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I started using SA44B together with TG44A and SW 2.18B for measurements of power distribution network characteristics of PCBs – levels below -80dBm in range from 10kHz to 2GHz. That means very wide sweeps with small RBW => 1 sweep per 30 minutes.
I am experiencing strange issues with settings of level. I attached series of pictures to demonstrate the problem. Starting point is ATTEN set to 10dB. TG is set to -10dBm, so curve is on -10dBm what is correct. When I set ATTEN to 0dB, I expect the curve would be 10dB higher but it goes to -20dBm. Is my expectation wrong? But when I set ATTEN back to 10dB the curve goes to 0dBm instead of -10dBm where it was before. That is I suppose wrong. When I set e.g. dB/div to different value and than back to the previous, the curve will get to -10dBm. The same will happen when I change TG amplitude level and then I put is back, it will get the curve to -10dBm.
To the software. I do not understand what is happening when i set start and stop frequency. Those numbers are somehow automatically changed when TG is enabled, e.g. when i set 1MHz as start (just to have some measurements so low) and 2GHz stop, I end up with something like 3MHz to 1.995GHz. I must use 100kHz to 2.1GHz to get 1.2MHz to 2.09 GHz.
There is very low control over sweeps which takes long time. It is not easy to recognize SW is already working (no activity indicator), sweep time is displayed when sweep is finished, so I must wait and I don’t know when the measurement will be finished. I would wish current sweep would be interrupted once I set new parameters, but it will finish the sweep and then it start new one with new settings. It means I would need to wait e.g. 20 minutes to apply new settings. It is easier to exit software and start it again.
When I use STOP button for TG, SW will freeze for 10 seconds and when I use START again it usually stop working and SW must be terminated. Change of REF level, ATTEN, dB/div parameters cause changes of TG steps so I need to set everything again.
ATTEN value and other settings are not present in exported CSV file so it is not easy to track measurements from exports.I am very missing logarithmic sweep of frequencies.
Is there any chance there will be fixes introduced in some new version of SW? I consider the HW very well for the price but the control software is very limited. Is there any plan to use the same software as for BB60 to SA44? Even as cost option?
Petr
The current TG software is really touchy. It sounds like you are trying to make sensitive measurements. Before you enter TG mode, try setting your reference level to -30 dBm, then attenuator to 0 dB. Then enter TG mode, set reference level to 0 dB, store thru. This should keep the 0 dB attenuator setting and give you a flat response.
The new software will be so much better for this.
Agreed the current TG application does some odd things.
Personally I find that I must set and confirm all parameters are correct before pressing TG START. If I change any of the parameters while running, the result is not what I would expect. If a parameter needs changing, one must STOP first, change the parameter, and then START again.
I believe sweep issues and ability to interact with the user interface while sweeping is going to be part of the new upcoming software release, so looking forward to trying when it is available!
Also agreed on the accuracy – it SA/TG44 agrees well with the much more expensive R&S ZVL I have access to, given the huge disparity in price point.
Just curiosity on my part – what are the small steps in measued level at certain frequencies? I guess it’s something in the SA44b hardware, as it has always done this. See attachment. In this case, the freqs are about 80, 140 and 250 MHz.
Andy,
These might be from steps in input / output impedance at those frequencies. You can remedy this by adding a 3 dB pad to the output of the TG and input of SA before “store thru” and keep them on for all measurements. This improves return loss by 6 dB and cleans up impedance mismatch-related measurement error.
Another thing you can do is “store thru” with a similar length cable to the circuit you will be testing.
If these steps occur with 30-50 dB insertion loss, you may need to “store 20 dB pad” to get rid of them.Thanks Justin.
Another question (sorry!). Over on another site, were were comparing TG crosstalk levels on another well-known analyser (Rigol). Once we’d done that, I thought I’d see what result the SH returned (should be very low level). I set up a sweep from DC to 1.5 GHz and noted the baseline noise level, but just by chance I then raised the start freq to 300 KHz and the niose level dropped by several dB. Is this anything to do with the auto-settings reducing the DC spike? Or is something odd going on?Andy,
250 kHz is the magic number. Sweeps that start below this cannot use the preamplifier, which raises the noise floor.The TG sweeps now use two sweeps to build the final result. One covers the low loss region (approx. 0 to -40 dB for a passive device, or -20 to 20 for an active device). The other covers the high loss region (approx. -40 to -80 dB or -20 to -60 dB for an active device).
When the start frequency is below 250 kHz, the software selects the active device range since it cannot use the preamplifier.
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