Topics

Power Meter

Alfredo Mendiola Loyola
 

Hello,

I would like to buy a power meter to calibrate my AD8307

Is there a power meter that doens't require anual Calibration.

I line in Peru and it is expensive to send the power meter to US just for anual calibration like the Power Meter 6G of Minicircuits.

73
Alfredo.

Pravin
 

Hi Alfredo,
It will be a over kill to purchase a power enter for calibration of AD8307 chip meter . If you have an access for an Oscilloscope and having a carbon resistor for 51 Ohms you can simply measure the voltage across the resistor and compare it with your Ad8307 chip values .
Power = Square of Vrms/50 . Nothing will be more precise than that and no need of sending power meters to be calibrated in US every now and then .

--------------------------------------------

On Mon, 5/7/18, Alfredo Mendiola Loyola via Groups.Io <mendiola_loyola=yahoo.com@groups.io> wrote:

Subject: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Monday, May 7, 2018, 5:51 PM

Hello,

I would like to buy a power meter to
calibrate my AD8307

Is there a power meter that doens't
require anual Calibration.

I line in Peru and it is expensive to
send the power meter to US just for anual calibration like
the Power Meter 6G of Minicircuits.

73
Alfredo.

Alfredo Mendiola Loyola
 

Do Oscilloscopes require calibration each n years?

73
Alfredo
OA4AJP

Pravin
 

Yes every measurement device require periodic calibration . But in my long long experience the standard test equipments manufactured my HP, R&S, Marconi, Anritsu etc maintain the calibrations for long long time . Actually if you are not a precision manufacture of systems these equipments are good for long time.
(Pravin)

--------------------------------------------

On Mon, 5/7/18, Alfredo Mendiola Loyola via Groups.Io <mendiola_loyola=yahoo.com@groups.io> wrote:

Subject: Re: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Monday, May 7, 2018, 6:24 PM

Do Oscilloscopes require
calibration each n years?

73
Alfredo
OA4AJP

dick faust
 

Sam Wetterlin has some information on his web site on how to build a calibrator and the theory behind the circuit. It is the fifth paragraph down, under the title "MSA Documentation Relating to Hardware" http://www.wetterlin.org/sam/

I made a version for myself and there is documentation on my web page along with Gerbers for OSH Park under "Calibration Source for VNA, PHSNA, Scopes or Spectrum Analyzers" http://www.k9ivb.net/VNA/index.htm

There was also a spreadsheet and documentation in the old Yahoo Groups File area [not sure where it is here] on how to calibrate with a battery and a pot by applying the DC directly to the AD8307 inputs.

Dick K9IVB

Nick Kennedy
 

To calibrate, you need a sine wave source of known power level and a step
attenuator. Actually, a single attenuator would work but it's better to
have multiple points. There's information in the User's Guide and the
software has a built-in function for power calibration.

The source should have a frequency somewhere in "midrange" - perhaps 5 to
15 MHz.

I homebrewed two simple sources for my calibration. First was the -10 dBm
square wave calibrator by Bob Kopshi K3NHI and a 10 dBm, 10 MHz sinewave
calibrator by VE7BPO that I calibrated to K3NHI's circuit. I used a
homebrew step attenuator. Attenuators are pretty cheap and easy to build

You can find some folders in the Files area that describe how people did
calibrations. The circuits and articles I described can be found on the
web. I can provide some of the articles and circuits if needed.

Other suggestions I've heard here also sound good.

73-

Nick, WA5BDU

On Mon, May 7, 2018 at 4:51 PM Alfredo Mendiola Loyola via Groups.Io
<mendiola_loyola=yahoo.com@groups.io> wrote:

Hello,

I would like to buy a power meter to calibrate my AD8307

Is there a power meter that doens't require anual Calibration.

I line in Peru and it is expensive to send the power meter to US just for
anual calibration like the Power Meter 6G of Minicircuits.

73
Alfredo.



Steven Dick
 

I don't know how accurate you are trying to get but if you are within say three percent, that is usually more than accurate. A scope is a good way to perform an accurate measurement, but scope calibration is always the limiting factor, and most hams don't bother with periodic accurate calibration of their scope. You could make your own fairly accurate homebrew relatively low cost calibrator based on a precision reference such as the Analog Devices ADR03-EP, a 10 volt reference with initial accuracy of 0.2 percent for $5.15 or the TI REF102 with an accuracy of +10V +/- 0.0025V for $5.02. I've been meaning to build a precision reference using one of these just for a calibration sanity check of my scope.

-Steve K1RF

-----Original Message-----
From: Pravin via Groups.Io
Sent: Monday, May 07, 2018 6:53 PM
To: PHSNA@groups.io
Subject: Re: [PHSNA] Power Meter

Yes every measurement device require periodic calibration . But in my long long experience the standard test equipments manufactured my HP, R&S, Marconi, Anritsu etc maintain the calibrations for long long time . Actually if you are not a precision manufacture of systems these equipments are good for long time.
(Pravin)

--------------------------------------------
On Mon, 5/7/18, Alfredo Mendiola Loyola via Groups.Io <mendiola_loyola=yahoo.com@groups.io> wrote:

Subject: Re: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Monday, May 7, 2018, 6:24 PM

Do Oscilloscopes require
calibration each n years?

73
Alfredo
OA4AJP

Philippe CREIS
 

Hi all,

i think using a scope is not a good solution at all. Measuring a voltage with an oscilloscope is a good idea. Provided you know the subtleties of this device. An oscilloscope becomes very quickly false, even very false in the measurement of a voltage. Look at this excerpt from an article published by Yokogawa, and this is true for all the scopes:
"The analogue bandwidth is defined as the frequency at which the amplitude measured by the oscilloscope has reduced by 3dB (-3dB point). This is approximately 70.9% of the actual signal amplitude (Figure 1). This means, for example, if a 200MHz pure sine wave with 10 Volts peak to peak is measured with an oscilloscope with a bandwidth of 200MHz, the amplitude of the displayed signal will be approximately 7 Volts peak to peak."

So, if you want to calibrate your wattmeter based on an AD8307 with an oscilloscope on 430MHz, you will have to find a very, very expensive oscilloscope !!!! Look rather on the side of the references of power, to realize yourself, it will be much more precise.

--
73... Philippe - F4GRT

Message du 08/05/18 00:19
De : "Pravin via Groups.Io"
A : PHSNA@groups.io
Copie à :
Objet : Re: [PHSNA] Power Meter

Hi Alfredo,
It will be a over kill to purchase a power enter for calibration of AD8307 chip meter . If you have an access for an Oscilloscope and having a carbon resistor for 51 Ohms you can simply measure the voltage across the resistor and compare it with your Ad8307 chip values .
Power = Square of Vrms/50 . Nothing will be more precise than that and no need of sending power meters to be calibrated in US every now and then .

--------------------------------------------
On Mon, 5/7/18, Alfredo Mendiola Loyola via Groups.Io wrote:

Subject: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Monday, May 7, 2018, 5:51 PM

Hello,

I would like to buy a power meter to
calibrate my AD8307

Is there a power meter that doens't
require anual Calibration.

I line in Peru and it is expensive to
send the power meter to US just for anual calibration like
the Power Meter 6G of Minicircuits.

73
Alfredo.






Steven Dick
 

Quite correct. If you need the amplitude to be accurate to ~1%, you need to
derate your scope by a factor of 0.1x, meaning that on your 100MHz scope you
can only capture 10MHz with a 1% error in amplitude. If you reduce this
reqquirement to 3% accuracy, you need to derate it by a factor of ~0.3x, so
a 100MHz scope can accurately measure 30MHz to 3%.

-----Original Message-----
From: Philippe CREIS
Sent: Tuesday, May 08, 2018 4:02 PM
To: PHSNA@groups.io
Subject: Re: [PHSNA] Power Meter

Hi all,

i think using a scope is not a good solution at all. Measuring a voltage
with an oscilloscope is a good idea. Provided you know the subtleties of
this device. An oscilloscope becomes very quickly false, even very false in
the measurement of a voltage. Look at this excerpt from an article published
by Yokogawa, and this is true for all the scopes:
"The analogue bandwidth is defined as the frequency at which the amplitude
measured by the oscilloscope has reduced by 3dB (-3dB point). This is
approximately 70.9% of the actual signal amplitude (Figure 1). This means,
for example, if a 200MHz pure sine wave with 10 Volts peak to peak is
measured with an oscilloscope with a bandwidth of 200MHz, the amplitude of
the displayed signal will be approximately 7 Volts peak to peak."

So, if you want to calibrate your wattmeter based on an AD8307 with an
oscilloscope on 430MHz, you will have to find a very, very expensive
oscilloscope !!!! Look rather on the side of the references of power, to
realize yourself, it will be much more precise.

--
73... Philippe - F4GRT




Message du 08/05/18 00:19
De : "Pravin via Groups.Io"
A : PHSNA@groups.io
Copie à :
Objet : Re: [PHSNA] Power Meter

Hi Alfredo,
It will be a over kill to purchase a power enter for calibration of AD8307
chip meter . If you have an access for an Oscilloscope and having a carbon
resistor for 51 Ohms you can simply measure the voltage across the
resistor and compare it with your Ad8307 chip values .
Power = Square of Vrms/50 . Nothing will be more precise than that and no
need of sending power meters to be calibrated in US every now and then .

--------------------------------------------
On Mon, 5/7/18, Alfredo Mendiola Loyola via Groups.Io wrote:

Subject: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Monday, May 7, 2018, 5:51 PM

Hello,

I would like to buy a power meter to
calibrate my AD8307

Is there a power meter that doens't
require anual Calibration.

I line in Peru and it is expensive to
send the power meter to US just for anual calibration like
the Power Meter 6G of Minicircuits.

73
Alfredo.






Alfredo Mendiola Loyola
 

Steven,

The ADR03-EP gives dc voltage, I think we need a sine wave reference to calibrate our RF equipment.

73
Alfred.

Steven Dick
 

The DC reference is fine. Yu can then switch to AC, assuming there is no error in switching from DC to AC in amplitude. But AC amplitude accuracy will depend on scope bandwidth vs measured signal bandwidth under test. For good accuracy, the scope should have ~10X the bandwidth of the highest frequency being measured.

-----Original Message-----
From: Alfredo Mendiola Loyola via Groups.Io
Sent: Tuesday, May 08, 2018 4:22 PM
To: PHSNA@groups.io
Subject: Re: [PHSNA] Power Meter

Steven,

The ADR03-EP gives dc voltage, I think we need a sine wave reference to calibrate our RF equipment.

73
Alfred.

Pravin
 

Hi Philppe,
Yes you are correct . But here we are talking about HF ( up to 30 MHz) only . So if we can get a scope with bandwidth up to 60 MHz it will be good for our purpose. I haven't seen a modern scope below that bandwidth . So almost any school or even "makerspace" labs will have such scopes. And we need not own such a scope as it is required only once in an year or so for confirmation of calibrations. Hope this helps .
(Pravin)
AB9XC

--------------------------------------------

On Tue, 5/8/18, Philippe CREIS <Philippe.Creis@...> wrote:

Subject: Re: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Tuesday, May 8, 2018, 4:02 PM

Hi all,

i think using a scope is not a good solution at
all. Measuring a voltage with an oscilloscope is a good
idea. Provided you know the subtleties of this device. An
oscilloscope becomes very quickly false, even very false in
the measurement of a voltage. Look at this excerpt from an
article published by Yokogawa, and this is true for all the
scopes:
"The analogue bandwidth is
defined as the frequency at which the amplitude measured by
the oscilloscope has reduced by 3dB (-3dB point). This is
approximately 70.9% of the actual signal amplitude (Figure
1). This means, for example, if a 200MHz pure sine wave with
10 Volts peak to peak is measured with an oscilloscope with
a bandwidth of 200MHz, the amplitude of the displayed signal
will be approximately 7 Volts peak to peak."

So, if you want to calibrate
your wattmeter based on an AD8307 with an oscilloscope on
430MHz, you will have to find a very, very expensive
oscilloscope !!!! Look rather on the side of the references
of power, to realize yourself, it will be much more
precise.

--
73... Philippe - F4GRT
 
 
 
 
> Message du 08/05/18 00:19
> De : "Pravin via Groups.Io"
> A : PHSNA@groups.io
> Copie à :
> Objet :
Re: [PHSNA] Power Meter
>
> Hi Alfredo,
> It will
be a over kill to purchase a power enter for calibration of
AD8307 chip meter . If you have an access for an
Oscilloscope and having a carbon resistor for 51 Ohms you
can simply measure the voltage across the resistor and
compare it with your Ad8307 chip values .
> Power = Square of Vrms/50 . Nothing will
be more precise than that and no need of sending power
meters to be calibrated in US every now and then .
>
>
--------------------------------------------
> On Mon, 5/7/18, Alfredo Mendiola Loyola
via Groups.Io  wrote:
>
> Subject: [PHSNA] Power Meter
> To: PHSNA@groups.io
> Date: Monday, May 7, 2018, 5:51 PM
>
> Hello,
>
> I would like to buy
a power meter to
> calibrate my AD8307
>
> Is there a power
meter that doens't
> require anual
Calibration.
>
> I
line in Peru and it is expensive to
>
send the power meter to US just for anual calibration
like
> the Power Meter 6G of
Minicircuits.
>
>
73
> Alfredo.
>
>
>
>
>
>
>

Nick Kennedy
 

Most people do a power calibration on their PHSNA system at a "mid-range"
frequency like 10 MHz but do not do one over the expected frequency range
of the detector. A well calibrated scope is adequate for that (mid-range)
purpose.

The high end of the complete system is about 30 or 60 MHz depending on
which DDS is used.

If well constructed, the detector used alone can be reasonably flat up to
about 500 MHz, per Hayward and Larkin. I haven't had the equipment to
validate that, however. I expect it's OK up through 2 meters. without much
doubt.

I recently bought a used Fluke 6060A/AN signal generator at a great price.
It's 1980s technology and not at all state of the art. But I used it to
check the response of my AD8307 detector yesterday, from 10 MHz though 300
MHz at -10 dBm input. Referred to the reading at 10 MHz, it was down 0.8 dB
at 100 MHz and 1.8 dB at 300 MHz. Again, the signal generator itself isn't
super accurate, but I felt that this was a good validation that the
detector is working as it should.

73-

Nick, WA5BDU



On Tue, May 8, 2018 at 3:02 PM Philippe CREIS <Philippe.Creis@...>
wrote:

Hi all,

i think using a scope is not a good solution at all. Measuring a voltage
with an oscilloscope is a good idea. Provided you know the subtleties of
this device. An oscilloscope becomes very quickly false, even very false in
the measurement of a voltage. Look at this excerpt from an article
published by Yokogawa, and this is true for all the scopes:
"The analogue bandwidth is defined as the frequency at which the amplitude
measured by the oscilloscope has reduced by 3dB (-3dB point). This is
approximately 70.9% of the actual signal amplitude (Figure 1). This means,
for example, if a 200MHz pure sine wave with 10 Volts peak to peak is
measured with an oscilloscope with a bandwidth of 200MHz, the amplitude of
the displayed signal will be approximately 7 Volts peak to peak."

So, if you want to calibrate your wattmeter based on an AD8307 with an
oscilloscope on 430MHz, you will have to find a very, very expensive
oscilloscope !!!! Look rather on the side of the references of power, to
realize yourself, it will be much more precise.

--
73... Philippe - F4GRT




Message du 08/05/18 00:19
De : "Pravin via Groups.Io"
A : PHSNA@groups.io
Copie à :
Objet : Re: [PHSNA] Power Meter

Hi Alfredo,
It will be a over kill to purchase a power enter for calibration of
AD8307 chip meter . If you have an access for an Oscilloscope and having a
carbon resistor for 51 Ohms you can simply measure the voltage across the
resistor and compare it with your Ad8307 chip values .
Power = Square of Vrms/50 . Nothing will be more precise than that and
no need of sending power meters to be calibrated in US every now and then .

--------------------------------------------
On Mon, 5/7/18, Alfredo Mendiola Loyola via Groups.Io wrote:

Subject: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Monday, May 7, 2018, 5:51 PM

Hello,

I would like to buy a power meter to
calibrate my AD8307

Is there a power meter that doens't
require anual Calibration.

I line in Peru and it is expensive to
send the power meter to US just for anual calibration like
the Power Meter 6G of Minicircuits.

73
Alfredo.








DuWayne Schmidlkofer
 

I have had good luck with a RF power reference I built based on the one at W1GHZ.ORG. That and a step attenuator has been adequate for calibration of the AD8307 for general amateur radio use. Of course if you are using the power meter for commercial applications you may have to have it calibrated by a service that has a traceable standards.
DuWayne KV4QB

On 5/7/2018 5:51 PM, Alfredo Mendiola Loyola via Groups.Io wrote:
Hello,
I would like to buy a power meter to calibrate my AD8307
Is there a power meter that doens't require anual Calibration.
I line in Peru and it is expensive to send the power meter to US just for anual calibration like the Power Meter 6G of Minicircuits.
73
Alfredo.

David Collins
 

Hi Alfredo and the group,

Check this out and save some $$$.

http://sp-hm.pl/attachment.php?aid=13774

We use this technique in the MSNA and it works very good.


73,
Dave Collins - AD7JT

Nick Kennedy
 

I also used that circuit by Bob Kopski K3NHI for my calibration.

Note that some years after the article appeared in QEX, the author
discovered that currently manufactured AD8307 chips no longer responded the
same way when a square wave was applied, at least not over the full range
of inputs. It turns out the relationship still applied at -10 dBm but might
deviate at -20 dBm, so he released a revised schematic of his calibrator
that outputs the equivalent of -10 dBm.

I just browsed our Files section for the paper describing the issue and the
revised schematic, but didn't find them. So, I've uploaded them to my
WA5BDU folder in the group's Files section. The discussion is in "AN AD8307
ADVISORY - K3NHI.rtf", and the new schematic is in "RF POWER CALIBRATOR II
- Kopski.pdf".

73-

Nick, WA5BDU

On Wed, May 9, 2018 at 9:21 AM David Collins <ad7jt@...> wrote:

Hi Alfredo and the group,

Check this out and save some $$$.

http://sp-hm.pl/attachment.php?aid=13774

We use this technique in the MSNA and it works very good.


73,
Dave Collins - AD7JT




Alfredo Mendiola Loyola
 

I have decided to buy a Spectrum Analyzer https://www.rigolna.com/products/spectrum-analyzers/dsa700/

It has 500 mhz of bandwidth and 5% of accuracy for dBm measurements. (+/-0.25dB)

I hope it doesn't require anual calibrations.

73
OA4AJP
Alfredo.

Pravin
 

Hi Alfredo,
You may confirm the same with the company before you order it. In my long career as an Electronics Engineer I haven't come across any test equipment that does not require periodic re-calibration. Most of them are good for one year but some for 3 years. Once again the re-calibration is required only if you want precision accuracy traceable against primary standards. That is usually the case with high precision manufacturing like space, defense , cellphone etc. I think for HAM use one need not spend money for annual re-calibration.

73
DE AB9XC
(Pravin)

--------------------------------------------

On Fri, 5/11/18, Alfredo Mendiola Loyola via Groups.Io <mendiola_loyola=yahoo.com@groups.io> wrote:

Subject: Re: [PHSNA] Power Meter
To: PHSNA@groups.io
Date: Friday, May 11, 2018, 1:54 PM

I have decided to buy a Spectrum
Analyzer  https://www.rigolna.com/products/spectrum-analyzers/dsa700/

It has 500 mhz of bandwidth
and 5% of accuracy for dBm measurements. (+/-0.25dB)

I hope it doesn't require
anual calibrations.

73
OA4AJP
Alfredo.

Joerg - exDB2OO
 

There is a very nice power calibrator design available from a German ham. Just google for "dl7av calibration". Use a translator, to translate the German text. It creates a 0 dBm sine output. I built it myself (cost approx. 10 EUR) and the harmonics are >30 dB suppressed.

Hans Summers
 

Hi JoergU

There is a very nice power calibrator design available from a German ham.
Just google for "dl7av calibration". Use a translator, to translate the
German text.
It creates a 0 dBm sine output. I built it myself (cost approx. 10 EUR)
and the
harmonics are >30 dB suppressed.
Many thanks for this. Very rare for this to happen, but it happened to be
exactly WHAT I needed and WHEN I needed it... so I googled DL7AV
calibration and found several pages, of which the main one I followed was
http://dl6gl.de/station/selbstregelnder-kurzwellen-kalibrierungsgenerator

So I built my own version from entirely junkbox parts yesterday afternoon
and I have made a YouTube video about it see https://youtu.be/732ESoul088

This will be very useful in my case - thanks again!

73 Hans G0UPL
http://qrp-labs.com