13
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.
...
- 12.2k
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 ...
- 17.4k
7
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 ...
- 86
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 ...
- 13.6k
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 ...
- 754
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 ...
- 18.6k
4
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 ...
- 52.5k
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 ...
- 13.6k
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/...
- 12.2k
4
votes
Accepted
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.
...
- 17.4k
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 ...
- 968
3
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. ...
- 12.2k
3
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 ...
- 17.4k
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 ...
- 18.6k
2
votes
Using an RTL-SDR as a spectrum analyzer
It's possible and there are tools out there to aid you in this.
E.g. Please see [RTLSDR-Scanner][1] which describes itself perfectly:
A cross platform Python frequency scanning GUI for USB TV dongles,...
- 872
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 ...
- 17.4k
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
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.
- 17.4k
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 ...
- 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 ...
- 371
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 $...
- 371
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 ...
- 7,469
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 ...
- 11
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