[MFJ-Ameritron] MFJ-259B impedance reading

[Andy]

> I never tried this before but was messing with my antenna tuner and
> decided to compare my antenna impedance reading with a precision 50ohm
> resistor.

What exactly does "precision resistor" mean?

Can you measure its resistance with an accurate DVM?

Is it supposed to be a good RF resistor too?

At what frequency did you measure it on the '259B?

Using what leads, or connectors?  How is it constructed?

> I noticed that the resistor reads 58 ohms (much to my
> surprise) when connected directly to the antenna jack on the  259B.
>
> Is my instrument in need of calibration or is this typical?

That depends.  See previous questions.

> I would
> think pure resistance should read right on.

Well, "pure resistance" that is known to be exactly 50 ohms, should
measure 50 ohms.  Why do you say it is a pure resistance, and do you
know that it really is 50 ohms?

For example, it might be a good 50.0 ohm resistor, but inductance of
the leads could make the Z measure higher.

Even dummy loads, which are supposed to be good over a wide range of
frequencies, can measure off from what you'd think they ought to be.
I've got a good dummy load that measures quite nicely; and some others
that surprisingly do not.

Andy