Products > Test Equipment
Agilent E7495 linux root account
technogeeky:
--- Quote from: ferdinandkeil on March 10, 2018, 11:11:15 am ---
--- 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.
--- End quote ---
Thanks!
I had another problem yesterday which I'm sure is new. The display on the unit keeps turning off the backlight, crazy fast. I can actually sometimes catch it saying in the status bar something like "Turning off backlight in 3 seconds" with a countdown.
Any ideas where this could be stopped or configured?
technogeeky:
--- Quote from: technogeeky on March 10, 2018, 04:52:01 pm ---Thanks!
I had another problem yesterday which I'm sure is new. The display on the unit keeps turning off the backlight, crazy fast. I can actually sometimes catch it saying in the status bar something like "Turning off backlight in 3 seconds" with a countdown.
Any ideas where this could be stopped or configured?
--- End quote ---
This, along with another problem (the network interface not working), just disappeared after I left the unit unplugged for a while (a few hours). So that's good and bad, but more good than bad.
I still had practical problems making two port insertion loss measurements (even with 20dB worth of pads) and Auto (+10dBm) output level. I would get sudden burst of uncertainty in the response right after 1GHz, for almost 500MHz. In any case, I managed to make the measurements by going to 0dB.
ferdinandkeil:
--- Quote from: technogeeky on March 11, 2018, 06:18:42 am ---
--- Quote from: technogeeky on March 10, 2018, 04:52:01 pm ---Thanks!
I had another problem yesterday which I'm sure is new. The display on the unit keeps turning off the backlight, crazy fast. I can actually sometimes catch it saying in the status bar something like "Turning off backlight in 3 seconds" with a countdown.
Any ideas where this could be stopped or configured?
--- End quote ---
This, along with another problem (the network interface not working), just disappeared after I left the unit unplugged for a while (a few hours). So that's good and bad, but more good than bad.
I still had practical problems making two port insertion loss measurements (even with 20dB worth of pads) and Auto (+10dBm) output level. I would get sudden burst of uncertainty in the response right after 1GHz, for almost 500MHz. In any case, I managed to make the measurements by going to 0dB.
--- End quote ---
Glad to hear that the problem went away on its own.
Regarding the insertion loss measurement, 10dBm just might be a little much for the preamp. Did you normalize (aka calibrate) the measurement?
technogeeky:
--- Quote from: ferdinandkeil on March 11, 2018, 11:24:06 pm ---
--- Quote from: technogeeky on March 11, 2018, 06:18:42 am ---
--- Quote from: technogeeky on March 10, 2018, 04:52:01 pm ---Thanks!
I had another problem yesterday which I'm sure is new. The display on the unit keeps turning off the backlight, crazy fast. I can actually sometimes catch it saying in the status bar something like "Turning off backlight in 3 seconds" with a countdown.
Any ideas where this could be stopped or configured?
--- End quote ---
This, along with another problem (the network interface not working), just disappeared after I left the unit unplugged for a while (a few hours). So that's good and bad, but more good than bad.
I still had practical problems making two port insertion loss measurements (even with 20dB worth of pads) and Auto (+10dBm) output level. I would get sudden burst of uncertainty in the response right after 1GHz, for almost 500MHz. In any case, I managed to make the measurements by going to 0dB.
--- End quote ---
Glad to hear that the problem went away on its own.
Regarding the insertion loss measurement, 10dBm just might be a little much for the preamp. Did you normalize (aka calibrate) the measurement?
--- End quote ---
Yep. I don't believe the 10dBm claim, but that's what it says on the source level of my instrument. I'll take some SDR screenshots (while restraining the tracking generator to a small frequency range). It normalizes fine. But once I make a measurement, and it's still in +10dBm mode, there is a bunch of noise right after 1000 MHz.
JessieAMorris:
Just picked up a working unit off the 'Bay for $300 shipped. Excited to start playing with some RF goodness.
Navigation
[0] Message Index
[#] Next page
[*] Previous page
Go to full version