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Tuesday, 30 August 2016

New version of SMA Simple Spectrum Analyzer!

Here is the change log, it has been a productive night:

  • Corrected dBm calibration for improved precision
  • Implemented new function: Powermeter - not sure if it is correctly implemented
  • Implemented new graphics engine
  • Spectrum/Waterfall in main image can be saved as PNG
  • Introduced change log
  • Cleaned up GUI (Setup screen)
  • Cleaned up some code
  • Added a SET button on Sweep Generator (less prone to crash due to open RS232 port)
The picture shows ASTRA 19.2E, using the MIN/MAX and LIVE traces.
Refresh rate with 500 samples (quite a high resolution compared to common field meeter) is about 0.333 fps.
This picture shows the waterfall diagram of frequency range 144MHz-180Mhz

It uses the same activation code, in case you already have one. If not, just follow the instructions on first run.

Please give me feedback:
  • Does it work?
  • What do you use it for?
  • Suggestions for enhancements
Have fun!


Saturday, 27 August 2016

Where to get the SMA Spectrum Analyzer software


Because most e-mail servers will reject messages with an attachment containing an executable, it is difficult to send out the software by e-mail.

Even zipped and with a *.txt file extention inside another zip, files get rejected!

Since doesn't provide any file hosting, I have been using the fabulous forum to upload my software.

Please get it from here (requires registration): 

or from here:

Make sure you use the last attachment and while you're at it, take a glance at the posts of this thread, as many questions might be responded.

You still need to request an activation code by e-mail. Just send me the system code displayed by the software: it will be automatically copied to the clipboard, so no need to retype it!


Sunday, 21 August 2016

Reflectometer Measurements - Part 2

I have tried to measure three cables and this is the result:

Interesting notes:

  1. The longer the cable, the smaller the interferences. This requires to set a smaller span in the spectrum analyzer. Unfortunatly at 100m cable length we reach the limit of the SMA Spectrum Analyzer's resultion.
  2. To overcome this limitation (and because my test cable is exactly 100m long - for obvious reasons), I put my Spectrum Analyzer Software into AVERAGE mode. This will produce a more distinguish spectrum, making the measurement easier.
  3. I traced the obtained data (frequency span vs cable length) in Excel and unfortunatly, the curve is not linear at all. This may be due to several factors:
    1. Reduced precision of the SMA Spectrum Analyzer
    2. Reduced flatness of the low cost SMA noise source
    3. Unsuitable and unbalanced connectors (see my previous post: in the picture you see the chain of connectors converting between SMA, BNC and F-type - some 50 Ohm, other 75 Ohm...)
    4. Different cables with different cable propagation speed

The above pictures shows the benefit of using the AVERAGE mode (cyan), instead of the LIVE mode (green). The random peaks get filtered out and the spectrum gets much more readable.

All in all, I am still fascinated by the results, even if just for educational purposes. It makes learning RF so much more interesting and hands on.

Considering that the required equipment costs less than 100 Euro, there is no excuse for not doing some real experiments.

I am now looking for some theory to explain the non-linear curve, as I imagine that it might be non-linear for other reasons than the ones I listed. If I would better understand how to extrapolate the cable length, I would try to implemente a REFLECTOMETER feature in my software...


Reflectometer measurements with the SMA Spectrum Analyzer


I just did some trials to use the SMA Spectrum Analyzer as a reflectometer using my software (see previous post).

You need:

  • 1x SMA Spectrum Analyzer 138MHz-4.4GHz
  • 1x Noise Generator - I used the cheap BG7TBL one (20 Euro at eBay)
  • Cables and adapters
The setup is shown in this picture:

Using my software, the reflected patterns can be shown in the spectrum:

The patterns are characteristic to the location of the cable fault (i.e. a not properly terminated cable).

Measuring the distance between the "valeys", you can determine the location of the cable fault, if you know the cable propagation speed. The above pictures shows a non-terminated cable with  600mm length.

This picture shows the pattern of a non-terminated cable with 2300mm length.

This resulted in the following measurements:

57 MHz > fault at 2300 mm
200 MHz >  fault at 600 mm

Using simple math, we can calculate the location of a cable fault at unknown distance, measuring the frequency-width of the "valley". Note that this requires that the cable to be measured has the same cable propagation speed as the cables used for determination of the calculation factor.

I am considering a calculation button on my software... Does this interest anyone?


Saturday, 20 August 2016

SMA Spectrum Analyzer Software available for download!


You can now download my SMA Spectrum Analyzer software from here:

Chrome will complain that it is a "dangerous file" and block it. You can, however, still access the file. To make sure you really got the correct file, please confirm the CRC32. It should state 9C6CD1E3.

To run the application, you will need an activation code. Upon the first run, the system code is automatically copied to the clipboard and should be sent to be by e-mail (address shown in the software).

For now, I am giving away free temporary licenses.