According to:http://ham.srsab.se/ww/temp/test_MFJ269.pdf
ARRL lab measures the range of the MFJ 269 is 6 to 400
ohms. Not sure what the difference is between this and
the MFJ 259.

Frank

The anti resonant points are well within the MFJ 259 specifications
stated above.

The results you are measuring are certainly within the range of the
MFJ 259. As an example: a 493 ft dipole, 50 ft above an average
ground shows anti-resonance, at 1.9 MHz, and is 15,000 ohms.


Frank