Could a SDR (Software Defined Radio) be used as a Spectrum Analyzer?

Thread Starter

Beetle_X

Joined Nov 2, 2012
52
I would like to build a budget lab to mostly study electronics at this point. A real Spectrum Analyzer may never actually be needed or be affordable. I was reading about SDR's and they have what looks like a Spectrum Analyzer computer program to tune it. There are also products like 'RF Explorer' and Arinst SSA-TG LC R2 which can be seen here. ebay listing and RF Explorer site. RF Explorer


Arinst says that quote
"
Limitations

The spectrum analyzer Arinst SSA-TG LC R2 is not a measure gauge, as it does not have an approved pattern of the measuring equipment. The approval of pattern of the measuring equipment has had a negative effect on the availability and price of the device. For this reason the spectrum analyzer is officially considered a field indicator. However, the device fully meets all technical requirements. Each device is calibrated against the power and frequency."

So any ideas if these would have any capacity of a real Spectrum Analyzer? Thanks in advance!
 
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sparky 1

Joined Nov 3, 2018
138
Scope with 70Mhz or more dual channel 1Gs/s has FFT and function generator for $350 is a good deal. The samples per second gives you a hint about
resolution. A slow sample rate cannot show the details. Having everything together compact sets up quick and goes anywhere, gets put away safe keeping. However having less is better than nothing. You get what you pay for. An SDR for FFT might be adequate for seeing whats out there (in the frequency domain). Lets say you build an oscillator the wave looks fine but on the low sample FFT fine adjustment may be off. As you adjust back and forth the FFT does not change. If you had the higher resolution the details are seen and adjustment can be more accurate.
 
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SamR

Joined Mar 19, 2019
2,047
Some time ago, I was using Ham Radio Deluxe with the Icom R-75 receiver. Which is somewhat like SDR as the HRD resides on the computer and controls the R-75 (or many other radios with a computer link) through an RS-232 link or USB. Most all-band receivers in the US however have some FCC defined "blind spots" where they are not allowed to receive on those frequencies. Typically cell phone frequencies and such. The nice thing was you could define the bandwidth to scan on the computer and the link would very quickly run the radio through the frequencies and mark the active areas on a screen display. Haven't used it in a few years now and there are surely better products available that have the waterfall band displays for all activity found. That uses an external antenna which, in my case, was a long-wire antenna with a preamp/antenna matching tuner feeding its signal to the radio. Analyzers are more designed for sniffing closed systems by inserting themselves into the transfer cable and monitoring the signals on that cable. Whereas the SDR is sniffing the open atmosphere by using tuned antennas to gather its signals and using software to control the SDR and feed its signal into the computer for audio and visual display. I have one on order but haven't used one as yet. Will be interesting to compare the SDR vs. all-band receiver.
 
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