Hi,
I need some help determining the cause of a VSWR spike on 1 meter cable assembly. This happens only when the number of points is 801 as opposed to 401 points. I have attached the two plots for your reference.
Thanks in advance.
AJ
Edited by: AJ3 on Feb 16, 2015 8:46 AM
Edited by: AJ3 on Feb 17, 2015 9:03 AM
I need some help determining the cause of a VSWR spike on 1 meter cable assembly. This happens only when the number of points is 801 as opposed to 401 points. I have attached the two plots for your reference.
Thanks in advance.
AJ
Edited by: AJ3 on Feb 16, 2015 8:46 AM
Edited by: AJ3 on Feb 17, 2015 9:03 AM
1. Did you perform your Open,Short,Load cal (or ECal) using the same number of points as when you made your measurement? If not, then you are using interpolation, which can cause problems, especially on wide sweeps such as this. This is the cause of the smaller spiky-ness on most of the trace.
2. Do you have Step Sweep enabled? By default, step sweep is NOT enabled and we do not guarantee +anything+ unless it is enabled. Note: Using an IFBW of 1KHz or less will automatically use step sweep even if it is not already enabled.
3. The large spike could be due to a band cross. The effect of this will be made worse by not following items 1 and 2 above. I am at home now and do not know if that is a band cross or not. There is a program in the service directory called ShowBandInfo that will list all the band crossings.
To avoid this issue, perform your user calibration at a high number of points such as 1601, 3201, or more; especially with this wide of a frequency sweep. Perform your cal with an IFBW of 1KHz or less. If this is too slow for you, then at least turn on Stepped Sweep! Once your cal is done, you can then take your measurements at a sub-multiple of the number of points that you used for the cal. For example, if you made your cal at 3201 points, you can take your measurement at 1601, 801, 401, 201, etc. number of points.
Try this and let us know the results. There are other solutions also, but the above is the easiest.