Forums › SA Series Discussions › Can't Lower RBW/VBW with some spans
- This topic has 15 replies, 6 voices, and was last updated 7 years, 4 months ago by Andrew.
- nealmartini August 8, 2015 at 4:06 pm
I am using the Spike software with the SA-44B. I can’t seem to reduce the RBW\VBW setting with certain spans. A simple example is if I have a center frequency of 1 MHz with a span of 1 MHz, I can’t get the RBW\VBW below 6.5 kHz. I want 100 Hz resolution for the spectra and I am willing to wait whatever time it takes for the sweep.
I know I am missing something simple. Help!Andrew August 10, 2015 at 8:33 am
Can you tell me the device information listed in the lower right hand corner of the Spike application? The information I need is the model number, serial number and firmware version. There are two potential model numbers, the SA44 (no ‘B’) and SA44B.
A.J.nealmartini August 10, 2015 at 8:42 am
SA44B 29.88C -4.76V s/n-30300514 Firmware Version 2.10Andrew August 10, 2015 at 9:50 am
Is your start frequency is below 16MHz by chance? There is a limitation on RBW of 6.5kHz if the start frequency of the sweep is below 16MHz.
A.J.nealmartini August 10, 2015 at 10:54 am
Yes the start frequency is 100 Khz (end frequency 2 MHz). That seems like a strange limitation to have to be above 16 MHz for higher resolution?
Is there any workaround? I am trying to use the Signal Hound to show the spectrum of a lower frequency oscillator for a Communications Class I am teaching.
Justin CrooksModeratorJustin Crooks August 12, 2015 at 9:09 am
The best workaround is to show multiple captures. You could do several 200 kHz steps with low RBW. If you wanted you could export them as CSV, paste them together, and then plot using spreadsheet software or your favorite plotting tool.
I realize the RBW/span limitation at low frequencies seems odd, but the combination of hardware limitations at those frequencies, and the sweep performance we wanted for Spike, made it necessary.
JuiceKingParticipantJuiceKing August 13, 2015 at 4:27 am
I just ran into this issue, too. It would be helpful if this limitation were documented in the sales literature and manual.Andrew August 13, 2015 at 9:35 am
See our SA44B hardware manual.
This information is in section 3.1.1 but I realize now there are better places to put this information. I will add this information to the RBW limitations for the future.
A.J.dwc September 29, 2015 at 6:29 pm
That is unfortunate. I have a requirement to scan from 1MHz to 10MHz with 100Hz RBW. That is going to take a very long time in 200KHz increments. Is there really no other way? Is there some way I can automate it?Andrew September 30, 2015 at 9:45 am
This is a hard limitation of the device. Depending on your needs and skills, there might be ways to automate it. The device has a programming interface, if you are good with C programming and it would save you a lot of time, you could programmatically sweep the 1MHz to 10MHz span in 200kHz steps. Or, in the Spike software, you could set the frequency step to 200kHz and use the arrow keys next to the center frequency entry to quickly step through your span.
We apologize for the inconvenience.dwc September 30, 2015 at 12:18 pm
Thanks, the Spike step/arrow sequence helps some. But I might want to consider writing a C program to automate such a series of measurements. Do you have any example code I could use as a starting point? I do see the Labview sample – maybe I can modify that, but C would be better.Andrew September 30, 2015 at 12:28 pm
If you decide to attempt programming the device, we have an API manual here, https://signalhound.com/sigdownloads/SA44B/SA-API-Manual.pdf. There is a code example in the appendix called “Sweep Mode” that shows you how to setup a sweep. This functionality could be performed in a loop to achieve the desired sweep. The labview examples are wrappers around the C functions, so learning the C functions would be beneficial if you decide to automate through Labview. You may contact me at aj at signalhound dot com if you have any programming related questions.
A.J.dwc September 30, 2015 at 12:45 pm
Actually I can’t get the Labview program to run – it is looking for MSVCP110.dll. On the other hand, I do see code samples in the API manual, which should help.Andrew September 30, 2015 at 1:03 pm
The msvcp110.dll file is part of the Visual Studio 2012 redistributable files which can either be downloaded here http://www.microsoft.com/en-us/download/details.aspx?id=30679 or are part of the Visual Studio 2012 install. If you do not use Visual Studio 2012 you will still need to download these to program to the API. We have 32 and 64 bit versions of the API, so you could download both x86 and x64 versions of the redistributable for your PC. We used Visual Studio 2012 to develop the API which is why you are seeing this.
hcglitteParticipanthcglitte November 18, 2015 at 1:30 am
Wouldn’t it be a possible solution if the SW could set the necessary settings to the SA, then perform a 200 kHz sweep, and then just set the new settings for the next 200kHz sweep – but still keeping the display window results for the previous 200kHz sweeps? When the frequency gets beyond 16Mhz just one setting would need to be sent to the device for the rest of the sweep.
This way the hard limitation of the device would be transparent to the user.Andrew November 18, 2015 at 9:55 am
Yes this is possible and something we have talked about implementing, we have just not set aside the time to do it yet.
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