"Gary Schafer" wrote in message
...
Easiest way to visualize it is with open wire line which has very low
loss. Feeding a non resonant antenna the SWR can be very high on the
line. You can have 50% reflected power on the line. With 100 watts
forward you would then have 50 watts reflected but just about all of
the 100 watts will reach the antenna and be radiated. The only loss
will be the very small loss in the line. (typically a few tenths of a
db loss)

But if all energy is radiated by the antenna, how on earth can you have any
reflected power???? I thought the essential part here is that reflected
energy is the energy that os NOT radiated.

Meindert

On Fri, 21 Nov 2003 06:57:23 +0100, "Meindert Sprang"
wrote:

"Gary Schafer" wrote in message
.. .
Easiest way to visualize it is with open wire line which has very low
loss. Feeding a non resonant antenna the SWR can be very high on the
line. You can have 50% reflected power on the line. With 100 watts
forward you would then have 50 watts reflected but just about all of
the 100 watts will reach the antenna and be radiated. The only loss
will be the very small loss in the line. (typically a few tenths of a
db loss)

But if all energy is radiated by the antenna, how on earth can you have any
reflected power???? I thought the essential part here is that reflected
energy is the energy that os NOT radiated.

Meindert


Think of it this way: You have the same mismatch to the feed line on
both ends.

If your antenna provides a 70 ohm load for a 50 ohm feed line you will
have reflected power from the antenna. That mismatch of impedance is
reflected back down to the transmitter end of the line. The feed line
at the transmitter NO LONGER LOOKS LIKE A 50 OHM LOAD. If a matching
device is placed between the transmitter and the feed line it must
provide the same match at the transmitter end as the antenna does at
the other end of the line. Called a conjugate match. (you can read
about it in your handbook) It is usually a complex impedance made up
of resistance and capacitance or inductance.

Having the same mismatch on each end of the feed line will provide the
same amount of reflected power at both ends of the line. So any power
that gets reflected from the antenna because of the mismatch there
will get re-reflected back toward the antenna again because of the
similar mismatch to the line at the transmitter end.

Regards
Gary

I suspect that there is a big misunderstanding of TERMS, going on here.
Definitions are being misused on both sides......

Lets get the TERMS Fixed and Understood first.

Transmitter = Rf Source that has an impedance of 50 Ohms

Transmission Line = Coaxial Feedline between Transmitter and Antenna
Tuner.
Antenna Tuner = Device that matches impedance of it's input (50 Ohms)
to that of the antenna that connects to the tuners
output.
Antenna = Effectivly a wire, or pipe, or other conducting structure
used to radiate RF Energy supplied by the Transmitter to
the feedline.

NOW that we have these definitions settled, Please continue the
discussion.

Bruce in alaska
--
add a 2 before @

I think we all kind of sort of knew this Bruce.

Doug

"Bruce in Alaska" wrote in message
...
I suspect that there is a big misunderstanding of TERMS, going on here.
Definitions are being misused on both sides......

Lets get the TERMS Fixed and Understood first.

Transmitter = Rf Source that has an impedance of 50 Ohms

Transmission Line = Coaxial Feedline between Transmitter and Antenna
Tuner.
Antenna Tuner = Device that matches impedance of it's input (50 Ohms)
to that of the antenna that connects to the tuners
output.
Antenna = Effectivly a wire, or pipe, or other conducting structure
used to radiate RF Energy supplied by the Transmitter to
the feedline.

NOW that we have these definitions settled, Please continue the
discussion.

Bruce in alaska
--
add a 2 before @

In article ,
"Doug Dotson" wrote:

I think we all kind of sort of knew this Bruce.

Doug

"Bruce in Alaska" wrote in message
...
I suspect that there is a big misunderstanding of TERMS, going on here.
Definitions are being misused on both sides......

Lets get the TERMS Fixed and Understood first.

Transmitter = Rf Source that has an impedance of 50 Ohms

Transmission Line = Coaxial Feedline between Transmitter and Antenna
Tuner.
Antenna Tuner = Device that matches impedance of it's input (50 Ohms)
to that of the antenna that connects to the tuners
output.
Antenna = Effectivly a wire, or pipe, or other conducting structure
used to radiate RF Energy supplied by the Transmitter to
the feedline.

NOW that we have these definitions settled, Please continue the
discussion.

Bruce in alaska
--
add a 2 before @



Really, then why are folks talking about SWR on the Feedline as being 3:1
or sum such when the feedline in reference system above would have no
SWR as it is at 50 Ohms on both ends???? TERMS are significant, and
Larry, and the rest are mixing them thoughout this whole thread.

Bruce in alaska
--
add a 2 before @

TERMS are significant.

Bruce,

Don't say that too loud. I've already been down that road with Jax.

Ron

One exception, in this case we are talking about an antenna tuner with
its output going to a coax line that then goes to the antenna. The
antenna being something near 50 ohms but far enough from it to produce
a 3:1 SWR on its feed line.

So in this case we have 2 transmission lines. One between the
transmitter and the tuner and one between the tuner and the antenna.

Regards
Gary


On Fri, 21 Nov 2003 21:40:42 GMT, Bruce in Alaska
wrote:

I suspect that there is a big misunderstanding of TERMS, going on here.
Definitions are being misused on both sides......

Lets get the TERMS Fixed and Understood first.

Transmitter = Rf Source that has an impedance of 50 Ohms

Transmission Line = Coaxial Feedline between Transmitter and Antenna
Tuner.
Antenna Tuner = Device that matches impedance of it's input (50 Ohms)
to that of the antenna that connects to the tuners
output.
Antenna = Effectivly a wire, or pipe, or other conducting structure
used to radiate RF Energy supplied by the Transmitter to
the feedline.

NOW that we have these definitions settled, Please continue the
discussion.

Bruce in alaska

In article ,
Gary Schafer wrote:

One exception, in this case we are talking about an antenna tuner with
its output going to a coax line that then goes to the antenna. The
antenna being something near 50 ohms but far enough from it to produce
a 3:1 SWR on its feed line.

So in this case we have 2 transmission lines. One between the
transmitter and the tuner and one between the tuner and the antenna.

Regards
Gary



Actually, in the "Marine Radio" context anything that connects to
the High Impedance side of the tuner is considered not Feedline
but part of the antenna. OK, if just call that part "Transmission Line"
rather than a second feedline? this will allow discussee's to
differentate between the two pieces of the reference system, and
not get them confused while making their points.....

Bruce in alaska
--
add a 2 before @

On Sat, 22 Nov 2003 19:01:50 GMT, Bruce in Alaska
wrote:

In article ,
Gary Schafer wrote:

One exception, in this case we are talking about an antenna tuner with
its output going to a coax line that then goes to the antenna. The
antenna being something near 50 ohms but far enough from it to produce
a 3:1 SWR on its feed line.

So in this case we have 2 transmission lines. One between the
transmitter and the tuner and one between the tuner and the antenna.

Regards
Gary



Actually, in the "Marine Radio" context anything that connects to
the High Impedance side of the tuner is considered not Feedline
but part of the antenna. OK, if just call that part "Transmission Line"
rather than a second feedline? this will allow discussee's to
differentate between the two pieces of the reference system, and
not get them confused while making their points.....

Bruce in alaska


Well, this thing started out as a discussion of SWR on a 50 ohm VHF
feed line. Nothing to do with HF single ended antennas and associated
couplers.

HF got mixed in to the discussion because most are familiar with coax
line antenna tuners. 50 ohm in 50 ohm or near that out. The principles
are the same of course.

With HF things are a little easier to manipulate to do test on than
VHF.

My referring to "feed line" or "transmission line" are all referring
to coax cable. One is synonymous with the other.

I think most are using the same terms.

Sorry for any confusion.

Regards
Gary