On Mon, 10 May 2004 06:22:29 GMT, "Jerry Martes"
wrote:
I was hoping to get a response from someone who either had built a line or
knew of a publication on the pitfalls associated with making a slotted line.

Hi Jerry,

In response to this, and your email, your wishes are most likely to
evince a deafening silence. If you are trying to survey those who
have built one from a population of those who used them, I think
you've already hit a saturation of 2 possible users. Your own
construction effort would qualify you to expand the population by 50%.

As for why a slab style over a cylinder style. That for me is taken
on faith that greater minds, in the person of HP Metrologists, figured
that one out a long time ago. Myself, I can infer their rationale
that perhaps demands more precision and accuracy than you care to
pursue; but as any path demands a handcrafted solution, why put in 80%
of the effort for a 20% design when 90% effort would double or triple
your return?

Harkening back to my days at Metrology school, I can imagine that the
slab method was chosen because of the inevitable inner line sag that
would inject residual SWR into the system. Sagging between two plates
would seem to me to be a non-issue. Sagging within a cylinder may not
bring enough residual SWR to cause you grief either, but you have to
build and test one to discover the error of your presumption if it
disappoints you.

As for using your scope to eke out the voltage measurements. That is
a tantalizing thought, but the big boys accomplish more with less.
Simplicity is the keyword, with thinking outside of the box. You are
focusing on the literal, absolute voltage measurement when SWR is all
a matter of relativity that affords orders of magnitude more
sensitivity and resolution (and hence accuracy).

Research the Agilent archives for the Metrology papers of the 1960s.
The discussion is very accessible (with only the math necessary to
perform a real measurement) and focused to the concept and the theory.
The writing of that era is a hallmark of clarity.

73's
Richard Clark, KB7QHC