Questions tagged [noise]
Questions about noise in the sense of that inevitable component of any real signal. For questions about avoiding or eliminating interference from manmade sources, use [rfi] instead.
63
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Pulsing static on 6m
Located in Illinois, US, I recorded this http://loami-windmill.com/sounds/6m_noise.m4a on 28-June-2023 at 1603 UTC on 50.074MHz USB. The static has regular "pulses" where it gets slightly ...
- 929
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Noise power with and without antenna
I have designed a receiver at 440 MHz with a 10 MHz signal bandwidth. I have measured the sensitivity of the receiver in a cabled setup (coax cable between transmit and receive) and that is about -93 ...
- 11
5
votes
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113
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Why does my received power rise so much when I connect an antenna?
I am in early stages of making a narrow-band radio receiver (block diagram below). To give you an idea, I am using a simple CP-FSK based modulation scheme, and have achieved 5dB SNR with a Tx signal ...
- 153
2
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2
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118
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Is the noisy spectrum from 20MHz to 330 MHz normal?
I have recently been testing some VHF/UHF antennas for reception in my Lab, and have noted something I could not explain. Following are the spectrum plots captured on our R&S FSV spectrum analyzer,...
- 23
4
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2
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166
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Are there any modes that use pseudo-random noise codes to "amplify" signals?
GPS for example uses them to allow receivers to decode extremely weak signals far below the noise floor.
From https://blank005.tripod.com/gps/psedo_random.html :
If we tuned our receivers to the GPS ...
- 93
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0
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152
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What is this noise on 6m?
I'm trying to figure out what an S8 noise source is on my 6m band. I already turned off all the breakers in my house, and it only reduced to S7.5 noise, so there is a small interference from my home, ...
- 438
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168
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Link budget validation for a UHF satellite ground station
I built a UHF satellite ground station. It has a yagi with G=16.1dBi and an LNA with G=20.1dB. It’s a 430 - 450 LNA with NF=0.68. The RF cable, rg174/u has I think close to a 1dB/m, which would mean ...
2
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327
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High electrical noise only when coax shield is connected
I'm trying to understand a noise issue on my Yaesu FT-891. I have very high 60 hz electric buzz on most bands with 40 and 15M being the worse at about S9+. My antenna is a MyAntennas 66ft EFHW fed ...
- 21
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91
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Why so high values of noise température of a spectrum analyser?
We know that the displayed average noise level(DANL) and noise figure(NF) of a spectrum analyser is given by the following equation:
\begin{equation}
NF_{𝑆𝐴} = 𝐿_{𝐷𝐴𝑁L}[dBm] + 174dBm −10 \cdot ...
- 165
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64
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How do you take into account the SNR of a transmitter in a fade margin?
I have a fade margin for a RF bridge, but it only compares the sensitivity of the receiver to the received power - or alternatively calculates the Eb/N0 from the net received power divided by the ...
- 153
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3
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246
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Ignition Static on 2m mobile but not 70cm
I have an ICOM 2730a 2m/440 mobile rig in a 2015 Ram 1500. Tx and Rx with truck not running is excellent. With engine running I hear static popping, but only on 2 meters. If I Tx I can hear the ...
- 11
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107
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How to analyse the distribution of the noise being received by my RTL-SDR device?
I'm very new to RTL-SDR and signal processing in general, but have managed to get my device (NOOELEC NESDR Mini) working and data into Python (via the pyRTLSDR library).
I am able to output a complex-...
- 101
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What are the unintentional radiation limits in U.S. HF bands?
What are the radiation limits in U.S. HF bands in terms, not in terms of uV/M, but in dBm or uV levels transmitted though an HF dipole antenna? I assume that if the antenna is connected to a receiver ...
- 13.1k
4
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7
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3k
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QRN: How to chase down a solid S9 noise floor on 40m only
I am new to this, having just set up my station. I have "very bad" QRN on 40m: S9. Here is the setup:
High density suburb with flats and houses
Yaesu FT450D with fan dipole at 6m-9m above ...
- 233
3
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1
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251
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Why is QRN so bad on the low HF and MF bands?
If one tunes an HF/MF radio at night, the lower the frequency (or the longer the wavelength) of the band, the more QRN (static and atmospheric noise) there is. 80m is noisier than 40m, and 160m is ...
- 9,122
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933
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If receive performance doesn't depend on SWR, then how can I tune my manual HF antenna tuner by band noise?
The popular question "What is the relationship between SWR and receive performance?" asks if a receiver with a well-matched antenna (low SWR) beats a receiver with a poorly-matched antenna, ...
- 9,122
2
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3
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223
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Where to find QRM and/or QRN audio files?
I'm looking for some QRN/M audio files to "show" someone what said noise can sound like, particularly interested in static crashes or lightening bursts. Have Googled same with no joy other ...
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151
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How to track down and neutralize this apparent mixer creating noisy emissions around my signal?
When I transmit, it there seems to be something mixing and reflecting my signal.
For example, when I transmit on 14.300 MHz, I see signals above my transmitted signal at at 14.500, 14.700, 14.900, etc....
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114
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Buzzing FM interference
What kind of interference or other receiver issues can cause a constant buzzing noise (picket fence lines in the audio spectrum) in the demodulated audio of a received NFM VHF signal?
With AM, it ...
- 13.1k
4
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1
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410
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Easy Digi hum with isolated ground
I am creating an Echolink simplex link using a Raspberry Pi 3 B+, a Pluggable USB sound adapter, and an "Easy Digi" sound card interface which has 2 - 600ohm isolation transformers for audio in/out as ...
- 43
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437
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Extremely strong QRM on VHF?
I don't usually operate in 2 m, save for FM satellites. I usually go to a nearby park when I do this, for better view of the horizon. But I tried working them from home for the past couple of days, ...
- 1,199
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189
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Working satellite on 2 meters, at what arc distance to sun (center) will noise floor be problematic to a disruption of a communication path?
Is there some simple utility, or published set of charts, or suite of formulae, where one can approach the situation by inputting a space weather summary, (sunspots, various indexes, etc), the receive ...
- 247
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371
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Icom 7300 low frequency broad-spectrum noise
What's causing these horizontal bands of noise?
It's the middle of the day here in a low density city neighborhood.
They were not present about 20 minutes ago; now they are even stronger and filling ...
4
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2
answers
660
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What causes the light and dark bands (of background noise) in an HF waterfall display?
While monitoring the 40-meter band (among others) throughout a typical day/night as propagation changes I have noticed there are often bands of very low noise (black area) and others with much higher ...
- 138
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2
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852
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What is Spectral Subtraction for noise reduction?
I previously asked a general question about noise reduction, but none of the answers mentioned this specific method or algorithm. (the noise reduction button on some radios and DSP software seems to ...
- 13.1k
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235
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What does a receiver's noise reduction function do?
Some receivers contain a noise reduction button or function.
What does this noise reduction do?
Is there more than one type of noise reduction?
How does the circuit or software know what part of ...
- 13.1k
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0
answers
280
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Uplink-limited vs. Downlink-limited
What is the definition of these terms? Would a system with signal to noise ratios of uplink 100dBHz and downlink 80dBHz be downlink-limited?
- 11
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43
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Noise Floor when receiving Es'hail 2
I'm currently trying to receive the Es'hail 2 satellite using a standard TV LNB, 60cm dish and RTL-SDR. My dish is slightly offset by 2 degrees, and my SNR is only about 15dB unfortunately.
My main ...
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762
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Does a loop antenna have less susceptibility to atmospheric noise than an open ended antenna?
I always get the feeling that an antenna which has a loop for the driven element such as a folded dipole or quad will pick up less static or 'high impedance' noise than an antenna that has free ends ...
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2
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584
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Noise reduction
I live close to an AM transmitter broadcasting in the kW of power. My RTL SDR dongle gets very overloaded. Using 2 AM broadcast filters, I have mostly managed to stop the overloading, at least from ...
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How does lowering the RF Gain help with SNR?
Let's say for sake of example we are in the 40m band.
I've read articles and posts about riding the RF gain (or even just simply lowering it). And I can see how it is useful in overload situations.
...
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2
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3
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Doublet with ladder line vs coax w.r.t. noise
I live in the city, with 50’x 100’ lots. I use an 80 meter doublet at 30 feet, fed with ladder line to a tuner. My noise floor ranges from S5 to S9 depending on the time.
Would a coax feed reduce ...
- 21
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289
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Measuring S21 against TX-RX distance (a.k.a path loss modelling) with a network analyzer didn't give expected results
Task: Path loss modelling
Target frequency: 433 MHz;
Laboratory environment: in a basement where there were other equipment and metal shelves. A few acoustic absorbers were placed around the setup.
...
- 57
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2
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1k
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High Noise Floor on 40/80m at Night
I've notice a couple of times over the past couple of weeks that the noise floor, particularly on 40 and 80, is exceptionally high as the grayline passes me into night. I'm looking at the general band ...
- 173
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What's the Noise Floor?
What's the noise floor according to this picture?
Is the noise floor S5 as it shows in the Signal meter at the top right or is it S1 as it shows on the panadapter?
The reason why I ask is I'm trying ...
- 173
5
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1
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188
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How do I have a full signal of noise on a handheld?
I'm new to ham (although I've had a license for a long time) and I'm having issues with receiving on a basic handheld. I have a cheap BaoFeng UV-82HP and I keep getting full signal noise at random ...
- 153
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2
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237
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What can I do about my strong RF noise?
I have a problem with strong and constant received noise, from S7 to S9+20.
I've shut off the power, both in my house and two neighbors' houses.
I took my portable rig with a Hustler antenna and ...
- 21
9
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3k
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High 40m noise floor during the evening but quiet in the afternoon
I've been dealing with S7 static on 40 meters ever since I got started a few weeks ago. It's so bad that I have to use my RF ATT so that the static is not deafening.
I did some research about ...
- 781
5
votes
5
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890
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Signal path to maximize RFI rejection in an urban environment
Urban ham here (Cambridge, MA - FN42ki - KC1JZE) looking for tips to make this hobby possible in the city. I rarely can hear both sides of HF phone transmissions, and have yet to make contacts despite ...
- 185
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Rolling QRM from 3000-10000 kHz - What Is It?
Video
I was lucky to catch the QRM start this morning @ approximately 10 AM Pacific Standard time. It was wide, starting around 3000 kHz up to 10000 kHz.
It starts fast then slows to a crawl. The ...
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How can I calculate the effects of an LNA, antenna gain, etc. on noise performance?
There are many things I might do enable my station to hear weaker signals that would otherwise be buried in noise. Just a few possibilities:
Install a nice LNA
Increase antenna gain
Reduce feedline ...
- 51.4k
3
votes
2
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202
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Accounting for feedlines in noise temperature calculations
In writing an answer to "Use noise figure and gain to calculate weakest signal radio can receive?" I've managed to confuse myself.
I believe this much is true:
$$ T_\text{eq}
=T_1
+{T_2 \over G_1}
+{...
- 51.4k
4
votes
2
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268
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Use noise figure and gain to calculate weakest signal radio can receive?
An FM radio receiver, using a 1 kHz tone at 3 kHz deviation has a 12 dB SINAD (Signal To Noise and Distortion) of -116 dBm.
I would like to increase the 12 dB SINAD sensitivity of the receiver to at ...
- 7,550
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1
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1k
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What are these continuous sine wave tones I keep hearing?
I'm messing around on WebSDR and by just scanning through I sometimes come across these continuous tones in USB. One in particular was 28.800 MHz USB.
I've picked them up on nearly every WebSDR unit ...
user11031
3
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1
answer
422
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How can I determine if out of band interference is affecting my AIS reception?
AIS
I am receiving ship AIS messages. These are low power, digital messages periodically sent on two marine channels close to 162mhz. This frequency is surrounded by FM broadcast, weather radio, and ...
- 229
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6k
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Is 20m noisy, or do I have a lot of local interference?
I'm making my first ventures into HF with a Yaesu FT-450D and a homebrew 20 Meter inverted-V antenna a local ham helped me set up.
I've noticed that the 20 Meterm band seems to have lots of ...
- 371
3
votes
2
answers
5k
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Baud rate/frequency/bandwith/characters per second
I'm trying to filter a noisy serial line that comes in to a radio (mostly as a thought excercise in line filtering).
The data comes in on a RS-232 line, 9600 baud, 8n1.
I've found a lot of ...
1
vote
0
answers
41
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Determining if what's on a frequency is signal, or noise [duplicate]
I have the spectrum binned into 5kHz bins. For each bin, I'd like to determine (via software) whether what's in that bin is primarily signal (an FM broadcast station; a ham repeater) or noise (just ...
5
votes
5
answers
5k
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HF Noise Level S5 to S9+18
Since I got my HF radio a year and change ago, I've been able to hear very little except noise and the WWV time station on 10MHz. Noise seems to vary by band, but not how I'd expect:
80m: S7-S9
40m: ...
- 803
11
votes
1
answer
2k
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Is FM modulation still more resistant to noise when given the same bandwidth as an AM signal?
FM modulated radio is much more resistant to noise and can deliver better sound quality than AM radio. But FM signals also use more bandwidth than AM signals. In general a wider bandwidth signal is ...
- 405