1. Does achieving a conjugate match via a transmatch between the
transmitter and line do anything to reduce or eliminate mismatch loss
in the line? In other words, if a line is 8:1 swr into a complex
impedance load are the 8:1 "mismatch" losses still occurring even
after achieving low swr with a transmatch?

2. (Unrelated to first question) After installation of a choke at the
antenna input, swr on my off center fed dipole is surprisingly flat
across the amateur bands, never rising much above 8:1 and this only on
the high end of 80 meters. Reading Maxwell's "Reflections" series, it
seems that this may be due to saturation of the choke at higher
frequencies and I may have introduced non negligible loss into my
antenna system. The choke was made by winding my RG-58 coax through a
3" toroid of unknown permeability (14 turns). Other than the toroid
being solid black, I can't tell you anymore about it. I am using an
MFJ-259B for measurements. It would seem to me the 259B would not be
capable of delivering enough power to saturate the large toroid so
maybe my "too flat" readings are occurring due to something else.

Any advice on the above much appreciated. Please include a comment on
the ability of the 259B to be affected by toroid saturation.

"dykesc" wrote in message
...
1. Does achieving a conjugate match via a transmatch between the
transmitter and line do anything to reduce or eliminate mismatch loss
in the line? In other words, if a line is 8:1 swr into a complex
impedance load are the 8:1 "mismatch" losses still occurring even
after achieving low swr with a transmatch?

yes


2. (Unrelated to first question) After installation of a choke at the
antenna input, swr on my off center fed dipole is surprisingly flat
across the amateur bands, never rising much above 8:1 and this only on
the high end of 80 meters. Reading Maxwell's "Reflections" series, it
seems that this may be due to saturation of the choke at higher
frequencies and I may have introduced non negligible loss into my
antenna system. The choke was made by winding my RG-58 coax through a
3" toroid of unknown permeability (14 turns). Other than the toroid
being solid black, I can't tell you anymore about it. I am using an
MFJ-259B for measurements. It would seem to me the 259B would not be
capable of delivering enough power to saturate the large toroid so
maybe my "too flat" readings are occurring due to something else.

i wouldn't call 8:1 'flat', i aim for 2:1 across the 6 hf contest bands,
excluding the high end of 80m. an important consideration is the length of
that rg-58 and what kind of condition it is in. with only 1db of loss in
the cable you could get 8:1 with almost an open or short circuit at the
antenna end... that would be about 50' at 28MHz.



Any advice on the above much appreciated. Please include a comment on
the ability of the 259B to be affected by toroid saturation.

no, the 259b won't saturate your toroid, but a very lossy toroid could be
contributing to the 'flatness'.

dykesc wrote:
1. Does achieving a conjugate match via a transmatch between the
transmitter and line do anything to reduce or eliminate mismatch loss
in the line? In other words, if a line is 8:1 swr into a complex
impedance load are the 8:1 "mismatch" losses still occurring even
after achieving low swr with a transmatch?

In an ideal system, achieving a conjugate match at the
transmatch ensures a conjugate match between the tuner
and the antenna. In a low-loss system, that conjugate
match is close but not perfect. A conjugate match and
an impedance match are NOT the same thing if the SWR
is not 1:1 on the transmission line.

A conjugate match ensures that maximum power is delivered
to the load which ensures maximum current in the transmission
line which ensures maximum losses in the transmission line
due to SWR.

A conjugate match does not change the impedance mismatch
or SWR between the transmatch and the antenna. What is
usually achieved by a transmatch is a Z0-match at a point.
A Z0-match usually ensures that reflected energy will not
reach the source and is instead, redistributed back toward
the antenna.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

"Dave" wrote in message
...

"dykesc" wrote in message
...
1. Does achieving a conjugate match via a transmatch between the
transmitter and line do anything to reduce or eliminate mismatch loss
in the line? In other words, if a line is 8:1 swr into a complex
impedance load are the 8:1 "mismatch" losses still occurring even
after achieving low swr with a transmatch?

yes

Think of the conjugate match from the transmatch as making the line to look
as if a 1/2 wave line and transforming to it. There will still be resistive
losses in the tuner and line accentuated by higher than normal voltages and
currents.


2. (Unrelated to first question) After installation of a choke at the
antenna input, swr on my off center fed dipole is surprisingly flat
across the amateur bands, never rising much above 8:1 and this only on
the high end of 80 meters. Reading Maxwell's "Reflections" series, it
seems that this may be due to saturation of the choke at higher
frequencies and I may have introduced non negligible loss into my
antenna system. The choke was made by winding my RG-58 coax through a
3" toroid of unknown permeability (14 turns). Other than the toroid
being solid black, I can't tell you anymore about it. I am using an
MFJ-259B for measurements. It would seem to me the 259B would not be
capable of delivering enough power to saturate the large toroid so
maybe my "too flat" readings are occurring due to something else.

i wouldn't call 8:1 'flat', i aim for 2:1 across the 6 hf contest bands,
excluding the high end of 80m. an important consideration is the length
of
that rg-58 and what kind of condition it is in. with only 1db of loss in
the cable you could get 8:1 with almost an open or short circuit at the
antenna end... that would be about 50' at 28MHz.



Any advice on the above much appreciated. Please include a comment on
the ability of the 259B to be affected by toroid saturation.

no, the 259b won't saturate your toroid, but a very lossy toroid could be
contributing to the 'flatness'.

aggreed

dykesc wrote:
1. Does achieving a conjugate match via a transmatch between the
transmitter and line do anything to reduce or eliminate mismatch loss
in the line? In other words, if a line is 8:1 swr into a complex
impedance load are the 8:1 "mismatch" losses still occurring even
after achieving low swr with a transmatch?

2. (Unrelated to first question) After installation of a choke at the
antenna input, swr on my off center fed dipole is surprisingly flat
across the amateur bands, never rising much above 8:1 and this only on
the high end of 80 meters. Reading Maxwell's "Reflections" series, it
seems that this may be due to saturation of the choke at higher
frequencies and I may have introduced non negligible loss into my
antenna system. The choke was made by winding my RG-58 coax through a
3" toroid of unknown permeability (14 turns). Other than the toroid
being solid black, I can't tell you anymore about it. I am using an
MFJ-259B for measurements. It would seem to me the 259B would not be
capable of delivering enough power to saturate the large toroid so
maybe my "too flat" readings are occurring due to something else.


You can use your 259 to measure the permeability of your toroid, and
infer what mix it is.

Measure the inductance of an inductor with a few turns on the toroid.

From that, you can get the inductance factor.. a few minutes searching
the catalog will probably find a match, given the physical size.

Thanks Dave, Cecil and JB for taking the time to reply. Sounds like
even with a conjugate match at the transmitter, I need to calculate
total line losses based on SWR readings without the transmatch in the
line. Also thanks for the advice on the choke and 259B. I could have a
lossy toroid making things look better than they actually are. I
believe I'll try making an air core choke by simply coiling turns in
the coax at the antenna connection and see how that changes things.
Actually even with the toroid choke the antenna is working pretty well
for the wire antenna and low power setup I have here. Fun trying
different things though and I like to fiddle around.

73s
Dykes AD5VS in Mississippi

dykesc wrote:
I need to calculate
total line losses based on SWR readings without the transmatch in the
line.

If your feedline between the transmatch and the antenna is
50 ohm coax, you can leave the transmatch in the system and
use a separate SWR meter on the output of the transmatch to
measure the SWR on the coax between the transmatch and the
antenna.

If you don't have 50 ohm coax between the transmatch and
the antenna, you are SOL in determining the actual SWR on
the ladder-line or whatever with a standard SWR meter. The
50 ohm SWR reading without the transmatch is completely
different from the actual SWR on the transmission line when
the Z0 is not 50 ohms.

Even the SWR reading looking into ladder-line using an
MFJ-259B is nowhere near the actual SWR on the ladder-
line. For instance, a 50 ohm SWR meter can read a 1:1
SWR on 450 ladder-line when the actual SWR on the ladder-
line is 9:1.
--
73, Cecil, IEEE, OOTC, http://www.w5dxp.com

On May 15, 1:10*pm, Cecil Moore wrote:

Even the SWR reading looking into ladder-line using an
MFJ-259B is nowhere near the actual SWR on the ladder-
line. For instance, a 50 ohm SWR meter can read a 1:1
SWR on 450 ladder-line when the actual SWR on the ladder-
line is 9:1.

Thanks Cecil, I see what you mean. The 450 ohm line could be seeing an
impedance of 50 ohms making the swr 9:1. The MFJ-259B, being 50 ohm
based, and seeing the 50 ohms would call the swr 1:1. Kind of obvious
but something I probably would have overlooked. I'll get out the
manual for the 259b and see if MFJ cautions the user on this.

73
Dykes AD5VS

dykesc wrote in news:ad161de6-d48c-4ad5-80a0-
:

... Sounds like
even with a conjugate match at the transmitter, I need to calculate
total line losses based on SWR readings without the transmatch in the
line.

Well, that is an approximation based on a number of assumptions. If you
don't know the assumptions, or cannot be sure that they apply, it is better
to calculate the line loss based on the load impedance (or inference from
the input impedance).

See TLLC at http://www.vk1od.net/calc/tl/tllc.php , or TWLLC at
http://www.vk1od.net/calc/tl/tllc.php .

My article "Additional loss due to VSWR" at http://vk1od.net/blog/?p=316
canvasses the issue.

Owen

On May 15, 11:07*pm, Owen Duffy wrote:
See TLLC athttp://www.vk1od.net/calc/tl/tllc.php, or TWLLC athttp://www.vk1od.net/calc/tl/tllc.php.

My article "Additional loss due to VSWR" athttp://vk1od.net/blog/?p=316
canvasses the issue.

Owen

Thanks Owen. Very useful and an eye opener for me.