CIKBlog

Rigol DSA815 Spectrum Analyzer...

This is a place holder for my soon to be deilvered Rigol DSA815-TG spectrum analyzer...

• 9 kHz to 1.5 GHz Frequency Range
• Typical -135 dBm Displayed Average Noise Level (DANL)
• -80 dBc/Hz @10 kHz offset Phase Noise
• Total Amplitude Uncertainty <1.5 dB
• 100 Hz Minimum Resolution Bandwidth (RBW)
• EMI Filter & Quasi-Peak Detector Kit (optional)
• VSWR Measurement Kit (optional)
• Standard with Preamplifier and AM/FM Demodulation Function
• Plenty of measurement functions (optional)
• 1.5 GHz Tracking Generator (optional)
• 8 inch (800×480 pixels) high-definition display with clear, vivid,
and easy to use graphical interface
• Complete connectivity with standard interfaces such as LAN,
USB Host, USB Device and GPIB (optional)
• Compact size,light weight (9.4 lbs)

Lecroy 9450 FFT Configuration Tool...

Having used a Lecroy 9450A oscilloscope for several years I have yet to find a better all round general purpose digital 'scope in it's price range. $400 to $600 on eBay.

When equipped with the WP02 waveform processing option it can also function as a very competent spectrum analyzer with frequency resolutions ranging from 20μHz to 100MHz, and spans of 0.5mHz to 5GHz, these in a series of possible combinations based upon the timebase setting and selected number of sample points to be processed.

Here's a photo of my 9450A displaying the FM radio band spectrum as available here in Saint Augustine FL:

To gather this spectrum I wanted a 50kHz frequency resolution, and a 200MHz span.

Selecting the FFT frequency resolution is somewhat easy as it is the reciprocal of the timebase setting times 10:

Rearranging this to calculate the timebase setting from the desired resolution we get:

Not too bad...

However calculating the span requires that you know the sampling rate (a factor of timebase setting and RIS¹ or SS² mode), and the maximum number of sample points captured and number of points to be used in the FFT calculations:

where:

While both span and resolution are displayed on the FFT setup screen, configuring the timebase and number of points to get the resolution and span you seek can be a lengthy trial and error process. I wrote the LecroyFFT.exe application presented here to eliminate the need to use the formulae presented above and/or the trial and error process.

It looks like this, here showing the needed time/division and points for the 50kHz resolution and 200MHz span used to capture the FM Band spectrum shown above:

You will also see that the capture characteristics for the needed timebase setting are displayed at the bottom of the dialog. Shown are the seconds/division, the RIS samples/second and record length, and the SS samples/second and record length.

To use the application just select the desired resolution from the list at the left, this will cause the needed timebase setting to be displayed (2μs above) and load the span list with the spans available for that timebase setting.

Next select the desired span (and RIS mode if desired and available--more about this below), the required number of points to be used in the FFT calculation will be displayed (8000 above).

That's it, now just set the indicated time/division on the 'scope, and set the required number of calculation points in the FFT configuration menu.

RIS mode is required for timebase settings of 1ns to 5ns, available for settings of 10ns to 5μs, and not available from 10μs to 5000s. The application will show messages indicating the availability of RIS mode.

There is only one application configuration option, so to keep things simple I just included it of the About dialog:

Checking the Confirm Exit box will cause the application to pop-up a dialog when you close it (via the standard Windows Close button). The dialog will ask if you wish to close or minimise the application, I added this because I found myself closing the app when all I wanted to do was minimise it. Some find this sort of thing annoying so I made it configurable.

You can download the application in a Windows installation package by clicking here.

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¹ - RIS = Random Interleaved Sampling capture mode
² - SS = Single Shot capture mode

Sony Alpha +30 series batteries...

I recently purchased a Sony Alpha α230 digital SLR, got it on sale at Walmart for $300! I had done some research on DSLRs and when I found that the Sony Alpha series used the same lens mount as the Minolta Maxxum film cameras my interest in Sony's offerings was pretty much cemented in place as I had a number of those lenses in the closet.

One item I did look to purchased however was a spare battery. They are $60 retail, $55 at WallyWorld, but piece of cake says I, log on to eBay and find a reasonably priced after market unit that would ship from the US. I bought one for $20 with free shipping, here's where the problems started...

It turns out that the Alpha +30 models (the α230/330/380 series) have a Battery Detector module that communicates with the battery via a one-wire serial protocol--this is claimed to be used to monitor state of charge, internal temperature and other parameters.

Here are the schematics from the service manual showing this connection and the Battery Detector module:

 

If the battery does not support this communication the camera will display "Incompatible Battery. Use correct model." and shut down. The first time you insert an incompatible battery the camera will appear to power-up correctly, but then display the error message and shut down when you attempt to take a photo or change a setting. Subsequent power-ups (with removing/reinserting the battery) will go directly to the error message and shutdown.

I am not aware of any after market batteries that support this communication, so ask questions before you buy and be prepared to have vague and "it should" sort of responses when you ask "Will this battery work with a Sony Alpha α230/330/380 camera?".

Startup...

I have been meaning to do this for some time, if nothing else it will let me record stuff I want to keep track of...