Elecraft

Feature wanted for W2 wattmeter

Classic

List

Threaded

17 messages Options

Vic Rosenthal

Feature wanted for W2 wattmeter

I would like the W2 wattmeter to be able to display "delivered" power,
that is, forward power minus reflected power.

This would give a more accurate indication of power going to an antenna
when the SWR is not 1:1.

For example, if the SWR on the line is about 2.5 and forward power
indicates 1.2 kW, there is about 200 watts reflected power. In that case
only about 1 kW (less line losses, of course) is being delivered to the
load. It is misleading to look at just forward power.

I know that many people think it's simpler to make the antenna impedance
50 ohms, but that's not always possible.

With the W2's Windows application you can see both forward and reflected
power and subtract. But I would like the LEDs on the W2 to be able to
show the delivered power.

Some high-end wattmeters like the Alpha 4510 can do this. It's a SMOP,
so why not?

--
73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Jim Brown-10

Re: Feature wanted for W2 wattmeter

On Mon,1/12/2015 7:56 AM, Vic Rosenthal 4X6GP/K2VCO wrote:
> I would like the W2 wattmeter to be able to display "delivered" power,
> that is, forward power minus reflected power.

You want N8LP's excellent LP-100A. I had lusted after one for quite a
while, and bought W6OSP's unit after he died for about half price. The
LP-100A supports two couplers, which can be deployed on the outputs of
both transmitters in an SO2R setup, or on input and output of a power
amp. The LP-100A measures the complex Z at the coupler, so it can
measure the input Z of the amplifier under dynamic conditions.

Now that I can measure power more accurately, I am able to run a dB or
more closer to legal limit when I want to for contesting.

73, Jim K9YC
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Vic Rosenthal

Re: Feature wanted for W2 wattmeter

I definitely want an LP100A, but I HAVE a W2, and while it is not as
accurate, I still would like to see the delivered power!

On 12 Jan 2015 21:12, Jim Brown wrote:

> On Mon,1/12/2015 7:56 AM, Vic Rosenthal 4X6GP/K2VCO wrote:
>> I would like the W2 wattmeter to be able to display "delivered" power,
>> that is, forward power minus reflected power.
>
> You want N8LP's excellent LP-100A. I had lusted after one for quite a
> while, and bought W6OSP's unit after he died for about half price. The
> LP-100A supports two couplers, which can be deployed on the outputs of
> both transmitters in an SO2R setup, or on input and output of a power
> amp. The LP-100A measures the complex Z at the coupler, so it can
> measure the input Z of the amplifier under dynamic conditions.
>
> Now that I can measure power more accurately, I am able to run a dB or
> more closer to legal limit when I want to for contesting.
>
> 73, Jim K9YC

--
73,
Vic, 4X6GP/K2VCO
Rehovot, Israel
http://www.qsl.net/k2vco/
______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Phil Hystad-3

Re: Feature wanted for W2 wattmeter

Vic,

What do you mean by "delivered power"? I presume you mean delivered to the antenna (aka antenna system) but are you thinking power input to the W2 minus all the losses. By all losses I mean all losses on transmission line due to just plane old cable loss and higher losses due to higher SWR plus any loss in tuner or other devices between W2 and the aether.

Because, due to conservation of energy, that RF energy either goes out into Electromagnetic waves (radiated) or it ends up as heat-loss somewhere in the system.

And, given all that, I don't think any RF/SWR power meter on the market can measure "delivered power".

Or, are you talking about something else.

73, phil, K7PEH

> On Jan 12, 2015, at 11:31 AM, Vic Rosenthal 4X6GP/K2VCO <[hidden email]> wrote:
>
> I definitely want an LP100A, but I HAVE a W2, and while it is not as accurate, I still would like to see the delivered power!
>
> On 12 Jan 2015 21:12, Jim Brown wrote:
>> On Mon,1/12/2015 7:56 AM, Vic Rosenthal 4X6GP/K2VCO wrote:
>>> I would like the W2 wattmeter to be able to display "delivered" power,
>>> that is, forward power minus reflected power.
>>
>> You want N8LP's excellent LP-100A. I had lusted after one for quite a
>> while, and bought W6OSP's unit after he died for about half price. The
>> LP-100A supports two couplers, which can be deployed on the outputs of
>> both transmitters in an SO2R setup, or on input and output of a power
>> amp. The LP-100A measures the complex Z at the coupler, so it can
>> measure the input Z of the amplifier under dynamic conditions.
>>
>> Now that I can measure power more accurately, I am able to run a dB or
>> more closer to legal limit when I want to for contesting.
>>
>> 73, Jim K9YC
>
> --
> 73,
> Vic, 4X6GP/K2VCO
> Rehovot, Israel
> http://www.qsl.net/k2vco/
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Phil Salas

Re: Feature wanted for W2 wattmeter

In reply to this post by Vic Rosenthal

"I would like the W2 wattmeter to be able to display "delivered" power,
that is, forward power minus reflected power. This would give a more
accurate indication of power going to an antenna when the SWR is not
1:1. For example, if the SWR on the line is about 2.5 and forward power
indicates 1.2 kW, there is about 200 watts reflected power. In that case
only about 1 kW (less line losses, of course) is being delivered to the
load. It is misleading to look at just forward power."

Actually, "delivered power" is pretty much what you are measuring.
Remember that reflected power is re-reflected by the source and adds
back into the forward power. So in your example, you are transmitting
1200 watts, having 200 watts reflected, then the 200 watts is
re-reflected by the source giving you the 1200 watts. Of course, there
will be transmission line SWR-related losses.

Phil - AD5X

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

k6dgw

Re: Feature wanted for W2 wattmeter

Well ... sort of. Some of the reflected power heats up the ATU and/or
PA depending on the match it sees [actually, some of the forward power
does too, tuners have forward losses]. "Delivered Power" is somewhat
difficult to calculate. Working into a matched, non-reactive load
[common for AM broadcast, at least a number of years ago], it's "I
squared R" where R is the radiation resistance of the antenna ... and
some minor conductor losses in the antenna. Things get pretty sticky if
it's not a matched load.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
- www.cqp.org

On 1/12/2015 4:46 PM, Phil & Debbie Salas wrote:

> Actually, "delivered power" is pretty much what you are measuring.
> Remember that reflected power is re-reflected by the source and adds
> back into the forward power. So in your example, you are transmitting
> 1200 watts, having 200 watts reflected, then the 200 watts is
> re-reflected by the source giving you the 1200 watts. Of course, there
> will be transmission line SWR-related losses.

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Vic Rosenthal

Re: Feature wanted for W2 wattmeter

In reply to this post by Phil Hystad-3

I'm talking about forward minus reflected power. If you neglect losses, that is how much power gets to the antenna to be radiated. A wattmeter that measures forward power will be misleading if the SWR is high. My antenna has an SWR of about 2.5:1 on 40 m. When the transmitter delivers 100 watts to the line, there is about 120 watts forward and 20 watts reflected. I want a mode in which the wattmeter reads 100 watts in this situation.

Maybe 'delivered' is a bad choice of word. I mean something like 'power delivered by the transmitter'. Obviously it would take magic to know how much power gets to the antenna after losses!

Vic K2VCO /4X6GP

> On Jan 13, 2015, at 12:08 AM, Phil Hystad <[hidden email]> wrote:
>
> Vic,
>
> What do you mean by "delivered power"? I presume you mean delivered to the antenna (aka antenna system) but are you thinking power input to the W2 minus all the losses. By all losses I mean all losses on transmission line due to just plane old cable loss and higher losses due to higher SWR plus any loss in tuner or other devices between W2 and the aether.
>
> Because, due to conservation of energy, that RF energy either goes out into Electromagnetic waves (radiated) or it ends up as heat-loss somewhere in the system.
>
> And, given all that, I don't think any RF/SWR power meter on the market can measure "delivered power".
>
> Or, are you talking about something else.
>
> 73, phil, K7PEH
>
>
>> On Jan 12, 2015, at 11:31 AM, Vic Rosenthal 4X6GP/K2VCO <[hidden email]> wrote:
>>
>> I definitely want an LP100A, but I HAVE a W2, and while it is not as accurate, I still would like to see the delivered power!
>>
>>> On 12 Jan 2015 21:12, Jim Brown wrote:
>>>> On Mon,1/12/2015 7:56 AM, Vic Rosenthal 4X6GP/K2VCO wrote:
>>>> I would like the W2 wattmeter to be able to display "delivered" power,
>>>> that is, forward power minus reflected power.
>>>
>>> You want N8LP's excellent LP-100A. I had lusted after one for quite a
>>> while, and bought W6OSP's unit after he died for about half price. The
>>> LP-100A supports two couplers, which can be deployed on the outputs of
>>> both transmitters in an SO2R setup, or on input and output of a power
>>> amp. The LP-100A measures the complex Z at the coupler, so it can
>>> measure the input Z of the amplifier under dynamic conditions.
>>>
>>> Now that I can measure power more accurately, I am able to run a dB or
>>> more closer to legal limit when I want to for contesting.
>>>
>>> 73, Jim K9YC
>>
>> --
>> 73,
>> Vic, 4X6GP/K2VCO
>> Rehovot, Israel
>> http://www.qsl.net/k2vco/
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>

Vic Rosenthal

Re: Feature wanted for W2 wattmeter

In reply to this post by Phil Salas

You are implying that I can arbitrarily increase my power output by detuning my antenna!
You are right that reflected power is re-reflected by the source, but there is a sense in which the 'real' power output in my example is 1 kW.

Vic K2VCO /4X6GP

> On Jan 13, 2015, at 2:46 AM, Phil & Debbie Salas <[hidden email]> wrote:
>
> "I would like the W2 wattmeter to be able to display "delivered" power, that is, forward power minus reflected power. This would give a more accurate indication of power going to an antenna when the SWR is not 1:1. For example, if the SWR on the line is about 2.5 and forward power indicates 1.2 kW, there is about 200 watts reflected power. In that case only about 1 kW (less line losses, of course) is being delivered to the load. It is misleading to look at just forward power."
>
> Actually, "delivered power" is pretty much what you are measuring. Remember that reflected power is re-reflected by the source and adds back into the forward power. So in your example, you are transmitting 1200 watts, having 200 watts reflected, then the 200 watts is re-reflected by the source giving you the 1200 watts. Of course, there will be transmission line SWR-related losses.
>
> Phil - AD5X
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Vic Rosenthal

Re: Feature wanted for W2 wattmeter

In reply to this post by k6dgw

What I want is just forward - reflected. Neglecting losses, this is what the tx is 'delivering'. In real life somewhat less gets to the antenna.

Vic K2VCO /4X6GP

> On Jan 13, 2015, at 3:19 AM, Fred Jensen <[hidden email]> wrote:
>
> Well ... sort of. Some of the reflected power heats up the ATU and/or PA depending on the match it sees [actually, some of the forward power does too, tuners have forward losses]. "Delivered Power" is somewhat difficult to calculate. Working into a matched, non-reactive load [common for AM broadcast, at least a number of years ago], it's "I squared R" where R is the radiation resistance of the antenna ... and some minor conductor losses in the antenna. Things get pretty sticky if it's not a matched load.
>
> 73,
>
> Fred K6DGW
> - Northern California Contest Club
> - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
> - www.cqp.org
>
>> On 1/12/2015 4:46 PM, Phil & Debbie Salas wrote:
>>
>> Actually, "delivered power" is pretty much what you are measuring.
>> Remember that reflected power is re-reflected by the source and adds
>> back into the forward power. So in your example, you are transmitting
>> 1200 watts, having 200 watts reflected, then the 200 watts is
>> re-reflected by the source giving you the 1200 watts. Of course, there
>> will be transmission line SWR-related losses.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Vic Rosenthal

Re: Feature wanted for W2 wattmeter

In reply to this post by Vic Rosenthal

So why do I need an amplifier? I can just double my power by detuning my antenna tuner!

Vic K2VCO /4X6GP

> On Jan 13, 2015, at 6:54 AM, Walter Underwood <[hidden email]> wrote:
>
> All power ends in a load.
>
> Forward and reverse power measures standing waves, but all those waves go into some kind of load. Nearly all of it, if you are lucky, goes to the antenna. The rest goes to heat. Forward and reverse is just a way to measure standing waves. It does not mean the some percentage of “reverse power” is disappearing into your power amplifier.
>
> If you are running legal limit into forward power, you are quite likely running illegal power into the the antenna.
>
> I was happy to get a C+ in my fields and waves class at Rice, but I do understand this stuff.
>
> wunder
> K6WRU
> CM87wj
> http://observer.wunderwood.org/
>
>> On Jan 12, 2015, at 8:32 PM, Vic Rosenthal <[hidden email]> wrote:
>>
>> I'm talking about forward minus reflected power. If you neglect losses, that is how much power gets to the antenna to be radiated. A wattmeter that measures forward power will be misleading if the SWR is high. My antenna has an SWR of about 2.5:1 on 40 m. When the transmitter delivers 100 watts to the line, there is about 120 watts forward and 20 watts reflected. I want a mode in which the wattmeter reads 100 watts in this situation.
>>
>> Maybe 'delivered' is a bad choice of word. I mean something like 'power delivered by the transmitter'. Obviously it would take magic to know how much power gets to the antenna after losses!
>>
>> Vic K2VCO /4X6GP
>>
>>> On Jan 13, 2015, at 12:08 AM, Phil Hystad <[hidden email]> wrote:
>>>
>>> Vic,
>>>
>>> What do you mean by "delivered power"? I presume you mean delivered to the antenna (aka antenna system) but are you thinking power input to the W2 minus all the losses. By all losses I mean all losses on transmission line due to just plane old cable loss and higher losses due to higher SWR plus any loss in tuner or other devices between W2 and the aether.
>>>
>>> Because, due to conservation of energy, that RF energy either goes out into Electromagnetic waves (radiated) or it ends up as heat-loss somewhere in the system.
>>>
>>> And, given all that, I don't think any RF/SWR power meter on the market can measure "delivered power".
>>>
>>> Or, are you talking about something else.
>>>
>>> 73, phil, K7PEH
>>>
>>>
>>>> On Jan 12, 2015, at 11:31 AM, Vic Rosenthal 4X6GP/K2VCO <[hidden email]> wrote:
>>>>
>>>> I definitely want an LP100A, but I HAVE a W2, and while it is not as accurate, I still would like to see the delivered power!
>>>>
>>>>>> On 12 Jan 2015 21:12, Jim Brown wrote:
>>>>>> On Mon,1/12/2015 7:56 AM, Vic Rosenthal 4X6GP/K2VCO wrote:
>>>>>> I would like the W2 wattmeter to be able to display "delivered" power,
>>>>>> that is, forward power minus reflected power.
>>>>>
>>>>> You want N8LP's excellent LP-100A. I had lusted after one for quite a
>>>>> while, and bought W6OSP's unit after he died for about half price. The
>>>>> LP-100A supports two couplers, which can be deployed on the outputs of
>>>>> both transmitters in an SO2R setup, or on input and output of a power
>>>>> amp. The LP-100A measures the complex Z at the coupler, so it can
>>>>> measure the input Z of the amplifier under dynamic conditions.
>>>>>
>>>>> Now that I can measure power more accurately, I am able to run a dB or
>>>>> more closer to legal limit when I want to for contesting.
>>>>>
>>>>> 73, Jim K9YC
>>>>
>>>> --
>>>> 73,
>>>> Vic, 4X6GP/K2VCO
>>>> Rehovot, Israel
>>>> http://www.qsl.net/k2vco/
>>>> ______________________________________________________________
>>>> Elecraft mailing list
>>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>> Post: mailto:[hidden email]
>>>>
>>>> This list hosted by: http://www.qsl.net
>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>> Message delivered to [hidden email]
>>>
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Phil Wheeler-2

Re: Feature wanted for W2 wattmeter

Sounds like a plan, Vic :-)

BTW -- did you manage to get that antenna repaired?

73, Phil W7OX

On 1/12/15 9:09 PM, Vic Rosenthal wrote:

> So why do I need an amplifier? I can just double my power by detuning my antenna tuner!
>
> Vic K2VCO /4X6GP
>
>> On Jan 13, 2015, at 6:54 AM, Walter Underwood <[hidden email]> wrote:
>>
>> All power ends in a load.
>>
>> Forward and reverse power measures standing waves, but all those waves go into some kind of load. Nearly all of it, if you are lucky, goes to the antenna. The rest goes to heat. Forward and reverse is just a way to measure standing waves. It does not mean the some percentage of “reverse power” is disappearing into your power amplifier.
>>
>> If you are running legal limit into forward power, you are quite likely running illegal power into the the antenna.
>>
>> I was happy to get a C+ in my fields and waves class at Rice, but I do understand this stuff.
>>
>> wunder
>> K6WRU
>> CM87wj
>> http://observer.wunderwood.org/
>>
>>> On Jan 12, 2015, at 8:32 PM, Vic Rosenthal <[hidden email]> wrote:
>>>
>>> I'm talking about forward minus reflected power. If you neglect losses, that is how much power gets to the antenna to be radiated. A wattmeter that measures forward power will be misleading if the SWR is high. My antenna has an SWR of about 2.5:1 on 40 m. When the transmitter delivers 100 watts to the line, there is about 120 watts forward and 20 watts reflected. I want a mode in which the wattmeter reads 100 watts in this situation.
>>>
>>> Maybe 'delivered' is a bad choice of word. I mean something like 'power delivered by the transmitter'. Obviously it would take magic to know how much power gets to the antenna after losses!
>>>
>>> Vic K2VCO /4X6GP

Vic Rosenthal

Re: Feature wanted for W2 wattmeter

In reply to this post by Vic Rosenthal

Here is an experiment to show what I mean.
Take a transmitter and connect it to a 50 ohm dummy load through an antenna tuner. Put a wattmeter between the transmitter and the tuner.
Now adjust the transmitter for 100 watts output and the tuner for 1:1 SWR.
The meter reads 100W forward and zero reflected power.
Now adjust the tuner for an SWR of about 2.5:1. The wattmeter will show forward power of about 120 watts and reflected power of about 20 watts. Did I increase the real power output of my transmitter? Did I make my signal stronger? No.
I want a wattmeter that has an option to indicate 100 watts in this situation.

Vic K2VCO /4X6GP

> On Jan 13, 2015, at 6:56 AM, Walter Underwood <[hidden email]> wrote:
>
> No. That is wrong. Forward and reflected are aspects of the standing wave, not power delivered. —wunder, K6WRU
>
>> On Jan 12, 2015, at 8:53 PM, Vic Rosenthal <[hidden email]> wrote:
>>
>> What I want is just forward - reflected. Neglecting losses, this is what the tx is 'delivering'. In real life somewhat less gets to the antenna.
>>
>> Vic K2VCO /4X6GP
>>
>>> On Jan 13, 2015, at 3:19 AM, Fred Jensen <[hidden email]> wrote:
>>>
>>> Well ... sort of. Some of the reflected power heats up the ATU and/or PA depending on the match it sees [actually, some of the forward power does too, tuners have forward losses]. "Delivered Power" is somewhat difficult to calculate. Working into a matched, non-reactive load [common for AM broadcast, at least a number of years ago], it's "I squared R" where R is the radiation resistance of the antenna ... and some minor conductor losses in the antenna. Things get pretty sticky if it's not a matched load.
>>>
>>> 73,
>>>
>>> Fred K6DGW
>>> - Northern California Contest Club
>>> - CU in the 50th Running of the Cal QSO Party 3-4 Oct 2015
>>> - www.cqp.org
>>>
>>>> On 1/12/2015 4:46 PM, Phil & Debbie Salas wrote:
>>>>
>>>> Actually, "delivered power" is pretty much what you are measuring.
>>>> Remember that reflected power is re-reflected by the source and adds
>>>> back into the forward power. So in your example, you are transmitting
>>>> 1200 watts, having 200 watts reflected, then the 200 watts is
>>>> re-reflected by the source giving you the 1200 watts. Of course, there
>>>> will be transmission line SWR-related losses.
>>>
>>> ______________________________________________________________
>>> Elecraft mailing list
>>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>>> Help: http://mailman.qth.net/mmfaq.htm
>>> Post: mailto:[hidden email]
>>>
>>> This list hosted by: http://www.qsl.net
>>> Please help support this email list: http://www.qsl.net/donate.html
>>> Message delivered to [hidden email]
>> ______________________________________________________________
>> Elecraft mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/elecraft
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:[hidden email]
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>> Message delivered to [hidden email]
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

David Woolley (E.L)

Re: Feature wanted for W2 wattmeter

In reply to this post by k6dgw

As well as not all the reflected power being re-reflected, the forward
power measured by the coupler is not the first time forward power, but
the sum of all the re-reflected power, as well.

--
David Woolley
Owner K2 06123

On 13/01/15 01:19, Fred Jensen wrote:
> Well ... sort of. Some of the reflected power heats up the ATU and/or
> PA depending on the match it sees [actually, some of the forward power
> does too, tuners have forward losses]. "Delivered Power" is somewhat

>
> On 1/12/2015 4:46 PM, Phil & Debbie Salas wrote:
>
>> Actually, "delivered power" is pretty much what you are measuring.
>> Remember that reflected power is re-reflected by the source and adds
>> back into the forward power. So in your example, you are transmitting
>> 1200 watts, having 200 watts reflected, then the 200 watts is
>> re-reflected by the source giving you the 1200 watts. Of course, there
>> will be transmission line SWR-related losses.
>
>

Myron WVØH

Re: Feature wanted for W2 wattmeter

Since this has historically been a can of worms, (it created a firestorm of emails back in 2010 on a yahoo group between W5DXB, R. Fry, K1TTT, W7EL, and Owen Duffy, then VK1OD) I want to introduce an authority on power measurement. Agilent (now called Keysight) has a three part document that talks about power measurement, the usefulness of these documents depends upon your level of understanding and application but since we can all add and subtract, eqn 2-21 of this document indicates that the power delivered to the load (with all of the assumptions listed) is the forward (incident) power minus the reflected power.

http://cp.literature.agilent.com/litweb/pdf/5988-9215EN.pdf

Myron WVØH
Printed on Recycled Data

> On Jan 13, 2015, at 1:45 AM, David Woolley <[hidden email]> wrote:
>
> As well as not all the reflected power being re-reflected, the forward power measured by the coupler is not the first time forward power, but the sum of all the re-reflected power, as well.
>
> --
> David Woolley
> Owner K2 06123
>
>> On 13/01/15 01:19, Fred Jensen wrote:
>> Well ... sort of. Some of the reflected power heats up the ATU and/or
>> PA depending on the match it sees [actually, some of the forward power
>> does too, tuners have forward losses]. "Delivered Power" is somewhat
>
>>
>>> On 1/12/2015 4:46 PM, Phil & Debbie Salas wrote:
>>>
>>> Actually, "delivered power" is pretty much what you are measuring.
>>> Remember that reflected power is re-reflected by the source and adds
>>> back into the forward power. So in your example, you are transmitting
>>> 1200 watts, having 200 watts reflected, then the 200 watts is
>>> re-reflected by the source giving you the 1200 watts. Of course, there
>>> will be transmission line SWR-related losses.
>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]

Alan Bloom

Re: Feature wanted for W2 wattmeter

In reply to this post by David Woolley (E.L)

The power delivered to the load really is forward power minus reverse
power. You can see that by imagining that you disconnect the load
completely (infinite impedance) or short it out (zero impedance). That
means no power can be absorbed by the load.

The wattmeter reads equal forward and reverse power, so that forward
minus reverse equals zero, as it must.

Alan N1AL

On 01/13/2015 12:45 AM, David Woolley wrote:
> As well as not all the reflected power being re-reflected, the forward
> power measured by the coupler is not the first time forward power, but
> the sum of all the re-reflected power, as well.
>

______________________________________________________________
Elecraft mailing list
Home: http://mailman.qth.net/mailman/listinfo/elecraft
Help: http://mailman.qth.net/mmfaq.htm
Post: mailto:[hidden email]

This list hosted by: http://www.qsl.net
Please help support this email list: http://www.qsl.net/donate.html
Message delivered to [hidden email]

Carey Magee

Re: Feature wanted for W2 wattmeter

Hi Folks:

Been reading this thread and just wanted to mention that the Elecraft W2
Interface program (
http://www.elecraft.com/software/W2/elecraft_w2_software.htm) shows both
forward and reflected power quite nicely.

73,
Carey, K2RNY
Rochester New York
Grid: FN13ef

On Tue, Jan 13, 2015 at 2:48 PM, Alan <[hidden email]> wrote:

> The power delivered to the load really is forward power minus reverse
> power. You can see that by imagining that you disconnect the load
> completely (infinite impedance) or short it out (zero impedance). That
> means no power can be absorbed by the load.
>
> The wattmeter reads equal forward and reverse power, so that forward minus
> reverse equals zero, as it must.
>
> Alan N1AL
>
>
>
> On 01/13/2015 12:45 AM, David Woolley wrote:
>
>> As well as not all the reflected power being re-reflected, the forward
>> power measured by the coupler is not the first time forward power, but the
>> sum of all the re-reflected power, as well.
>>
>>
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html
> Message delivered to [hidden email]
>

Vic Rosenthal

Re: Feature wanted for W2 wattmeter

And I started this thread by pointing that out, and saying "wouldn't it
be nice if the W2 firmware could show Pf - Pr in the LED display." I
don't have screen space for yet another application.

On 13 Jan 2015 22:11, Carey Magee wrote:

> Hi Folks:
>
> Been reading this thread and just wanted to mention that the Elecraft W2
> Interface program (
> http://www.elecraft.com/software/W2/elecraft_w2_software.htm) shows both
> forward and reflected power quite nicely.
>
> 73,
> Carey, K2RNY
> Rochester New York
> Grid: FN13ef
>
> On Tue, Jan 13, 2015 at 2:48 PM, Alan <[hidden email]> wrote:
>
>> The power delivered to the load really is forward power minus reverse
>> power. You can see that by imagining that you disconnect the load
>> completely (infinite impedance) or short it out (zero impedance). That
>> means no power can be absorbed by the load.
>>
>> The wattmeter reads equal forward and reverse power, so that forward minus
>> reverse equals zero, as it must.
>>
>> Alan N1AL
>>
>>
>>
>> On 01/13/2015 12:45 AM, David Woolley wrote:
>>
>>> As well as not all the reflected power being re-reflected, the forward
>>> power measured by the coupler is not the first time forward power, but the
>>> sum of all the re-reflected power, as well.