[Elecraft] Re: MFJ259

[Don Wilhelm]

Those who have both an Elecraft N-Gen and a KX1 have everything needed
except the bridge elements to construct and use a relatively compact version
of that Improved Noise Bridge described by John Grebenkemper in that August
1989 QST article.

The N-gen is the noise source and the KX1 can serve as the detector - listen
for the null.  Of course, it is easy to construct the noise generator, so
those with only a portable receiver like the KX1 can have an accurate
impedance meter once it is calibrated.

Detectors other than a receiver can also be used - an AD8307 based power
meter should work just fine and fit into a small case.

The 'disadvantage' of the noise bridge is there are two knobs to deal with,
but when a deep null is achieved one can read both the resistive and the
reactive component of the unknown impedance.

73,
Don W3FPR

> -----Original Message-----

> Dave G3YMC wrote:
>
> > I would also make a plug for a noise bridge. I built the one by KI6WX
> > which appeared in QST in August 1989 (available to download from the
> > ARRL site). If you have a suitable portable rig to couple to it does
> > most of what the fancy analysers can do at a fraction of the cost.
>
> It should not be too difficult to design a fairly simple receiver
> drawing a
> small amount of current to be enclosed with a noise bridge to
> make an 'easy
> to carry' instrument. Top of head thinking.
>
> 73,
> Geoff
> GM4ESD
>
>
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