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Post by greenwmg3ype on Jul 7, 2014 10:08:32 GMT -5
I seem to be having a problem with the the upgrade version 876 displaying the correct value of return loss. The impedance value are reported correctly. A plot of a trap dipole when taken in prog version 865A reports a return loss of 23.8 db, but in version 876 this is displayed as 3.12 db. The graph lines show the minimum to be in the correct place and the graph scale appears correct,its just the readout on the numbers display. Thanks Mike  |
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Post by Bob on Jul 7, 2014 15:17:55 GMT -5
Hi Mike,
This is a very good technique for documenting a problem.
The graph looks ok but the values for SWR and Return loss on the right side of the graph are incorrect. Based on the valus for Rs and Xs, the SWR should be about 1.12.
It's not obvious why the numbers are so far off. I'll look into this.
73/Bob
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Post by greenwmg3ype on Jul 7, 2014 17:23:45 GMT -5
Thanks Bob, Looking further into this, I thought that some of the problem may have been the cal file. I ran a custom cal, but the program locked up with i/o error very early on in the short cct measurement. The program was closed but the aim remained locked up with the red run light on. The only way to clear the AIM 4170 was to switch off the psu. I decided to make sure my FDI usb drivers were up to date and updated the driver. The updated driver changed things slightly, with a message saying cal aborted due to ref missing. Another try gives the message " No data from I/O port numchar=71 numpts=16. On retry back to message There is no ref signal from the aim cal aborted. I wonder if some of my problem lies with the usb interfacing. Updated driver all works ok in prog vers 865A. Regards Mike  |
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Post by greenwmg3ype on Jul 7, 2014 18:17:00 GMT -5
Bob, More data. I ignored the error messages and selected custom cal. Although the aim was showing I/O error messages the program prompted me to connect the short cct, it wasn't happy with the short which the instrument claimed was around 2 ohms, the prog allowed me to continue. I could see behind the red error messages that data was being processed very slowly. After a long time 10 mins maybe, the program asked for O/C, again it was reported that the the load was not infinity but allowed me to continue. This run went much quicker and I was prompted for the load (I used 200 ohms), this again was processed very quickly and the program allowed me to save the file. Once this cal file was in use, the program reported correct parameter values. See attached graph. Thanks again for looking into my problem. Regards Mike  |
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