> All the cables would then be the same length to the
> star if the loops are the same.
Not in all cases... also depend on the number of legs
in use via the star or equiv device. Also the frequency
spread...
> The open stub would be close to the electrical 1/2 wavelength if
> required to make the output return loss symmetrical and better. I
> personally usually do not use a stub and try to make the cables work
> alone but then again, I am using an Agilent 8753ES network analyser
> that makes the job very easy. The stub is used if the frequency span
> is larger or the cables used are not the ideal lengths.
>
> The open circuit stub is trimmed to make the return
> loss symmetrical.
> Harold
>
I've found the shorted stub used most often, Not only as a
trap, but as a much desired (in most cases) dc shunt.
I've seen star combiner setups with various caps and or stubs
networks on the unused ports.
Telewave sells a square box type - star, which I think is
real crap. I like the Sinclair Star mucho betta'.
cheers,
skipp
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