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Andrew,
Unless I am doing something wrong, this is not working for me. I set the Reference Level Offset in Settings, save it as part of my preset 2, close Spike, load preset 2, Reference Level Offset is back to 0.00db. Can you clarify.
THanks.
That’s a shame. I had used this in the past to measure the delay between my logic TX enable signal and the actual RF envelope, which is crucial in pulsed RF systems. I guess I’m very surprised that this important feature has been removed.
I agree that you should grey out the controls in Spike and save lots of people lots of frustration trying to get it to work.
FYI, the spec section of the manual still refers to this capability.
Well, I was finally able to delete the erroneous screen captures, but now I cannot edit my post….:(
Below are the corrected captures with spur reject off and min/max detector setting.
Justin,
Yes, there is a 20db pad on the input to the SH (0dbm into SH), and it was not changed between the Spike and V2.18d app measurements. I am using peak hold for measurements since that’s what the FCC lab does.
Justin, Andrew,
This is still a problem. In fact, I can now reproduce it on two different SH units (SA124A & SA44B). Perhaps it could be the that the amplitude or the modulation format of the measured signal is affecting the measurement algorithm? My radio puts out +20dbm with a OQPSK signal. Your measurements above were made at -40dbm, not sure of the modulation. There shouldn’t be a difference, but there is. As stated earlier, I have verified my measurement with a Rhode & Schwartz spectrum analyzer at my FCC test lab. How do you propose we address this?
AJ
Can you try attenuating the input to ensure you are not in compression?
There is a 20db fixed attenuator on the input of the SH and the Ref Offset is set to 20db.
With your ref offset active, set the reference level to +40 to see if this affects the measurement. I am concerned that the signal is possible being compressed in the Spike software.
I have changed the Ref Level from +40 to 20dbm with very little difference in peak power measured.
If you have a generator, can you try a similar test?
I don’t have a generator other than the radio being tested. It’s output is +20dbm.
A.J.
For the Spike software, to get comparable measurements, ensure video units are set to power, detector is set to average, and disable spur reject in the settings file menu. With these settings, you should see similar readings.
Attached is a snapshot with the settings you suggested. Note that the measurement result is very nearly the same as before. This is a serious issue. Any other thoughts?
For a wide band signal like this, ultimately, you will want to compare channel power readout.
I am trying to make a PSD measurement for FCC part 15 compliance which requires that you measure the peak power in a 3khz RBW. How does the channel power readout help?
Here’s a better representation of the channel markers. I am using the Channel Power markers to illustrate.
I’m starting to think that “mask” may not be the correct term for what I am looking for. Perhaps it should be called “channel markers”. What I would like to see is a semitransparent vertical bar, similar to the one shown in the attached file, centered on each “channel” that I specify in a file similar to the limit-line and path-loss file format. For each channels I specify, a vertical bar is plotted whose width is determined by the settings in the imported file. A small gap (or line) between the channels will help show their boundaries. Perhaps an optional label could be included that is plotted at the top of the channel marker.
For example:
906 (channel center), 2 (channel width), “CH 1” (label) <cr><lf>
908, 2, “CH 2” <cr><lf>
910, 2, “Ch 3” <cr><lf>
etc.Well, it sort of works, as long as all of my signals are below -40dbm. I guess it’s a poor-man’s mask.
Any chance of a real custom mask utility? In your spare time?
Thanks,
Mike
AJ,
Yes, that is what I am looking for. But the plot that shows up does not look like what I would expect.
