"Wes Stewart" wrote in message
...
On Tue, 11 May 2004 01:27:50 GMT, "Jerry Martes"
wrote:

[snip]

Let's establish something first. I used to instruct a fourth
year/graduate level microwave measurements lab in which experiment #1
was on the use of slotted lines.

|
| I wonder why such a smart guy like you would ask about how a person
would
|machine a straight slot where a "sraight slot" (sic) isnt (sic) even
needed.

If you don't think the longitudinal slot needs to be straight down the
length of the line then let's stop here.

If I can convince you that it needs to be then we can proceed.

|Why would
|you propose (the) use of "soft copper"(?)

Perhaps I shouldn't have said "soft" copper; nevertheless, copper
isn't the easiest material to machine, and it was you, you should
recall, that mentioned the use of copper water pipe. If you have a
milling machine with five or six feet of table travel, then good for
you, have at it.

|And, why would you put any supports on the
|center conductor when it isnt (sic) necessary to put them on top, where
the probe
|would.be.(?)

The center conductor needs to be precisely located so as to not have
the probe coupling vary as it is moved. This will necessitate a fair
number of disks/beads or whatever. To be precise, the center
conductor diameter should be reduced (or the outer conductor
increased) wherever there is a dielectric support. If you intend to
slot the supports, then the missing dielectric will modify the
effective dielectric constant. Be sure and calculate that effect.


|Besides, at 137 MHZ, is wouldnt be all that necessary to have
|the probe moveable continuously.

Oh, I didn't know that. Apparently General Radio didn't either; they
had a micrometer attached to theirs to measure position to the
thousandths of an inch.

|It is aparent to me that either you want
|to diminish the value of my learning project or you are just not smart.

Why thank you!

|I havent read this antenna news group for very long.

I have, although with some of the inane stuff posted lately, it isn't
often. BTW, it's an *amateur radio* group. I didn't know we had a
band at 137 MHz.

|Your *help* to me is
|hopefully not typical.

No, I believe in this instance that the advice Richard gave you and
what I am trying to give you is atypically better that what you will
usually get.

|I'm trying to learn. What are you trying to do??

Beats the hell out of me.


Well Wes I see it *IS* time to stop this rant. You *are* much more
educated than I am. And I see you as also being smug and negative , at
least as your help applies to my post. Why would I care if the slot was
straight?? That makes no sense to me. I certainly have no reason to
dissuade anyone from making the slot straight. But, why? If you are so
smart, perhaps you can tell me _why_ something is done rather than just
stating "thats the way HP or General Radio did it". What am I missing
here?? I think that it would be nice to have the slot straight, I had
intended to do that a VERY simple way, on a garage sized Bridgeport. Have
you no concept of how to ,machine metal?? I wonder why you even bothered to
post to my question when you make wrong statements.
Please dont go away till you tell why the slot in a line must be straight
if the line is to be used for impedance measurement.
Yeah, Wes, There is an amateur radio group thats interested in monitoring
weather satellites. Does that bother you?? What advice did Richard give
that might help me build a slotted line??
Please take a few minutes to consider the validity of your advice before
offering it. You seem to get side tracked easily like the softness of
copper and the length of what a mill can slot. Try to focus on the fact
that Jerry is trying to learn how to build a slotted line at home. If you
have *ANY* helpfull information I will certainly appreciate hearing it.

Jerry