"Robert Lay W9DMK" wrote in message
...
On Fri, 26 Nov 2004 00:24:13 -0000, "Dave" wrote:

the 1/4 wave open end coax looks like a short circuit at the feed point.
so
your reading makes perfect sense.


Dear Dave,

Yes, I believe it does - that is, it makes perfect sense to have a low
resistance and to have a near zero reactive component. What does not
make sense is that the high SWR is supposed to produce outrageous
losses. I don't see values that I can interpret as high losses - quite
the opposite. Maybe I just don't interpret it correctly, but I would
expect it to be several ohms - not 0.57 ohms.

In fact, and this is where it gets ridiculous, the examples in the
ARRL Antenna Book would lead me to believe that the above quarter wave
line would exhibit 20 dB of total losses. In order to get those
numbers the SWR at the load of say 8000 would have to decrease to
1.01:1 at the source end in order to account for 20 dB in losses. (See
the example on page 24-9 of the 17th Edition.)


the cases they talk about in there are figuring the loss in power that you
would be supplying to a load. in your case the load is an infinite
resistance so it receives zero power which is what the arrl book says... in
this case all the power that is sent down the line is reflected back minus a
little bit of heating so the swr at the feedpoint should be near infinite,
but not quite. the actual loss in the wave going down and coming back is
very small hence the very low impedance. this is an effect that is used to
make coaxial stub filters and transformers.