Yes, I recommend the two things.

The limiter does not come with an additional attenuator, that would be separate.

I didn’t think to ask, what frequency are you operating at? Our limiter only goes down to 30MHz, so if you are lower frequency than that and you wanted a limiter, you would need to find a different part.

Right now you have 20dB of attenuation. I recommend 30dB of attenuation and an RF limiter.

The RF limiter will protect the front end of the SA, the 30dB of attenuation is necessary to bring your 40dBm signal down to 10dBm where the SA is no longer in compression and can accurately measure the input. Our RF performance specifications only hold to +10.

Regards,

Hi Dave,

Your conversions look good.

That said, I would not operate your 10W transmitter with the 20dB pad into the SA44B. +20dBm is a hard limit. I would add another 10-20dB of attenuation as well. I would try to stay below +10 dBm, the SA44B goes into 1dB compression at about 16dBm for some frequencies.

We also sell an RF limiter you might be interested in, the VLM-63-2W-S+. If you knock the input down to +10 and then add this +12dBm limiter to the front end, I think you would be safe from costly front end RF damage.

Regards,
Andrew

You’re welcome Miran, thanks for the suggestion.

Regards,
Andrew

Hi Clark,

I’m not familiar with any sort of conversion, but the common way to measure power of a modulated/non-CW signal is to use the channel power measurement. You can enable/configure that in the measurements control panel. When using the SA44B, for the most accurate channel power measurements, disable spur rejection in the File->Settings menu.

Let us know if you have additional questions.

Regards,
Andrew

Hello Sri,

Our device APIs are standard Windows DLLs. The interface is exposed through a set of C functions, which means you can call these functions from most programming languages like Python, C++, Matlab, etc. Each language will have its own development environment. If you were programming in C++, I would use Visual Studio, which you can download and use for free (for small business/non commercial projects). We do not have any guides for using VS or for setting up your development environment.

Regards,
Andrew

Steve,

The I/Q data is scaled to mW. To calculate the power of any given I/Q value in dBm, use the formula
dBm = 10*log10(I*I + Q*Q)

Let me know if you have follow up questions.
Regards,
Andrew

Hello bittware,

You will want to use the :CALC:MARK:MAX and :CALC:MARK:X?; Y? commands to move the marker to the peak and read the position.

You will find examples of usage in the SDK and descriptions of these commands in the SCPI manual which is also in the SDK.

https://signalhound.com/download/bbsa-application-programming-interface-for-windows-3264-bit/

Regards,
Andrew

Hello Guptaanand05,

The Spike software does not support the export of snp/touchstone files. You would need to export as CSV and convert then.

Let me know if you have additional questions.

Regards,
Andrew

Andrew,

I fixed this now, and it will be in the next release of Spike. Thanks for the heads up. Until then you might have to use the print screen feature or snipping tool utility in windows. Sorry about the inconvenience.

Regards,
Andrew

Hi Dan,

Thanks for the feedback and bug report. Don’t worry about reposting it in another forum.

Can you email me with more information about your setup. Initially I have been unable to reproduce the issue. Email me at “aj at signalhound dot com”. If you can send me a picture of the setup of the application at the time of the capture (including the settings control panel and the recording control panel), and any other information that would help me attempt to reproduce the issue. I think you are correct that it is an issue with Spike, it might be tied to a specific configuration.

Regards,
Andrew

Thanks for the request Andrew.

Hi Andrew,

I’ll look into this, see if there is a way to get a fix into the next release. It looks like a bug maybe introduced when we updated the spectrogram plot? I’ll let you know what I find.

Thanks for the heads up.

Regards,
Andrew

What does the CPU usage look like when real-time is running? Is there an increase/jump in cpu usage when you move your mouse across the screen?

Are you running your monitors off the integrated GPU or do you have a dedicated GPU?

If you have time and the ability, I would be interested if it helps to run just a single monitor setup with a ~1080p resolution. I’m ultimately curious if it is related to your specific video setup. I can’t reproduce any issues here on a i7-6700 running 2 1080p displays.

Do you have any anti-virus software running other than windows defender? If you have any other heavyweight software running it might be interesting to see if closing it out helps any. This might be a long shot, but setting the PC to the high performance power plan might help, go to the “power options” menu in the control panel and set your power plan to “high performance”.

Regards,

Will you try something for me? It looks like you have a high resolution monitor? Maybe a 3K/4K monitor? Does it help if you try this same test after changing your PC resolution to 1080p? (or any resolution below 1080p)

Regards

c3dr,

What kind of PC are you running the unit on? I’ve seen this type of behavior before on a low power laptop. Usually indicative of the PC not able to keep up with the processing and creating erroneous results like this. For the real-time spectrum analyzer modes we recommend quad core i5/i7 processors to keep up with the processing requirements.

I look forward to your response.

Regards,
Andrew

Hi Steve,

Yes, the center frequency you select in the bbConfigureCenterSpan is the 0Hz/baseband frequency of the IQ samples and your IF bandwidth (27MHz) is centered around this frequency.

Regards,
Andrew

Hi stevecrm,

So you may indeed be pulling the I/Q data and plotting it correctly, but unfortunately it will still not produce the constellation plot you see in Spike. The reason for this is that Spike is doing additional processing between acquiring I/Q data from the API and plotting it in the constellation plot.

The main steps the Spike software is performing is resampling, symbol timing recovery, carrier recovery, and filtering. This can be quite a complex subject and not one I can cover in a forum post. You can find more information in a digital communications textbook, by searching online for search terms like “PSK demodulation”, or exploring software packages like GNURadio which has software blocks for the major components of a PSK receiver.

Keysight has an excellent block diagram of the various components in a spectrum analyzer when making PSK modulation measurements. See the following link on page 282.

http://literature.cdn.keysight.com/litweb/pdf/E4440-90620.pdf

I hope this helps, let me know if you have follow up questions.
Regards

Noeldi,

Good question, and it’s a bit tricky to answer. Our waterfall plot currently is only available in the sweep mode. Each sweep is plotted on the waterfall and generally each sweep is going to take 1ms+ depending on the analyzer and settings. So that would be your minimum resolution.

To get 10us resolution in a waterfall plot, we would need to introduce the waterfall plot into the zero-span mode (or some other I/Q mode) and perform overlapping FFT’s on the IQ data. We don’t have anything like this in Spike right now.

As Justin mentioned, our max bandwidth IQ device is 40MHz right now with the SM200A, or 27 MHz with the BB60C. Both are programmable and this type of resolution is possible if you were willing to program and work with the I/Q data yourself using our API.

We are working to increase the I/Q bandwidth of the SM200A to 160MHz for up to 1 second captures. This is still in development.

Regards,
Andrew

You can change the max file size allowed in the preference menu. It is limited to 1GB when running the 32-bit version of Spike.

There are several ways you could reduce file size depending on your needs, you can increase RBW, add a sweep interval, or take advantage of the decimation in time/freq on the recording toolbar.

If you need even more flexibility than what Spike provides, you could consider programming to the API directly, then you full control over the acquisition and recording process.

Regards

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