Re: HP 8920A spectrum analyser amplitude calibration
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CLIP == Component Level Information Pack == Schematics and Parts Lists (no sorry no Theory of Operation sections) ? David ?
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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
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David C. Partridge