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I think it would sometimes also be very interesting to have an information what attenuator is switched in when the unit is set to auto atten. Especially in noise figure measurement.
HP 346 B is a good but still expensive noise source.
Works well with SM200B. As most noise sources this one needs a 28V DC powersupply. You have to attach an external power supply.
the best ?
SM200B and a ( any ) noise source is a very good way to get an overview for noise figure measurements. Be carefull with cheap noise sources from the internet. Most of them have plenty of power and may damage your analyser.
I have also used one of the 20 EUR noise sources from the internet. All power stages have to be removed. Then it can be calibrated against a known noise source ( HP346B and Eaton 2075 noise gain analyser ). Works well up to 2GHz with comparable results to HP346B. Still frequency range of HP346B is far beyond the home brew one.
Keep in mind : noise figure measurements are not as trivial as it looks.
this is working fine.
in the release notes from 3.8.0 you wrote:
> SCPI command FETCH:ZS? can now return average power.
I have tried but could not get the expected result.
Parameter 1 delivers IQ Values that can be used with this formular: 10*log10(mean(I^2 + Q^2))
Parameter 2 delivers the number of IQ values
looks like no other paramters are implemented.
Can you please explain how FETCH:ZS? retrieves the avg power value in zero span mode.
thanks for your explanation of the calculation the amplitude value from the I/Q data. Still it would be nice to fetch the value from the analyser. The workaround generates lots of data, especially if you need many amplitude values…
Yes, I would be interested to have a SCPI command to retrieve it. It makes the resulting script much more easy.
of course a standart noise source needs 28V. There is no need to drive it direct. It would be rather easy to use a trigger signal to drive some switching logic. Just need a signal and maybe a delay to start the next measurement.
It would be a nice feature if you would take the attenuator (if mounted) into account.
Since this is not really important for NF it would give the right values in the gain plot for documentation purpose. I was thinking about using the “reference level offset” but I think it is not the best solution. Maybe a field “loss after dut” will be better
Thanks for the improvement in 3.5.13.
Shame on me, I had a wrong manual.
Compliments to you for intuitive implementing of this feature. I will check again with “4.12.5 Limitations” in mind
I spent a little more time then I wanted. The function is working nicely and is producing results that are close to what the Eaton is measuring. I have seen peeks in NF at about 850MHz, but this is only with one DUT and I have no idea why…
Exporting the complete hot/cold data could probably be also a nice feature.
An application note of how the measurement is done could also be very helpfull. Especially what is done with the input attenuator and the preamp. That also leads to the question what NF the BB60C has. I have not found any informations about this.
One more automation step could be evaluating the optimal RefLevel, but the first one is definately temporary storing the noise source
cal to skip steps 1 and 2 of the four steps when you want to repeat the measurement
Thanks for this feature.
thanks for the information about the SA44/124.
I played around with the new NF function and compared this with the values I get from an Eaton 2075. I have a HP 346B and a selfmade noise source that are reproducing realistic values. In the frequency range of about 800 to 1000 MHz I am always getting values to high. The rest is really close to what is expected. I will invest some more time next week and have a closer look.
For my last question:
There was a interesting article here
I have not tried this, but the steps to use this measurement method are very close to yours.
nothing to apologize for. Thanks for this great product and your great support.
just found out that the position of the limit lines depend on the RBW. By increasing the RBW the limit lines are shifting left.
just found the time to come back to the problem. It is much better in 3.5.11 but still not correct. Limitlines are slightly to low in frequency, but this is working.
Limitlines should be right on grid.
thanks for the response. I still have an older version of spike and I can wait for the fixed one.
I think there is no need to automatically calc IP3 or IP2. But for documentation it would be very nice to have a display field with a title where you can do marker math and place some comments
that is good to hear. Sweeptime is normally not what you need while using a TG with 201 points. Adapted frequency rage would be nice. Why not using the VSGs as TG. That would be a nice bundle even if the actual VSG is not covering the full frequency range.
limit testing in version 3.1.14 is now nearly working as expected. Thank you for great service.
Still there is something strange. In the picture you will see the two lower limit lines ( red needles ) that will check for minimum power level of two carriers. They should come up to +22 dBm. Instead they just show somthing about +18 dBm.
It is working when you fall below the graphical line, but the line is not corresponding the values in the Limit Line Table.
Limit2.jpg should not show pass !
I think you are right about the RBW. If I come down to a RBW of about 300 Hz it is working. Since this was for testing and quick checking of IP3 of an amplifier, I increased RBW to 5kHz. In this case I can see the two main carriers. With the low RBW they hide behind the limitlines ( picture lowrbw.jpg ).
If I increase the RBW to 3kHz it will pass ( picture rbw3khz.jpg ).
It will fail at a summ level somewhere below -73 dBm.
It gets worse if you increase the span…
Anyhow this was working in Version 3.1.11.
So the algorithm of checking has changed. If it is like your wrote that you are checking single samples against the limit you may run into trouble when you have a good generator. Should you not check against a interpolated line between two samples ?
I really hope you can get it running, because I ever wanted the limit lines stored with the preset as it is first done in this version.
The limits I used:
thanks for your immediate support. I thought that this is working like you explained, but I still cannot get it running.
I would like to switch to a more simple to replay example:
– Single carrier 250 MHz
I used limit line 3.
Setting to Lower Bound will always pass.
Setting to Upper Bound will always fail.
No matter what the aplitude is. Increasing RBW does also not solve the problem.
Two more problems that I would put on the bug list:
– it is not possible to enter these values in the application, since rounding of the frequency will happen. It has to be done in a text editor and you have to load it. Still you cannot view it because of roundings…
– Changes to the limit lines will not always reflect to the app. Sometimes you will have to switch on and off or switch to another line. I have not found any system behind this behavior.