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Sunday, 19 February 2017

VMA Simple Spectrum Analyser: New automatic Channel Power Measurement!

Hi,

After implementing the Automatic Bandwidth Measurement, I thought "why not implement the Channel Power Measurement, too?".

Well, here it is:


Very simple to use: if you activate just one of the three Bandwidth Measurements (at -3dB, -6dB or -60dB), the resulting channel power is calculated and displayed.

To make this easier to analyse, the area contemplated for this measurement is painted in purple colour.

The channel power displayed is the summed power of this area, according to the formula:


Update:

I did some measurements with the Siglent SSA3021X and the Deviser S7200, to get an idea of the Channel Power Meter Measurement precision.

Here are the results:

Picture 1: Channel Power Measurement carried out with the VMA Simple Spectrum Analyser. I get at -6dB bandwidth a channel power of -47.8 dBm.

Picture 2: Same measurement carried out with the Siglent SSA3021X. Channel power is measured at -52.08dBm.

Picture 3: Using the Deviser S7200 TV Analyzer, this picture shows the spectrum, which looks exactly like the ones obtained in the previous two pictures.

Picture 4: The measurement screen of the Deviser S7200 shows a channel power of -48.3dBm.

Conclusions:
  1. The overall difference in readings of around 4dB results from different factors like:
    • Varying signal power due to live transmission.
    • Different connectors/adapters.
    • Intrinsic errors.
    • Measurements carried out at different RBW: the first picture shows my measurement at 100 samples - if I increase it to 1000 samples I get a slighly higher channel power reading, due to the higher resolution.
  2. The VMA Simple Spectrum Analyser allows fairly accurate channel power measurements at an incredible price, considering how much the ADF4350/ADF4351/MAX2870 devices cost.

Cheers,
Vitor

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