Reg

I would sure like to get some information from you. I think you are the
kind of guy who would know about how this line might be made to work. I
have some 'notions' that may well be wrong, and I'm too easily confused to
work this out alone. It seems to me that a "home made" slotted line wouldnt
have to be 50 ohms, yet it could accurately measure load impedances.
For my purpose, I'd want to try to get the line impedance as close to 50
as practical. But, if the slotted line's impedance was 48 ohms or 52 ohms,
the line would give quite good information on load impedance. That would
require alot of testing to actually determine the Zo of the line. But, I
would like only to get real close. I dont need a lab standard.
Since I've gotten so involved with this news group discussion, I'll start
building a slotted line useing that 5 foot long piece of copper tube at Home
Depot. Still, it would be more satisfying to know more about what I'm
attempting. It occurred to me that, if building a slotted line for
impedance measurement at 137 MHz was easy, someone would have done it
already. So, I'm not real confidant that I'll be successful.
I'd thought I might be able to use my Oscilloscope with a sensitive probe
for the "voltage measurement". But, since I'm hearing nothing from this
group about how slotted lines are home made for VHF impedance measurement,
I'm not confidant I'll be successful.

Of course it is not you who is out of date. It is me. I've been away
from electronics and antennas for the last 35 years.

Jerry





"Reg Edwards" wrote in message
...
A slotted line is a fundamental Standard of Impedance. It relates
impedance
measurements to the absolute standard of length, the International Metre!

Its weakest feature is the probe mechanism itself. Its electrical
presence
is unpredictable. Incalculable. Uncertainty can only be minimised.

Or am I 60 years out of date?

Does anyone know what is the uncertainty in measuring an impedance of,
say,
around 100 ohms at 10 MHz, as may be claimed by a National Measurement
Standards Laboratory.

What may be claimed by an instrument manufacturer in the sales blurb is
another matter.
----
Reg, G4FGQ