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HP 8920A spectrum analyser amplitude calibration

 

Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

Hi Colin

I have also seen your posting on the HP8924 group which has additional information in it.

First it is very important to say at what frequencies you are experiencing the errors, the main reason for this is that the front panel on a HP8920A gives the operating range as 400KHz to 1GHz. This is ONLY true for the original electromechanical attenuator version, all the ones that I have seen in the UK have had the PIN diode attenuator fitted which in my experience cannot be trusted below 50MHz. HP claimed 10MHz in their dreams.

Most of these test sets were purchased in the UK for analogue cellular use so the use of a PIN diode attenuator was not an issue.

I would first check to see if the input load measures 50 ohms at the N port, if it does then check and re torque the internal hard line SMA's using a torque spanner, this is very important to avoid damage to the SMA's. There were a number of optimal power handling input loads available, it is not unknown for excess RF power to damage them.

I have not had to work on a 8920A for some years, but as I recall the calibration/adjustment was carried out via the GPIB port using dedicated HP software that would not run on anything later than Windows 95 or possibly 98.

Hope that this helps

George G6HIG
On Sunday, 12 April 2020, 22:18:40 BST, Colin Smithers <colin@...> wrote:


Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

开云体育

Hi George,

?

Just measured, the unit is substantially flat (+/-0.2dB) across the range from 1MHz -500MHz, but with the Main input around -2.2dB and Ant input -2.6dB. But these back my point that for a subsidiary function this Spec An is very good indeed.

?

The Main input shows >-25dB return loss, I am yet to measure the Ant input.

?

Looking at the Spec An block diagram two things stick out:-

?

-????????? A signal switch near the front with a Cal setting

-????????? A 4-in-1 DAC which seems to control variable gain amp as well as IF filters

?

So I remain thinking that ?I’m on the hunt for a deeply buried Cal routine. Fiddling with loss internally is clearly possible (from another rreply), but only finding the routine would be future proof.

?

Thanks for info about that HP IEEE 488 program. My Win95 machine does still boot up…?? J Gonna have to find an IEEE488 card though. Or info on what the code drives.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]] On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 00:37
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I have also seen your posting on the HP8924 group which has additional information in it.

First it is very important to say at what frequencies you are experiencing the errors, the main reason for this is that the front panel on a HP8920A gives the operating range as 400KHz to 1GHz. This is ONLY true for the original electromechanical attenuator version, all the ones that I have seen in the UK have had the PIN diode attenuator fitted which in my experience cannot be trusted below 50MHz. HP claimed 10MHz in their dreams.

Most of these test sets were purchased in the UK for analogue cellular use so the use of a PIN diode attenuator was not an issue.

I would first check to see if the input load measures 50 ohms at the N port, if it does then check and re torque the internal hard line SMA's using a torque spanner, this is very important to avoid damage to the SMA's. There were a number of optimal power handling input loads available, it is not unknown for excess RF power to damage them.

I have not had to work on a 8920A for some years, but as I recall the calibration/adjustment was carried out via the GPIB port using dedicated HP software that would not run on anything later than Windows 95 or possibly 98.

Hope that this helps

George G6HIG

On Sunday, 12 April 2020, 22:18:40 BST, Colin Smithers <colin@...> wrote:

?

?

Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

Hi Colin

I do not understand the posting about making manual adjustments, I can see that using the suggested approach for fault finding is valid, but not for adjusting the calibration given that the 8920A is software calibrated only. The calibration constants are held in none volatile memory in each module which are read into main ram on power up.

As far as I remember the Cal switch just enables and disables the ability to carry out a calibration via the GPIB port.

Prior to 1999 all 8920A's had a mechanical attenuator, which your appears to have. It then became option 055 with the PIN diode attenuator as option 009.

The only remaining commercial support for the 8920A is provided by Amtronix in the US, who do provide full repair and calibration facilities for them.

Are you aware of the information at Amtronix.com/diagnostic/htm?

Do you have the CLIP for the 8920A, I do if you need it.

Regards

George G6HIG
On Monday, 13 April 2020, 07:25:14 BST, Colin Smithers <colin@...> wrote:


Hi George,

?

Just measured, the unit is substantially flat (+/-0.2dB) across the range from 1MHz -500MHz, but with the Main input around -2.2dB and Ant input -2.6dB. But these back my point that for a subsidiary function this Spec An is very good indeed.

?

The Main input shows >-25dB return loss, I am yet to measure the Ant input.

?

Looking at the Spec An block diagram two things stick out:-

?

-?????????A signal switch near the front with a Cal setting

-?????????A 4-in-1 DAC which seems to control variable gain amp as well as IF filters

?

So I remain thinking that ?I’m on the hunt for a deeply buried Cal routine. Fiddling with loss internally is clearly possible (from another rreply), but only finding the routine would be future proof.

?

Thanks for info about that HP IEEE 488 program. My Win95 machine does still boot up…??J Gonna have to find an IEEE488 card though. Or info on what the code drives.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 00:37
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I have also seen your posting on the HP8924 group which has additional information in it.

First it is very important to say at what frequencies you are experiencing the errors, the main reason for this is that the front panel on a HP8920A gives the operating range as 400KHz to 1GHz. This is ONLY true for the original electromechanical attenuator version, all the ones that I have seen in the UK have had the PIN diode attenuator fitted which in my experience cannot be trusted below 50MHz. HP claimed 10MHz in their dreams.

Most of these test sets were purchased in the UK for analogue cellular use so the use of a PIN diode attenuator was not an issue.

I would first check to see if the input load measures 50 ohms at the N port, if it does then check and re torque the internal hard line SMA's using a torque spanner, this is very important to avoid damage to the SMA's. There were a number of optimal power handling input loads available, it is not unknown for excess RF power to damage them.

I have not had to work on a 8920A for some years, but as I recall the calibration/adjustment was carried out via the GPIB port using dedicated HP software that would not run on anything later than Windows 95 or possibly 98.

Hope that this helps

George G6HIG

On Sunday, 12 April 2020, 22:18:40 BST, Colin Smithers <colin@...> wrote:

?

?

Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

开云体育

Hi George,

?

Now were motoring! I was unaware of Amtronix, thanks. Clearly they must know and perhaps might help.

?

You will have to inlighten me as to what the CLIP is, please?

?

Kind regards

?

Colin

?

From: [email protected] [mailto:[email protected]] On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 10:32
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I do not understand the posting about making manual adjustments, I can see that using the suggested approach for fault finding is valid, but not for adjusting the calibration given that the 8920A is software calibrated only. The calibration constants are held in none volatile memory in each module which are read into main ram on power up.

As far as I remember the Cal switch just enables and disables the ability to carry out a calibration via the GPIB port.

Prior to 1999 all 8920A's had a mechanical attenuator, which your appears to have. It then became option 055 with the PIN diode attenuator as option 009.

The only remaining commercial support for the 8920A is provided by Amtronix in the US, who do provide full repair and calibration facilities for them.

Are you aware of the information at Amtronix.com/diagnostic/htm?

Do you have the CLIP for the 8920A, I do if you need it.

Regards

George G6HIG

On Monday, 13 April 2020, 07:25:14 BST, Colin Smithers <colin@...> wrote:

?

?

Hi George,

?

Just measured, the unit is substantially flat (+/-0.2dB) across the range from 1MHz -500MHz, but with the Main input around -2.2dB and Ant input -2.6dB. But these back my point that for a subsidiary function this Spec An is very good indeed.

?

The Main input shows >-25dB return loss, I am yet to measure the Ant input.

?

Looking at the Spec An block diagram two things stick out:-

?

-?????????A signal switch near the front with a Cal setting

-?????????A 4-in-1 DAC which seems to control variable gain amp as well as IF filters

?

So I remain thinking that ?I’m on the hunt for a deeply buried Cal routine. Fiddling with loss internally is clearly possible (from another rreply), but only finding the routine would be future proof.

?

Thanks for info about that HP IEEE 488 program. My Win95 machine does still boot up…??J Gonna have to find an IEEE488 card though. Or info on what the code drives.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 00:37
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I have also seen your posting on the HP8924 group which has additional information in it.

First it is very important to say at what frequencies you are experiencing the errors, the main reason for this is that the front panel on a HP8920A gives the operating range as 400KHz to 1GHz. This is ONLY true for the original electromechanical attenuator version, all the ones that I have seen in the UK have had the PIN diode attenuator fitted which in my experience cannot be trusted below 50MHz. HP claimed 10MHz in their dreams.

Most of these test sets were purchased in the UK for analogue cellular use so the use of a PIN diode attenuator was not an issue.

I would first check to see if the input load measures 50 ohms at the N port, if it does then check and re torque the internal hard line SMA's using a torque spanner, this is very important to avoid damage to the SMA's. There were a number of optimal power handling input loads available, it is not unknown for excess RF power to damage them.

I have not had to work on a 8920A for some years, but as I recall the calibration/adjustment was carried out via the GPIB port using dedicated HP software that would not run on anything later than Windows 95 or possibly 98.

Hope that this helps

George G6HIG

On Sunday, 12 April 2020, 22:18:40 BST, Colin Smithers <colin@...> wrote:

?

?

Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

开云体育

CLIP == Component Level Information Pack == Schematics and Parts Lists (no sorry no Theory of Operation sections)

?

David

?

From: [email protected] [mailto:[email protected]] On Behalf Of Colin Smithers
Sent: 13 April 2020 11:28
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi George,

?

Now were motoring! I was unaware of Amtronix, thanks. Clearly they must know and perhaps might help.

?

You will have to inlighten me as to what the CLIP is, please?

?

Kind regards

?

Colin

?

From: [email protected] [mailto:[email protected]] On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 10:32
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I do not understand the posting about making manual adjustments, I can see that using the suggested approach for fault finding is valid, but not for adjusting the calibration given that the 8920A is software calibrated only. The calibration constants are held in none volatile memory in each module which are read into main ram on power up.

As far as I remember the Cal switch just enables and disables the ability to carry out a calibration via the GPIB port.

Prior to 1999 all 8920A's had a mechanical attenuator, which your appears to have. It then became option 055 with the PIN diode attenuator as option 009.

The only remaining commercial support for the 8920A is provided by Amtronix in the US, who do provide full repair and calibration facilities for them.

Are you aware of the information at Amtronix.com/diagnostic/htm?

Do you have the CLIP for the 8920A, I do if you need it.

Regards

George G6HIG

On Monday, 13 April 2020, 07:25:14 BST, Colin Smithers <colin@...> wrote:

?

?

Hi George,

?

Just measured, the unit is substantially flat (+/-0.2dB) across the range from 1MHz -500MHz, but with the Main input around -2.2dB and Ant input -2.6dB. But these back my point that for a subsidiary function this Spec An is very good indeed.

?

The Main input shows >-25dB return loss, I am yet to measure the Ant input.

?

Looking at the Spec An block diagram two things stick out:-

?

-?????????A signal switch near the front with a Cal setting

-?????????A 4-in-1 DAC which seems to control variable gain amp as well as IF filters

?

So I remain thinking that ?I’m on the hunt for a deeply buried Cal routine. Fiddling with loss internally is clearly possible (from another rreply), but only finding the routine would be future proof.

?

Thanks for info about that HP IEEE 488 program. My Win95 machine does still boot up…??J Gonna have to find an IEEE488 card though. Or info on what the code drives.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 00:37
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I have also seen your posting on the HP8924 group which has additional information in it.

First it is very important to say at what frequencies you are experiencing the errors, the main reason for this is that the front panel on a HP8920A gives the operating range as 400KHz to 1GHz. This is ONLY true for the original electromechanical attenuator version, all the ones that I have seen in the UK have had the PIN diode attenuator fitted which in my experience cannot be trusted below 50MHz. HP claimed 10MHz in their dreams.

Most of these test sets were purchased in the UK for analogue cellular use so the use of a PIN diode attenuator was not an issue.

I would first check to see if the input load measures 50 ohms at the N port, if it does then check and re torque the internal hard line SMA's using a torque spanner, this is very important to avoid damage to the SMA's. There were a number of optimal power handling input loads available, it is not unknown for excess RF power to damage them.

I have not had to work on a 8920A for some years, but as I recall the calibration/adjustment was carried out via the GPIB port using dedicated HP software that would not run on anything later than Windows 95 or possibly 98.

Hope that this helps

George G6HIG

On Sunday, 12 April 2020, 22:18:40 BST, Colin Smithers <colin@...> wrote:

?

?

Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

Hi Colin

CLIP stands for Component Layout Information Package, HP speak for circuit diagrams and board layouts. When you get a service manual for later HP kit it is the text only, the interesting stuff is in the CLIP.

Kind regards

George G6HIG
On Monday, 13 April 2020, 11:28:34 BST, Colin Smithers <colin@...> wrote:


Hi George,

?

Now were motoring! I was unaware of Amtronix, thanks. Clearly they must know and perhaps might help.

?

You will have to inlighten me as to what the CLIP is, please?

?

Kind regards

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 10:32
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I do not understand the posting about making manual adjustments, I can see that using the suggested approach for fault finding is valid, but not for adjusting the calibration given that the 8920A is software calibrated only. The calibration constants are held in none volatile memory in each module which are read into main ram on power up.

As far as I remember the Cal switch just enables and disables the ability to carry out a calibration via the GPIB port.

Prior to 1999 all 8920A's had a mechanical attenuator, which your appears to have. It then became option 055 with the PIN diode attenuator as option 009.

The only remaining commercial support for the 8920A is provided by Amtronix in the US, who do provide full repair and calibration facilities for them.

Are you aware of the information at Amtronix.com/diagnostic/htm?

Do you have the CLIP for the 8920A, I do if you need it.

Regards

George G6HIG

On Monday, 13 April 2020, 07:25:14 BST, Colin Smithers <colin@...> wrote:

?

?

Hi George,

?

Just measured, the unit is substantially flat (+/-0.2dB) across the range from 1MHz -500MHz, but with the Main input around -2.2dB and Ant input -2.6dB. But these back my point that for a subsidiary function this Spec An is very good indeed.

?

The Main input shows >-25dB return loss, I am yet to measure the Ant input.

?

Looking at the Spec An block diagram two things stick out:-

?

-?????????A signal switch near the front with a Cal setting

-?????????A 4-in-1 DAC which seems to control variable gain amp as well as IF filters

?

So I remain thinking that ?I’m on the hunt for a deeply buried Cal routine. Fiddling with loss internally is clearly possible (from another rreply), but only finding the routine would be future proof.

?

Thanks for info about that HP IEEE 488 program. My Win95 machine does still boot up…??J Gonna have to find an IEEE488 card though. Or info on what the code drives.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 00:37
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I have also seen your posting on the HP8924 group which has additional information in it.

First it is very important to say at what frequencies you are experiencing the errors, the main reason for this is that the front panel on a HP8920A gives the operating range as 400KHz to 1GHz. This is ONLY true for the original electromechanical attenuator version, all the ones that I have seen in the UK have had the PIN diode attenuator fitted which in my experience cannot be trusted below 50MHz. HP claimed 10MHz in their dreams.

Most of these test sets were purchased in the UK for analogue cellular use so the use of a PIN diode attenuator was not an issue.

I would first check to see if the input load measures 50 ohms at the N port, if it does then check and re torque the internal hard line SMA's using a torque spanner, this is very important to avoid damage to the SMA's. There were a number of optimal power handling input loads available, it is not unknown for excess RF power to damage them.

I have not had to work on a 8920A for some years, but as I recall the calibration/adjustment was carried out via the GPIB port using dedicated HP software that would not run on anything later than Windows 95 or possibly 98.

Hope that this helps

George G6HIG

On Sunday, 12 April 2020, 22:18:40 BST, Colin Smithers <colin@...> wrote:

?

?

Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

开云体育

Ah! Got it. I shall remember if I should need it.

Rgds

Colin


On 13 Apr 2020, at 13:13, george edmonds via groups.io <G6HIG@...> wrote:

?
Hi Colin

CLIP stands for Component Layout Information Package, HP speak for circuit diagrams and board layouts. When you get a service manual for later HP kit it is the text only, the interesting stuff is in the CLIP.

Kind regards

George G6HIG
On Monday, 13 April 2020, 11:28:34 BST, Colin Smithers <colin@...> wrote:


Hi George,

?

Now were motoring! I was unaware of Amtronix, thanks. Clearly they must know and perhaps might help.

?

You will have to inlighten me as to what the CLIP is, please?

?

Kind regards

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 10:32
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I do not understand the posting about making manual adjustments, I can see that using the suggested approach for fault finding is valid, but not for adjusting the calibration given that the 8920A is software calibrated only. The calibration constants are held in none volatile memory in each module which are read into main ram on power up.

As far as I remember the Cal switch just enables and disables the ability to carry out a calibration via the GPIB port.

Prior to 1999 all 8920A's had a mechanical attenuator, which your appears to have. It then became option 055 with the PIN diode attenuator as option 009.

The only remaining commercial support for the 8920A is provided by Amtronix in the US, who do provide full repair and calibration facilities for them.

Are you aware of the information at Amtronix.com/diagnostic/htm?

Do you have the CLIP for the 8920A, I do if you need it.

Regards

George G6HIG

On Monday, 13 April 2020, 07:25:14 BST, Colin Smithers <colin@...> wrote:

?

?

Hi George,

?

Just measured, the unit is substantially flat (+/-0.2dB) across the range from 1MHz -500MHz, but with the Main input around -2.2dB and Ant input -2.6dB. But these back my point that for a subsidiary function this Spec An is very good indeed.

?

The Main input shows >-25dB return loss, I am yet to measure the Ant input.

?

Looking at the Spec An block diagram two things stick out:-

?

-?????????A signal switch near the front with a Cal setting

-?????????A 4-in-1 DAC which seems to control variable gain amp as well as IF filters

?

So I remain thinking that ?I’m on the hunt for a deeply buried Cal routine. Fiddling with loss internally is clearly possible (from another rreply), but only finding the routine would be future proof.

?

Thanks for info about that HP IEEE 488 program. My Win95 machine does still boot up…??J Gonna have to find an IEEE488 card though. Or info on what the code drives.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 00:37
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi Colin

I have also seen your posting on the HP8924 group which has additional information in it.

First it is very important to say at what frequencies you are experiencing the errors, the main reason for this is that the front panel on a HP8920A gives the operating range as 400KHz to 1GHz. This is ONLY true for the original electromechanical attenuator version, all the ones that I have seen in the UK have had the PIN diode attenuator fitted which in my experience cannot be trusted below 50MHz. HP claimed 10MHz in their dreams.

Most of these test sets were purchased in the UK for analogue cellular use so the use of a PIN diode attenuator was not an issue.

I would first check to see if the input load measures 50 ohms at the N port, if it does then check and re torque the internal hard line SMA's using a torque spanner, this is very important to avoid damage to the SMA's. There were a number of optimal power handling input loads available, it is not unknown for excess RF power to damage them.

I have not had to work on a 8920A for some years, but as I recall the calibration/adjustment was carried out via the GPIB port using dedicated HP software that would not run on anything later than Windows 95 or possibly 98.

Hope that this helps

George G6HIG

On Sunday, 12 April 2020, 22:18:40 BST, Colin Smithers <colin@...> wrote:

?

?

Hi all,

I have an 8920A and the spectrum analyser amplitude level is 3dB out. I have read enough to understand that calibrating this is a bit of a secret. Does anyone know it please?

Similarly for calibrating the power meter.

I have asked the same question on the 8924-series group.

Kind regards

Colin Smithers G4CWH
 

The HP 8920A may be obsolete but it is still supported by Keysight in the UK (and USA)

Worth asking them for a price, it might not be as bad as you think, fully automated calibration is cost effective.
Calibration is no problem, repair is subject to parts availability.
Still lots of these in use. Analog radio isn't dead yet. Demand is strong enough that Keyight sell a 8920A "clone" the M8920A.

Basically a bunch of PXI modules and software. R&S still sell plenty of the CMU500 too.

Robert G8RPI.
 

Good timing, see latest message from Jeff on the HP 8924 Family group. He;s written some code to do it via RS232 :-)

Robert G8RPI.
 

开云体育

And the Marconi 2955,2965 & 2945 series family are all still in strong use.
(Marconi was first to market the radio test set in the form we recognise today)
Regards
Nigel
From: [email protected] <[email protected]> on behalf of Robert G8RPI via groups.io <robert8rpi@...>
Sent: 13 April 2020 21:03:31
To: [email protected] <[email protected]>
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration
?
The HP 8920A may be obsolete but it is still supported by Keysight in the UK (and USA)

Worth asking them for a price, it might not be as bad as you think, fully automated calibration is cost effective.
Calibration is no problem, repair is subject to parts availability.
Still lots of these in use. Analog radio isn't dead yet. Demand is strong enough that Keyight sell a 8920A "clone" the M8920A.

Basically a bunch of PXI modules and software. R&S still sell plenty of the CMU500 too.

Robert G8RPI.

 

开云体育

Thank you Robert and everyone else replying. I am collecting all the suggestions and working out which route to take, or whether its simpler to just keep on entering the offset or just remember the error as I have been doing.

?

But most of all I am filled with simple disbelief that this instrument was left so incomplete in self-cal capability, unless it is just well hidden, in which case why is it so well hidden?

?

The point about it being close so it’s very wide spec is the soft option, as the error is VERY constant, across frequency, time and temperature. I think it could hold +/- 0.5 dB if done properly. The instrument reminds me of the schoolchild that ‘could do better, if only he would only try’. A few decades ago I used a different Spec An that was wonderfully calibrated. Then it went off for cal and on return the horizontal span cal was miles out; signals near the edge of the screen were almost 10% off. I complained and the answer came back from the 3rd party test lab ‘its within spec’. But someone had fiddled as it was not like that previously. However, that is another story.

?

Keep it coming, as its also crystal clear that I am far from not alone with this problem.

?

Kind regards to everyone.

?

Colin

?

From: [email protected] [mailto:[email protected]] On Behalf Of Robert G8RPI via groups.io
Sent: 13 April 2020 22:08
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Good timing, see latest message from Jeff on the HP 8924 Family group. He;s written some code to do it via RS232 :-)

Robert G8RPI.

 

Hi All

Don;t want to distract from the excellent replies, BUT what about this line in the original posting.

"Also trying to calibrate the power meter. I have a calibrated HP438 power meter to guide me"

WHAT ARE THE POWER METER ERRORS?

George G6HIG.
On Monday, 13 April 2020, 22:28:37 BST, Colin Smithers <colin@...> wrote:


Thank you Robert and everyone else replying. I am collecting all the suggestions and working out which route to take, or whether its simpler to just keep on entering the offset or just remember the error as I have been doing.

?

But most of all I am filled with simple disbelief that this instrument was left so incomplete in self-cal capability, unless it is just well hidden, in which case why is it so well hidden?

?

The point about it being close so it’s very wide spec is the soft option, as the error is VERY constant, across frequency, time and temperature. I think it could hold +/- 0.5 dB if done properly. The instrument reminds me of the schoolchild that ‘could do better, if only he would only try’. A few decades ago I used a different Spec An that was wonderfully calibrated. Then it went off for cal and on return the horizontal span cal was miles out; signals near the edge of the screen were almost 10% off. I complained and the answer came back from the 3rd party test lab ‘its within spec’. But someone had fiddled as it was not like that previously. However, that is another story.

?

Keep it coming, as its also crystal clear that I am far from not alone with this problem.

?

Kind regards to everyone.

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of Robert G8RPI via groups.io
Sent: 13 April 2020 22:08
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Good timing, see latest message from Jeff on the HP 8924 Family group. He;s written some code to do it via RS232 :-)

Robert G8RPI.

 

开云体育

Hi George,

?

It is reading around 10% low, compared to the HP438, measured at 1W and 20W, 50MHz.

?

I have not got as far trying to cal this, but again there is no obvious method.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]] On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 23:56
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi All

Don;t want to distract from the excellent replies, BUT what about this line in the original posting.

"Also trying to calibrate the power meter. I have a calibrated HP438 power meter to guide me"

WHAT ARE THE POWER METER ERRORS?

George G6HIG.

On Monday, 13 April 2020, 22:28:37 BST, Colin Smithers <colin@...> wrote:

?

?

Thank you Robert and everyone else replying. I am collecting all the suggestions and working out which route to take, or whether its simpler to just keep on entering the offset or just remember the error as I have been doing.

?

But most of all I am filled with simple disbelief that this instrument was left so incomplete in self-cal capability, unless it is just well hidden, in which case why is it so well hidden?

?

The point about it being close so it’s very wide spec is the soft option, as the error is VERY constant, across frequency, time and temperature. I think it could hold +/- 0.5 dB if done properly. The instrument reminds me of the schoolchild that ‘could do better, if only he would only try’. A few decades ago I used a different Spec An that was wonderfully calibrated. Then it went off for cal and on return the horizontal span cal was miles out; signals near the edge of the screen were almost 10% off. I complained and the answer came back from the 3rd party test lab ‘its within spec’. But someone had fiddled as it was not like that previously. However, that is another story.

?

Keep it coming, as its also crystal clear that I am far from not alone with this problem.

?

Kind regards to everyone.

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of Robert G8RPI via groups.io
Sent: 13 April 2020 22:08
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Good timing, see latest message from Jeff on the HP 8924 Family group. He;s written some code to do it via RS232 :-)

Robert G8RPI.

 

Hi Colin

Are you looking at a common hardware problem that effects the SA and power meter not a calibration issue? Just my thoughts.

My main support role is with Marconi kit where calibration problems usually are frequency dependant.

Good Luck with your 8920A

George G6HIG
On Tuesday, 14 April 2020, 00:31:34 BST, Colin Smithers <colin@...> wrote:


Hi George,

?

It is reading around 10% low, compared to the HP438, measured at 1W and 20W, 50MHz.

?

I have not got as far trying to cal this, but again there is no obvious method.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 23:56
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi All

Don;t want to distract from the excellent replies, BUT what about this line in the original posting.

"Also trying to calibrate the power meter. I have a calibrated HP438 power meter to guide me"

WHAT ARE THE POWER METER ERRORS?

George G6HIG.

On Monday, 13 April 2020, 22:28:37 BST, Colin Smithers <colin@...> wrote:

?

?

Thank you Robert and everyone else replying. I am collecting all the suggestions and working out which route to take, or whether its simpler to just keep on entering the offset or just remember the error as I have been doing.

?

But most of all I am filled with simple disbelief that this instrument was left so incomplete in self-cal capability, unless it is just well hidden, in which case why is it so well hidden?

?

The point about it being close so it’s very wide spec is the soft option, as the error is VERY constant, across frequency, time and temperature. I think it could hold +/- 0.5 dB if done properly. The instrument reminds me of the schoolchild that ‘could do better, if only he would only try’. A few decades ago I used a different Spec An that was wonderfully calibrated. Then it went off for cal and on return the horizontal span cal was miles out; signals near the edge of the screen were almost 10% off. I complained and the answer came back from the 3rd party test lab ‘its within spec’. But someone had fiddled as it was not like that previously. However, that is another story.

?

Keep it coming, as its also crystal clear that I am far from not alone with this problem.

?

Kind regards to everyone.

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of Robert G8RPI via groups.io
Sent: 13 April 2020 22:08
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Good timing, see latest message from Jeff on the HP 8924 Family group. He;s written some code to do it via RS232 :-)

Robert G8RPI.

 

开云体育

Hi George,

I have assumed that all I am fixing are long term calibration drifts as I use this unit at home with its last formal cal a long time ago.

Given the wide formal spec and the third party SA build, I now suspect that cal error could have been in place for literally decades. But again, the performance is very stable which is why it would be great to get it right. Clearly the hardware has the capability for it.

Kind regards

Colin


On 14 Apr 2020, at 01:04, george edmonds via groups.io <G6HIG@...> wrote:

?
Hi Colin

Are you looking at a common hardware problem that effects the SA and power meter not a calibration issue? Just my thoughts.

My main support role is with Marconi kit where calibration problems usually are frequency dependant.

Good Luck with your 8920A

George G6HIG
On Tuesday, 14 April 2020, 00:31:34 BST, Colin Smithers <colin@...> wrote:


Hi George,

?

It is reading around 10% low, compared to the HP438, measured at 1W and 20W, 50MHz.

?

I have not got as far trying to cal this, but again there is no obvious method.

?

Rgds

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of george edmonds via groups.io
Sent: 13 April 2020 23:56
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Hi All

Don;t want to distract from the excellent replies, BUT what about this line in the original posting.

"Also trying to calibrate the power meter. I have a calibrated HP438 power meter to guide me"

WHAT ARE THE POWER METER ERRORS?

George G6HIG.

On Monday, 13 April 2020, 22:28:37 BST, Colin Smithers <colin@...> wrote:

?

?

Thank you Robert and everyone else replying. I am collecting all the suggestions and working out which route to take, or whether its simpler to just keep on entering the offset or just remember the error as I have been doing.

?

But most of all I am filled with simple disbelief that this instrument was left so incomplete in self-cal capability, unless it is just well hidden, in which case why is it so well hidden?

?

The point about it being close so it’s very wide spec is the soft option, as the error is VERY constant, across frequency, time and temperature. I think it could hold +/- 0.5 dB if done properly. The instrument reminds me of the schoolchild that ‘could do better, if only he would only try’. A few decades ago I used a different Spec An that was wonderfully calibrated. Then it went off for cal and on return the horizontal span cal was miles out; signals near the edge of the screen were almost 10% off. I complained and the answer came back from the 3rd party test lab ‘its within spec’. But someone had fiddled as it was not like that previously. However, that is another story.

?

Keep it coming, as its also crystal clear that I am far from not alone with this problem.

?

Kind regards to everyone.

?

Colin

?

From: [email protected] [mailto:[email protected]]On Behalf Of Robert G8RPI via groups.io
Sent: 13 April 2020 22:08
To: [email protected]
Subject: Re: [HP-Agilent-Keysight-equipment] HP 8920A spectrum analyser amplitude calibration

?

Good timing, see latest message from Jeff on the HP 8924 Family group. He;s written some code to do it via RS232 :-)

Robert G8RPI.

 

I second that.
The Marconi 2945 service monitor is some 25 years old but very good.
It has served me well over the years.

Jos PA0AMX
 

开云体育

Temporary fix

?

All,

?

Based on some thoughts delivered by this thread I have found a temporary fix, but it is really only that:

?

-????????? Set SA working

-????????? Inject known power into Ant port

-????????? Set to 1dB/div and establish the error (needs the precision of being on 1dB/div)

-????????? Go to RF Analysis screen

-????????? Inject known power into main port and establish that error

-????????? Go into CONFIG screen

-????????? Set port offsets ‘ON’

-????????? Set those error offsets in the Ant port and Main port windows, to 2 decimal places

-????????? Save these settings to internal non-volatile memory as a pre-set by a useful name. I use ‘CALFIX’

-????????? As the CONFIG screen port offsets do not survive power reset, on first turning the instrument on, recall ‘CALFIX’

?

The instrument is now reading far more accurately on both Ant input dBm and the Power Meter, and these can all be done from the front panel.

?

There remains another offset on SA accuracy from the Main RF port that can’t be removed without also affecting the Power Meter.

?

But as I said, it’s not a particularly desirable or elegant solution, though I hope this is helpful to some

?

Rgds

?

Colin G4CWH/ZF2CA/M3E
 

you should be ble to save the instrument state with the label "POWERON" to restore that atuomatically
 

开云体育

Gem!

Thank you.

Colin


On 14 Apr 2020, at 13:08, jyelmgren via groups.io <jyelmgren@...> wrote:

?you should be ble to save the instrument state with the label "POWERON" to restore that atuomatically

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