12 votes
Accepted

Why is 9 kHz the lowest frequency for spectrum analyzers?

Spectrum analysers are often specified down to 9 kHz because this is the lowest frequency of conducted or radiated emissions that is specified in the Electromagnetic Compatibility (EMC) standards. ...
  • 8,340
8 votes
Accepted

Looking for a convenient audio frequency spectrum analyzer

So, requirements: runs on OS X and windows easy to work with quicker than "tone and excel" method If you don't like writing software yourself, this should still be pretty doable with just ...
4 votes

How to measure the power emitted from an HF antenna in near-field WPT?

WPT (wireless power transfer) is typically performed using flat, multi-turn coils (inductors) as antennas. In some cases, the coils are self resonant based on their parasitic capacitance and self ...
  • 18.2k
4 votes

What cause the spectrum peak of `center frequency`?

In addition to the clock leakage mentioned in the other answer, a DC offset spike can also show up in the downmixed IQ if the mixer(s) and/or the ADC(s) aren’t perfectly balanced (exactly equal gains ...
  • 12.6k
4 votes
Accepted

What cause the spectrum peak of `center frequency`?

Internal interference in the radio. There's a clock ticking at that frequency in order to downmix the signal, and spurious emissions from that clock is being picked up by other circuitry. The clock is ...
  • 674
4 votes

How to increase the range of the spectrum analyzer in SDRSharp?

If you use SDRSharp with an Airspy Mini, instead of an RTL-SDR, the supported sample rates allow up to 6 MHz bandwidth, due to the use of an ADC with a higher sample rate than the RTL2832 is capable ...
  • 12.6k
4 votes
Accepted

Why would a VNA not make a good Spectrum Analyzer? Or an SDR a good VNA?

A VNA generally does not have to worry about a multitude of input signals as it controls its own test signal generation. A SA has to be able to show small signals even in the presence of large other ...
  • 56
3 votes
Accepted

How to increase the range of the spectrum analyzer in SDRSharp?

Unfortunately you cannot increase the bandwidth much: the sampling rate in RTL2832U is at maximum 3.2 megasamples / second. In theory (Nyquist theorem) you could get ±1.6 MHz banwidth, but that is ...
  • 960
3 votes
Accepted

Spectrum Analyzer: using "Max hold" for peak detection of a burst signal

It is important to understand that the SA takes some finite time to sweep (calculate the FFT buckets) for the frequency range in question. It is quite possible with a short duration signal that the ...
  • 18.2k
2 votes

Using an RTL-SDR as a spectrum analyzer

If you have a commercial transceiver you can reasonably assume it's free enough of harmonic distortion. You can then use that as a signal generator or a narrow-band spectrum analyzer to validate your ...
2 votes

Using an RTL-SDR as a spectrum analyzer

In principle: yes, that will work. I've never used an RTL dongle without a tuner / bypassing the same; I didn't know that was an option. But yes, as every ADC, you need to sufficiently limit the ...
2 votes

2,4GHz Spectrum Analyzer with wireless card

Probably not. Most radio equipment of this sort only gives access to the demodulated-and-decoded signal. The requirements for being an (uncalibrated) spectrum analyzer of this sort are essentially ...
  • 23.1k
2 votes

How to measure gain of an antenna?

Measuring received power is pretty straightforward. Set up a receiving antenna some distance away. Make it at least 10 wavelengths, but even farther is better. Make sure the receive antenna has the ...
2 votes

Most accurate way to measure signal power with (cheap) Spectrum Analyzer

However, depending on which options I choose on the Spectrum Analyzer, my measurements are different by up to 6-10 dB(!). Using a spectrum analyzer needs a bit of understanding what it does: it ...
2 votes
Accepted

Weird looking spectrum. FSK and ASK combo?

Since there is no visible carrier (no peak in the middle), it can not be an AM/ASK signal, which has half of its transmit power on the carrier. This leaves PSK and FSK as the likely choices. The two ...
  • 145
2 votes

Why so high values of noise température of a spectrum analyser?

A noise figure of 22 dB is pretty normal for a spectrum analyser. Expressed as a noise temperature it looks like a large number, but there are many equations which yield unexpected and large numbers. ...
  • 8,340
1 vote
Accepted

What's the negative float of rtl_power output means?

These are decibels relative to some arbitrary full-scale value. Hence, negative values denote a power smaller than that reference.
1 vote

How the ELF-VLF background noise spectrum looks like?

You don't need a spectrum analyzer for such low frequencies, more like a very accurate voltmeter that you can record over long periods. As the antenna, you will need something huge, I recommend the ...
  • 373
1 vote

How to increase the range of the spectrum analyzer in SDRSharp?

HackRF One will give you 20MHz bandwidth. Edit for more detail: If you buy the HackRF One instead of the Noelec SDR dongle, you will have 20MHz instead of 2MHz. Note that the HackRF One costs about $...
  • 373
1 vote

What determines the bandwidth of an FM signal?

Does the deviation from the center frequency depend on the frequency of the audio/information signal applied to the carrier? No. In FM terminology, the "deviation" is chosen by the designer (or ...
1 vote

Retuning 2m Duplexers (Q2330E) with Spectrum Analyzer and Tracking Generator

There is a trick to balance the notch tuning johannsen cap adjustment with the coupling ring loops to meet the required rejection per side with minimum insertion loss. I believe I tuned mine to reject ...
1 vote

Strange Noise Floor observed in UHF Band

300 kHz channel at 436 MHz sounds a lot like your spectrum analyzer might be seeing that are at twice the frequency – 872 MHz would be a typical 2G cellular network frequency, and 300 kHz might be ...
1 vote

2,4GHz Spectrum Analyzer with wireless card

In addition to what AG6YO said in his answer (No, a network card is a network card and is built to find networks, not "spurious" power of another standard) – Bluetooth as is is a protocol especially ...

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