On Sun, 05 Dec 2004 02:53:35 GMT, (Robert Lay
W9DMK) wrote:

Each and every one of your concerns is deeply appreciated. I had
seriously about measuring that 4700 ohm resistor by itself for just
the reasons that you mention. The reason that I did not is quite
simple. The Resistance dial on the General Radio Model 1606B RF Bridge
only goes to 1000 ohms. C'est la Vie!

Say la-la!

Hi Bob,

Good, you have a great piece of equipment, but the implicit question
remains, what do you use to measure the voltage? That is going to be
a serious load across even a 4700 +j0 resistor. Even X10 Scope probes
would be a poor method.

I could have chosen a much lower resistance to start with, but then I
would not have had the desired high SWR, which is critical to the
experiment. You might well ask why I made the switch from a 1/4 wave
open ended stub (at 10.6 Mhz) to the 30 MHz test using the same piece
of line. That was to get a high SWR and still have reasonable
confidence in the value without actually measuring it. Perhaps I
should use a capacitor instead. That's still a possibility.

Hardly worth the thought actually. The 1.5pF stray capacitance would
be a coup-de-grace for the resistor, do you think you could find less
capacitance (with or without the resistor) when there is probably
already that much in fringe capacitance?

I am
thinking of doing it over with a measured 1 k resistor, and just
accepting the SWR of only 20:1. I don't think I have any low ohm
resistors that would give me something around 1 to 3 ohms and still be
low inductance - not from my parts box. Actually, I doubt seriously
that the capacitance effects are as bad as you are suggesting,

They are, life is cruel.

but I
won't argue that without some additional measurements.

It's better than sitting on the park bench with a box of chocolates
and spouting the philosophy of optical interference. For that you get
my Kudos.

My reason for not going with a short circuit was even simpler. I
wanted a concrete value for a non-zero load power.

Regarding the artificial adjustment of the attenuation loss from
around 0.9 up to about 1.72 did not bother me at the time that I did
it, but I can see why it bothers an independant observer. I will have
to do something about that, and perhaps doing it over with a 1 K
resistor is the answer to all of that - so, here goes, and I will get
back to you in a few hours.

Well, one way is to take your measurements and stick with the original
attenuation loss and transform from the input to this 4700 Ohm load.
Does the data suggest this load is closer to my hip shot guess? You
have a reactance built into your results that is unaccounted for, but
comes with this parasitic inclusion I offer.

BTW - this is becoming more and more academic, since I think the real
mystery has been resolved, but there's nothing like getting it wrapped
up with a proper ribbon.

It's all academic, Bob. When you have to take more than one exam
(with questions that go beyond parallel parking) to pursue a hobby
it's part of the turf. Owning a GR-1606 caps it.

73's
Richard Clark, KB7QHC