Jim,
The subject was the one to which I responded. "Mismatch" seems to me to be
SWR/VSWR. "Losses" appears to me to be (lost power).
Others have posted about power not making it to the antenna are reflected back
and
forth and eventually make it to the antenna and are radiated. This is so absurd
that I had to respond to that one.
I believe my post was apples to apples.
I meant no response to anything you said/posted, I was just responding to the
thread.
Just so we're on the same page, I am not talking about the attenuation in a
cable
based on its length. I am pointing out that mismatch losses are due to the
combination of that, plus VSWR.
Where your discussion about loss/distortion caused by reflected power leaving
the
antenna later...etc...is your business. That has nothing to do with my post
and I
was not referring to that. I have no confusion with time distortion on a
transmission line. That is a separate subject. The problem is that the
messge/thread subject did not say "phase distortion". It said "mismatch loss".
And those responding to it tried to explain it differently than it is explained
in
Physics.
Please don't change the subject of my messages. If you have an opinion, fine.
But respond to the subject at issue.
AND, I stand by my post as accurate and responsive to the thread.
Bill, N3RR
Jim Reid wrote:
> At 00:21 6/28/98 +0100, Bill Hider, N3RR wrote:
> >Gentlemen,
> >
> >Yes, it's true. Sometimes it makes a difference. Sometimes it's significant.
> >And there is a reference to go to to determine what it is!!
>
> Unfortunately, the reference you site below, is too a completely
> different "it" (loss mechanism)! See on below.
> >
> >Per the ARRL Handbook, 1994, Chapter 16 (Transmission Lines), page 16-14
> through
> >16-15, the following is a summary of Fig 26, a graph showing on the x axis: %
> >relative power delivered to the antenna; and y axis: VSWR at input end
> (i.e., at
> >the transmitter) of the transmission line, and a family of curves
> depicting the
> >transmission line loss at the frequency of interest if the load is matched to
> >the line (i.e., the manufacturer's spec dB/ft times # of feet used):
> >
> >For 1:1 VSWR (at xmtr) and lossless transmission line, % power delivered
> to the
> >antenna = 100%
> >For 1:1 VSWR (at xmtr) and 1 dB loss in transmission line, per mfg., % power
> >delivered to antenna = 80%
> >For 1:1 VSWR (at xmtr) and 2 dB loss in transmission line, per mfg., % power
> >delivered to antenna = 63% (eyeball interpolation)
> >For 2:1 VSWR (at xmtr) and 1 dB loss in transmission line, per mfg., % power
> >delivered to antenna = 73% (eyeball again)
> >
> >The "lost" power is dissipated in I Squared R losses (H E A T) in the
> copper (or
> >other metal) in the transmission line.
>
> BUT, Bill, you are talking apples, my post is/was about oranges!
>
> I presented NO argument against the "copper losses", I-squared-R
> losses, which is what the ARRL tables/graph you refer to is all about.
>
> My argument is to refute Robert's assertion that there is also real,
> meaningful loss/distortion/per him, noise, caused by the reflected
> power exiting the cable later than the non-reflected power. A
> completely different phenomena, and one which must be stopped
> from spreading, as it just t'aint true.
>
> In fact the "problem" which Robert addresses is even less than
> my suggestion, as I didn't make a point about the continual
> diminution of the energy being re-reflected to form his
> asserted after "dit" echo. Obviously after 10 or so round trips
> up and down the line, the "echo" will be many, many dB
> down from the initial impulse of which Robert was sounding
> the alarm. My post simply refutes the importance of that
> phenomena.
>
> And good that you post info about losses to your web site,
> but certainly do not confuse reelection phase (time) distortion
> with copper losses and their increase with vswr on the
> transmission line. Totally separate issues.
>
> 73, Jim, KH7M
>
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