[UK-CONTEST] VHF Combiner

[Nick Gregory]

Thanks Chaps,

Just done the maths and having one port o/c of a two port combiner gives a
VSWR of 2:1

coef = R1 - R2
          -----------
          R1 + R2

          100 - 50
          ------------
          100 + 50

          = coef 0.33 or VSWR 1.98:1

so what I measured was correct.

My club has a MFJ259 so will put my existing combiners and the current
project on the meter.

Thanks for the input. look's like I on the right track.

Regards

Nick G0HIK




On 14/02/2010, Ray Hills <g3hrh at btinternet.com> wrote:
>
> Nick,
>
> The impedance you have is close enough to 50 ohms.  You would not notice
> the
> difference.  But shortening the quarterwave sections will introduce
> reactance which will also affect the input impedance.  Were it me, I would
> settle for the 52 ohms.  Your method of testing is fine in principle.  It
> will be as accurate as the SWR bridge that you use.  Again were it me I
> would be using my MFJ259 which is good enough for all practical purposes.
> In practice the input impedance will be largely dependent on the impedance
> of the antennas rather than the actual combiner.  There are several options
> for the combiners, e.g. two-one and four-one.  The WIMO web page has some
> useful ideas.
>
> Ray G3HRH
>
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