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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.

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Why are there weird sounds in radio?

When I'm tuning through the radio on HF, suddenly, I hear a tone. So, I tune back, and the more I tune back, the more the tone changes pitch. For example, if I tune back 1 kHz, the sound rises by 1 Hz....
o'o's user avatar
  • 513
1 vote
1 answer
98 views

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 ...
Duston's user avatar
  • 939
2 votes
1 answer
153 views

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 ...
Malik 's user avatar
  • 21
5 votes
1 answer
128 views

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 ...
Kraken's user avatar
  • 153
2 votes
2 answers
152 views

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,...
Asad Ul Haq's user avatar
4 votes
2 answers
199 views

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 ...
2080's user avatar
  • 93
1 vote
0 answers
235 views

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, ...
User5754448's user avatar
2 votes
1 answer
242 views

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. Itโ€™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 ...
Moses Browne Mwakyanjala's user avatar
2 votes
1 answer
481 views

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 ...
Don James's user avatar
0 votes
1 answer
169 views

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_{๐‘†๐ด} = ๐ฟ_{๐ท๐ด๐‘L}[dBm] + 174dBm โˆ’10 \cdot ...
Pierre Polovodov's user avatar
0 votes
0 answers
83 views

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 ...
Mister Mystère's user avatar
1 vote
3 answers
360 views

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 ...
PappyD's user avatar
  • 11
0 votes
1 answer
150 views

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-...
Kris's user avatar
  • 101
1 vote
1 answer
67 views

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 ...
hotpaw2's user avatar
  • 13.5k
4 votes
7 answers
4k views

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 ...
Oliver Schönrock's user avatar
3 votes
1 answer
306 views

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 ...
rclocher3's user avatar
  • 9,242
6 votes
6 answers
1k views

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, ...
rclocher3's user avatar
  • 9,242
2 votes
3 answers
255 views

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 ...
Dennis's user avatar
  • 21
4 votes
1 answer
185 views

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....
Rosa's user avatar
  • 191
2 votes
1 answer
123 views

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 ...
hotpaw2's user avatar
  • 13.5k
4 votes
1 answer
557 views

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 ...
john8791's user avatar
1 vote
0 answers
501 views

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, ...
hjf's user avatar
  • 1,219
4 votes
2 answers
201 views

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 ...
always_learning's user avatar
2 votes
1 answer
509 views

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 ...
x-ray_kilo_india_uniform's user avatar
4 votes
2 answers
746 views

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 ...
Josh's user avatar
  • 138
3 votes
2 answers
1k views

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 ...
hotpaw2's user avatar
  • 13.5k
5 votes
1 answer
279 views

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 ...
hotpaw2's user avatar
  • 13.5k
1 vote
0 answers
299 views

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?
openloop's user avatar
2 votes
0 answers
44 views

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 ...
user14615's user avatar
  • 157
5 votes
2 answers
919 views

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 ...
Andrew's user avatar
  • 3,693
1 vote
2 answers
638 views

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 ...
user14615's user avatar
  • 157
4 votes
6 answers
4k views

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. ...
Paul's user avatar
  • 781
2 votes
3 answers
2k views

Doublet with ladder line vs coax w.r.t. noise

I live in the city, with 50โ€™x 100โ€™ 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 ...
Steve's user avatar
  • 21
1 vote
1 answer
332 views

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. ...
luw's user avatar
  • 57
1 vote
2 answers
2k views

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 ...
Etep - VE6ETP's user avatar
1 vote
1 answer
420 views

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 ...
Etep - VE6ETP's user avatar
5 votes
1 answer
192 views

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 ...
Eric Fossum's user avatar
1 vote
2 answers
256 views

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 ...
robert dale's user avatar
9 votes
2 answers
3k views

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 ...
Paul's user avatar
  • 781
5 votes
5 answers
964 views

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 ...
Jeremy Gilbert's user avatar
9 votes
1 answer
415 views

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 ...
user11702's user avatar
  • 111
12 votes
1 answer
2k views

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 ...
Phil Frost - W8II's user avatar
3 votes
2 answers
242 views

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} +{...
Phil Frost - W8II's user avatar
4 votes
2 answers
305 views

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 ...
Skyler 440's user avatar
  • 7,620
8 votes
1 answer
2k views

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 ...
user avatar
3 votes
1 answer
452 views

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 ...
hazzey's user avatar
  • 229
7 votes
3 answers
6k views

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 ...
Adam KC0DAD's user avatar
3 votes
2 answers
5k views

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 ...
Dieter Vansteenwegen's user avatar
1 vote
0 answers
41 views

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 ...
Ken - Enough about Monica's user avatar
5 votes
5 answers
5k views

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: ...
William's user avatar
  • 813