At 08:10 AM 7/14/2005, Dino Darling wrote:
>Hello John, how do you test your lines and what equipment do you use?
>
>I've experimented with the MFJ 259B for stubs and phasing lines, but if it
>is critical, I'll order lines from M2. I'd sure like a good method that I
>could employ myself. Also, do you short the end of the coax or leave it
>open. The MFJ book lists both methods.
In the network analyzer calibration world, it's considered that it's much
easier to make a good short than a good open. The problem is the fields at
the end of the open are less well controlled. For amateur HF use, it's
probably a wash. The error in the open is probably in the fractions of an
inch equivalent. 1 inch is about a half degree on 20m.
You can also use any precision mismatch. Say you take a couple 50 ohm
loads and connect them with a T to make a 25 ohm load, or, a 3dB pad
terminated into a short.
> >...but I even measure the actual phase shift for each delay line of solid
> >dielectric coax, if the application is critical.
> >
> >And with foam coax it is MANDATORY to TUNE (trim) each delay line to the
> >correct electrical length.
> >
> >--John W0UN
>
>Dino...k6rix@earthlink.net
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