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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. ...
tomnexus's user avatar
  • 11.4k
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 ...
Marcus Müller's user avatar
7 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 ...
hotpaw2's user avatar
  • 13.4k
6 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 ...
erik's user avatar
  • 76
5 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 ...
Thomas's user avatar
  • 744
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 ...
Glenn W9IQ's user avatar
  • 18.6k
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 ...
hotpaw2's user avatar
  • 13.4k
4 votes

Is the noisy spectrum from 20MHz to 330 MHz normal?

The 0-300 MHz spectrum is full of strong signals, but it should be at least half empty, meaning that in many places an instrument with excellent selectivity would not see anything above thermal/...
tomnexus's user avatar
  • 11.4k
4 votes
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Is the noisy spectrum from 20MHz to 330 MHz normal?

Is this expected? This is actually better than many people would expect, yes, assuming the floor at ca -130 dBm/300 Hz ~= -153.5 dBm/Hz is mostly thermal noise + spectrum analyzer noise temperature. ...
Marcus Müller's user avatar
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 ...
OH2FXN's user avatar
  • 968
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 ...
Glenn W9IQ's user avatar
  • 18.6k
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 ...
Phil Frost - W8II's user avatar
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 ...
Marcus Müller's user avatar
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 ...
Marcus Müller's user avatar
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 ...
S H's user avatar
  • 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. ...
tomnexus's user avatar
  • 11.4k
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 ...
Kevin Reid AG6YO's user avatar
  • 24.6k
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.
Marcus Müller's user avatar
1 vote

What cause the spectrum peak of `center frequency`?

Every SDR has this "DC spike" more or less visible. In GNU Radio there are the blocks "Remove DC Spike" and "Remove DC Spike Auto Sync" for suppression. The respective ...
chrboesch's user avatar
  • 111
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 ...
Jack0220's user avatar
  • 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 $...
Jack0220's user avatar
  • 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 ...
natevw - AF7TB's user avatar
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 ...
user17178's user avatar
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 ...
Marcus Müller's user avatar
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 ...
Marcus Müller's user avatar

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