Lumpy wrote:
Roy Lewallen wrote:
What do you read when you connect a
47 - 75 ohm resistor across the
terminals of your measuring device?

Plain resistors read appropriately.
27ohms, 56 ohms etc.

I don't have a good dummy load. I have a 50 ohm
50w resistor but it's wire wound. It varies all
over the range when I sweep the MFJ.

Known good piece of coax, end shorted or open,
reads 50 ohms when the MFJ is tuned to the quarter
wave of the coax.
. . .

Something's seriously wrong there. A shorted quarter wavelength of coax
should read very high impedance when the far end is shorted and very low
when the far end is open. The only time it should read 50 ohms with the
far end shorted or open is if it has many dB of loss. And no even half
decent coax should have anywhere near that much loss in a quarter
wavelength.

So it appears that either your coax is extremely lossy for some reason
(and I can't think of any mechanism which would cause that much loss
unless the coax is specifically designed to be very lossy for some
special reason) or the meter is oscillating or otherwise misbehaving
when connected to coax.

Roy Lewallen, W7EL