Products > Test Equipment
Agilent E7495 linux root account
TheSteve:
The N1996A supports AM/FM demod though - so you never know if it can be enabled on the E7495.
PA0PBZ:
The option code for the N1996A is AFM so if you have a liberated E7495 just give it a try.
kirill_ka:
--- Quote from: TheSteve on July 12, 2017, 04:07:00 pm ---The N1996A supports AM/FM demod though - so you never know if it can be enabled on the E7495.
--- End quote ---
How do you know that I never know?
toroServer/Dragonfly/Measurements/KernelBasic/Superfly/Am*
toroServer/Dragonfly/Measurements/KernelBasic/Superfly/Fm*
toroServer/Dragonfly/Measurements/KernelBasic/Superfly/am.txt
toroServer/Dragonfly/Measurements/KernelBasic/Superfly/fm.txt
That DSP stuff looks like AM/FM demodulation code for N1996A, doesn't it?
It's not present in egServer. And adding functionality is not just a matter of copying missing files.
technogeeky:
I wanted to bring to attention what I believe is an example of drifting or failing calibration. In a specific sense, none of this matters (because you are probably going to normalize, which makes the measurement you make relative to the problematic measurement below). It's still interesting, and I'd love to hear speculation on why this is happening. I can make further measurements (such as using a different spectrum analyzer to view the output, or a SDR).
The following will tell you the default settings after preset, then show which one or two things to change from the previous. For all tests, the only connection is a 0.5 meter Agilent N-to-N cable.
Two Port Insertion Loss (default settings)
* 375 MHz - 2.5 GHz
* Source Lev Auto (10 dBm)
* Optimize Accy
So when we go to a preset configuration, we have a sudden downward jump at 1 GHz. In addition, the average insertion loss is genuinely lower than it should be. Substituting a different cable has no effect:
If we pick a manual output level, then we can cut down on this effect...
* 375 MHz - 2.5 GHz
* Source Lev Manual (0 dBm)
* Optimize Accy
And if we keep reducing the output level, we can eventually make this jump very small:
* 375 MHz - 2.5 GHz
* Source Lev Manual (-10 dBm)
* Optimize Accy
If we change to "Range" mode, this sharp jump effect totally disappears but the insertion loss offset does not change.
* 375 MHz - 2.5 GHz
* Source Lev Auto (10 dBm)
* Optimize Range
Likewise, if we change to Manual source level and change it to - 10dBm, we get a more or less correct measurement of insertion loss:
* 375 MHz - 2.5 GHz
* Source Lev Manual [/b](-10 dBm)[/b]
* Optimize Range
In case you think this is an effect which shows up only when you have a large span, it's exactly the same up close:
* 999 MHz - 1001 MHz
* Source Lev Auto (10 dBm)
* Optimize Range
* Source Lev
Any thoughts, guesses, or further tests would be appreciated. I have SDRs which I can use to monitor the output from the CW/generator. I can use another spectrum analyzer to view the output. I think I've done this, and I didn't see any sudden jumps at 1GHz exactly. Likewise, when I use another signal generator into this spectrum analyzer (E7495a), I similarly do not see any sudden jump. So this leads me to believe that this effect is from some sort of calibration table that the unit stores for the Two Port Insertion measurement mode specifically.
It's worth noting, too, that the procedure for this originally calls for using a two 10dB attenuators (back to back) on the RF out port. Using an attenuator set does, of course, reduce this effect but it's still noticeable.
ferdinandkeil:
--- Quote from: technogeeky on March 07, 2018, 04:25:01 am ---I wanted to bring to attention what I believe is an example of drifting or failing calibration. In a specific sense, none of this matters (because you are probably going to normalize, which makes the measurement you make relative to the problematic measurement below). It's still interesting, and I'd love to hear speculation on why this is happening. I can make further measurements (such as using a different spectrum analyzer to view the output, or a SDR).
The following will tell you the default settings after preset, then show which one or two things to change from the previous. For all tests, the only connection is a 0.5 meter Agilent N-to-N cable.
...
Any thoughts, guesses, or further tests would be appreciated. I have SDRs which I can use to monitor the output from the CW/generator. I can use another spectrum analyzer to view the output. I think I've done this, and I didn't see any sudden jumps at 1GHz exactly. Likewise, when I use another signal generator into this spectrum analyzer (E7495a), I similarly do not see any sudden jump. So this leads me to believe that this effect is from some sort of calibration table that the unit stores for the Two Port Insertion measurement mode specifically.
It's worth noting, too, that the procedure for this originally calls for using a two 10dB attenuators (back to back) on the RF out port. Using an attenuator set does, of course, reduce this effect but it's still noticeable.
--- End quote ---
I can verify this effect with my E7495B. But this is not erroneous behavior: it is caused by the preamp not spanning the complete frequency range (see https://www.eevblog.com/forum/testgear/agilent-e7495-linux-root-account/msg621126/#msg621126).
When do the test with a short cable (RG316) and a 20dB attenuator, the insertion loss measurement is flat to within 2dB. After normalization I get a nice straight line across the whole frequency range. The insertion-loss measurement is probably designed for longer cable runs with significant loss. This would explain the use of the 20dB attenuation when normalizing. So if your cable is quite short and has negligible attenuation the preamp is saturating, thus giving you wrong results.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version