"Cecil Moore" wrote in message
...
Jerry Martes wrote:
As you know, I built that slotted line that works fairly well for load
impedance measurements at 2 meters, and can be used at 100 MHz for FM
antenna work.

A pick-up loop will do the same thing for ladder-line.
--
73, Cecil http://www.qsl.net/w5dxp



Cecil

I've always ignored the use of twin lead for impedance measurement. But,
it makes sense. I may try building something like that, just for fun.

I certainly havent thought this "twin lead" line thru but it seems that
one could be easily built from a length of PVC pipe with wires attached to
its sides.
This seems too easy and relatively accurate for "home in the garage" use.
I'd bet I can find some info on the Internet for FM and TV frequency use.
Thanks for jogging my mind.

Jerry

I still remember a demonstration of transmission line phenomena given by
Dick Silberstein, W0YBF, at the Denver Radio Club more than 30 years
ago. He had made a "slotted line" (more accurately a trough line) from a
wire tightly suspended in the "V" of a piece of angle aluminum or steel.
It worked very well. It was pretty large -- I believe the frequency he
used was around 50 MHz. You could use a smaller piece of angle material
or suspend it deeper in the valley for a higher frequency.

Roy Lewallen, W7EL

Jerry Martes wrote:

Cecil

I've always ignored the use of twin lead for impedance measurement. But,
it makes sense. I may try building something like that, just for fun.

I certainly havent thought this "twin lead" line thru but it seems that
one could be easily built from a length of PVC pipe with wires attached to
its sides.
This seems too easy and relatively accurate for "home in the garage" use.
I'd bet I can find some info on the Internet for FM and TV frequency use.
Thanks for jogging my mind.

Jerry

Roy

That trough configuration is probably more practical than the copper tube
coax thing I made. I dont have any current interest in 50 MHz impedance
measurement. But, I'll sure consider that "angle trough" method for any low
cost tools for impedance measurements. I realize now that a slotted line
even for 137 MHz is too large to have around in my garage. It requires too
much room to set up the equipment. It is kinda interesting to consider
something made from PVC so it is "disposable". I dont know how I'd handle
the transitions to and from the coax. But, it seems like a guy could use a
couple 4:1 baluns to get from 50 ohm coax to 200 ohm twin lead. I'm
pretty sure I could find a couple long lengths of copper wire or tube that I
could attach along the sides of some 1 inch PVC to make a 200 ohm line.
That would be about 20 feet long for 6 meters. Wow, thats big.

Maybe I should just get back to learning EZNEC. You guys actually get
good impedance predictions for almost any antenna.

Jerry




"Roy Lewallen" wrote in message
...
I still remember a demonstration of transmission line phenomena given by
Dick Silberstein, W0YBF, at the Denver Radio Club more than 30 years ago.
He had made a "slotted line" (more accurately a trough line) from a wire
tightly suspended in the "V" of a piece of angle aluminum or steel. It
worked very well. It was pretty large -- I believe the frequency he used
was around 50 MHz. You could use a smaller piece of angle material or
suspend it deeper in the valley for a higher frequency.

Roy Lewallen, W7EL

Jerry Martes wrote:

Cecil

I've always ignored the use of twin lead for impedance measurement.
But, it makes sense. I may try building something like that, just for
fun.

I certainly havent thought this "twin lead" line thru but it seems that
one could be easily built from a length of PVC pipe with wires attached
to its sides.
This seems too easy and relatively accurate for "home in the garage"
use. I'd bet I can find some info on the Internet for FM and TV frequency
use. Thanks for jogging my mind.

Jerry