Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

As we all agree, under equal output impedance and load impedance
conditions, onty half the RF generated reaches the load. This is sim;ly
not acceptable or likely for any real-world transmitter. Do 50kW radio
station output valves dissipate 50kW? I hope not!

You are attempting to mix circuit theory and transmission line theory.

The "valves" in a transmitter are not connected to the transmission
line. The "valves" in a transmitter are a voltage source connected
to an impedance matching network which then connects to a transmission
line.

A 50kW radio station does not generate 50kW of power, it generates
a voltage that results in 50kW being dissipted into a 50 Ohm load.

There is a difference.


--
Jim Pennino

wrote:

Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

As we all agree, under equal output impedance and load impedance
conditions, onty half the RF generated reaches the load. This is sim;ly
not acceptable or likely for any real-world transmitter. Do 50kW radio
station output valves dissipate 50kW? I hope not!

You are attempting to mix circuit theory and transmission line theory.


You rather have to if you are going to connect a practical circuit to a
practical transmission line!



The "valves" in a transmitter are not connected to the transmission
line. The "valves" in a transmitter are a voltage source connected
to an impedance matching network which then connects to a transmission
line.

Fair enough. Do you want to dissipate 50kW in the matching circuit




A 50kW radio station does not generate 50kW of power, it generates
a voltage that results in 50kW being dissipted into a 50 Ohm load.

There is a difference.

Not much, seeing it also has to supply the in-phase current to maintain
that voltage across the resistive 50 ohm load.







--
Roger Hayter

Roger Hayter wrote:
wrote:

Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

As we all agree, under equal output impedance and load impedance
conditions, onty half the RF generated reaches the load. This is sim;ly
not acceptable or likely for any real-world transmitter. Do 50kW radio
station output valves dissipate 50kW? I hope not!

You are attempting to mix circuit theory and transmission line theory.


You rather have to if you are going to connect a practical circuit to a
practical transmission line!

Nope.

In the real world you pick a system impedance to match the transmission
line you want to use.

You design the transmitter with circuit theory to match the line.

You design the antenna with electromagetic theory to also match the line.

The "valves" in a transmitter are not connected to the transmission
line. The "valves" in a transmitter are a voltage source connected
to an impedance matching network which then connects to a transmission
line.

Fair enough. Do you want to dissipate 50kW in the matching circuit

What anyone wants is irrelevant to physics.

A 50kW radio station does not generate 50kW of power, it generates
a voltage that results in 50kW being dissipted into a 50 Ohm load.

There is a difference.

Not much, seeing it also has to supply the in-phase current to maintain
that voltage across the resistive 50 ohm load.

The phase of a transmitter is what it is and this is a red herring.


--
Jim Pennino

On 7/5/2015 5:24 PM, wrote:
Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

Where is the source impedance found on a Smith chart? Also, if you have
EZNEC, you will not find a place to specify source impedance but it will
show the SWR.

John S wrote:
On 7/5/2015 5:24 PM, wrote:
Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

Where is the source impedance found on a Smith chart? Also, if you have
EZNEC, you will not find a place to specify source impedance but it will
show the SWR.

A Smith chart is normalized to 1.

EZNEC allows you to set the impedance to anything you want and assumes
the transmission line matches the transmitter.

--
Jim Pennino

On 7/5/2015 7:21 PM, wrote:
John S wrote:
On 7/5/2015 5:24 PM, wrote:
Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

Where is the source impedance found on a Smith chart? Also, if you have
EZNEC, you will not find a place to specify source impedance but it will
show the SWR.

A Smith chart is normalized to 1.


So, it can't be used in a 50 ohm environment? What does that have to do
with anything? The chart has a SWR graph and nowhere does it need source
impedance. If you disagree, please link to one.


EZNEC allows you to set the impedance to anything you want and assumes
the transmission line matches the transmitter.

Please show the EZNEC statement that "assumes the transmission line
matches the transmitter". Look in the help section if you have EZNEC and
can cut and paste or just refer me to the chapter and verse. Also, if
you have EZNEC, you can insert a transmission line with arbitrary
characteristic impedance, put a load on the far end matching the line,
and look at the SWR. It will still be 1:1 because the LOAD matches the
LINE. Not because EZNEC assumes a source impedance. Try it with and
report back here.

There is no way that a source initiates reflections. That is a property
of the line and load only. It may re-reflect a wave reflected from the
load, but that is all.

You can also verify this in LTSPICE if you wish.

John S wrote:
On 7/5/2015 7:21 PM, wrote:
John S wrote:
On 7/5/2015 5:24 PM, wrote:
Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

Where is the source impedance found on a Smith chart? Also, if you have
EZNEC, you will not find a place to specify source impedance but it will
show the SWR.

A Smith chart is normalized to 1.


So, it can't be used in a 50 ohm environment? What does that have to do
with anything? The chart has a SWR graph and nowhere does it need source
impedance. If you disagree, please link to one.


EZNEC allows you to set the impedance to anything you want and assumes
the transmission line matches the transmitter.

Please show the EZNEC statement that "assumes the transmission line
matches the transmitter". Look in the help section if you have EZNEC and
can cut and paste or just refer me to the chapter and verse. Also, if
you have EZNEC, you can insert a transmission line with arbitrary
characteristic impedance, put a load on the far end matching the line,
and look at the SWR. It will still be 1:1 because the LOAD matches the
LINE. Not because EZNEC assumes a source impedance. Try it with and
report back here.

There is no way that a source initiates reflections. That is a property
of the line and load only. It may re-reflect a wave reflected from the
load, but that is all.

You can also verify this in LTSPICE if you wish.

What happens if you take any off the shelf commercial amateur radio
transmitter that does not have a built in tuner and:

Attach a 10 Ohm load.

Attach a 200 Ohm load.

Attach a 1,000 Ohm load.

Attach a 1 Ohm load.

Attach a 50 Ohm load.


--
Jim Pennino

On 7/6/2015 12:19 AM, wrote:
John S wrote:
On 7/5/2015 7:21 PM, wrote:
John S wrote:
On 7/5/2015 5:24 PM, wrote:
Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

Where is the source impedance found on a Smith chart? Also, if you have
EZNEC, you will not find a place to specify source impedance but it will
show the SWR.

A Smith chart is normalized to 1.


So, it can't be used in a 50 ohm environment? What does that have to do
with anything? The chart has a SWR graph and nowhere does it need source
impedance. If you disagree, please link to one.


EZNEC allows you to set the impedance to anything you want and assumes
the transmission line matches the transmitter.

Please show the EZNEC statement that "assumes the transmission line
matches the transmitter". Look in the help section if you have EZNEC and
can cut and paste or just refer me to the chapter and verse. Also, if
you have EZNEC, you can insert a transmission line with arbitrary
characteristic impedance, put a load on the far end matching the line,
and look at the SWR. It will still be 1:1 because the LOAD matches the
LINE. Not because EZNEC assumes a source impedance. Try it with and
report back here.

There is no way that a source initiates reflections. That is a property
of the line and load only. It may re-reflect a wave reflected from the
load, but that is all.

You can also verify this in LTSPICE if you wish.

What happens if you take any off the shelf commercial amateur radio
transmitter that does not have a built in tuner and:

Attach a 10 Ohm load.

Attach a 200 Ohm load.

Attach a 1,000 Ohm load.

Attach a 1 Ohm load.

Attach a 50 Ohm load.



Please address my questions first before setting up another strawman.

John S wrote:
On 7/6/2015 12:19 AM, wrote:
John S wrote:
On 7/5/2015 7:21 PM, wrote:
John S wrote:
On 7/5/2015 5:24 PM, wrote:
Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

Where is the source impedance found on a Smith chart? Also, if you have
EZNEC, you will not find a place to specify source impedance but it will
show the SWR.

A Smith chart is normalized to 1.


So, it can't be used in a 50 ohm environment? What does that have to do
with anything? The chart has a SWR graph and nowhere does it need source
impedance. If you disagree, please link to one.


EZNEC allows you to set the impedance to anything you want and assumes
the transmission line matches the transmitter.

Please show the EZNEC statement that "assumes the transmission line
matches the transmitter". Look in the help section if you have EZNEC and
can cut and paste or just refer me to the chapter and verse. Also, if
you have EZNEC, you can insert a transmission line with arbitrary
characteristic impedance, put a load on the far end matching the line,
and look at the SWR. It will still be 1:1 because the LOAD matches the
LINE. Not because EZNEC assumes a source impedance. Try it with and
report back here.

There is no way that a source initiates reflections. That is a property
of the line and load only. It may re-reflect a wave reflected from the
load, but that is all.

You can also verify this in LTSPICE if you wish.

What happens if you take any off the shelf commercial amateur radio
transmitter that does not have a built in tuner and:

Attach a 10 Ohm load.

Attach a 200 Ohm load.

Attach a 1,000 Ohm load.

Attach a 1 Ohm load.

Attach a 50 Ohm load.



Please address my questions first before setting up another strawman.

Start with Electromagnetics by Kraus and Carver, Chapter 13.


--
Jim Pennino

On 06/07/15 01:21, wrote:
John S wrote:
On 7/5/2015 5:24 PM, wrote:
Roger Hayter wrote:
wrote:


The output impedance of an amateur transmitter IS approximately 50 Ohms
as is trivially shown by reading the specifications for the transmitter
which was designed and manufactured to match a 50 Ohm load.

Do you think all those manuals are lies?

You are starting with a false premise which makes everything after that
false.


A quick google demonstrates dozens of specification sheets that say the
transmitter is designed for a 50 ohm load, and none that mention its
output impedance.

If the source impedance were other than 50 Ohms, the SWR with 50 Ohm
coax and a 50 Ohm antenna would be high. It is not.

Where is the source impedance found on a Smith chart? Also, if you have
EZNEC, you will not find a place to specify source impedance but it will
show the SWR.

A Smith chart is normalized to 1.

That is true but is doesn't address the point. There should still be
somewhere to represent the source impedance, albeit normalised.

EZNEC allows you to set the impedance to anything you want and assumes
the transmission line matches the transmitter.

Likewise, that is a sweeping statement which evades the point.