Questions tagged [rfi]

Use this tag for questions regarding RFI (Radio Frequency Interference).

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2answers
463 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 ...
4
votes
6answers
533 views

Cordless phone consistently experiencing RFI

I've tried several cordless phones (most recently KX-TG570), and all seem to frequently pick up terrible RF interference. I have a neighbor that is a ham enthusiast, with large antenna masts on the ...
29
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6answers
33k views

Can I reduce RFI/noise at the antenna?

Recently, the power was out in my neighborhood for an extended period of time. I fired up my HF rig using battery power and was amazed at the lack of noise across the HF bands. When the power grid ...
2
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1answer
62 views

Reducing cross-band noise from plasma TV

I have a noise problem on 40, 20, and 15 meters originating from the plasma TV I own. Turning on the TV raises the noise level by 2–4 S units, depending on the frequency. The TV is located below the ...
7
votes
2answers
150 views

Apps and or equipment needed to document local interference?

A neighbor ham user recently started doing something that causes very noticeable feedback/buzzing in AM radio as well as any device that uses a wired microphone (such as a gopro with wired mic). ...
3
votes
2answers
111 views

Why am I receiving a local tv channel on a CMB frequency

I am using a simple Baofeng H6 dual band radio and I programmed weather channels. Well, on frequency 161.77500 I am actually picking up WGN, a local tv network. This frequency should be reserved to ...
0
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2answers
91 views

Identifying type of RFI by waterfall

I'm trying to identify the type of RFI I'm seeing on the waterfall in the picture below. It occurs mainly at night, every night, starting at about 6:30 p.m. and ending in the morning, and I have yet ...
1
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1answer
99 views

Can ham radio interfere with LTE wireless internet signal?

I know that there is another thread that asks a similar question however the questioner there had DSL internet, so I think my question is sufficiently different to warrant a new thread. (Can my ...
33
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14answers
30k views

Can my neighbor's ham radio antenna be interfering with my internet signal or is my internet provider just throwing blame elsewhere?

My internet provider is telling me that an antenna on my neighbor's house, which he called a ham radio antenna, is interfering with my DSL internet signal. I'm not tech savvy at all, beyond what's ...
2
votes
1answer
136 views

Unknown signal on 446MHz LSB (possible RFI?)

I am attempting to hunt down many sources of RFI in and near the UHF amateur bands at my home, but I stumbled across a very specific one that I have definitely never heard before. This one sounds less ...
0
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2answers
117 views

How should I go about finding the transmitter or antenna of a radio signal?

This site gets many questions about people trying to track down RFI, or interesting signals picked up on radios. Often the exact location of the transmitter or the antenna would be a valuable clue to ...
1
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1answer
71 views

Can sound generated by interference of cell phone signals contain any useful data?

When a cellphone is near an electronic device with speakers and someone's calling, we may hear a sound like this due to interference: Cell Phone Interference Sound Can we obtain any useful information ...
9
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3answers
1k views

How can I get rid of RFI coming from my house solar panel inverter?

The solar system on my house creates horrible rfi on all hf bands during the day when the sun is out, it goes away when it's not sunny. Any one got any ideas how to get rid of the rfi ? I already ...
2
votes
2answers
76 views

Building a low-power simple RF frequency (433MHz or 900MHz (but not both)) detector effective at 5m with a 10mW signal

I am looking for a simple schematic for building an effective RF detector which can trigger a GPIO. The goal is to (passively?) detect a 10 mW RF signal (10% duty cycle) and have that raise voltage on ...
2
votes
0answers
58 views

Checklist for QRO remote setup

In a few weeks I'm hoping to set up a solid state linear amplifier at a remote shack that I've set up at the house of a friend who lives in a rural area. I've been connecting to this shack remotely ...
2
votes
1answer
112 views

Receiving an Coded Odd Signal at 137.25MHz but don't know what it might be. It can affect my detection on NOAA 19. Need help

I am a newbie trying to detect NOAA 15, 18, and 19 satellites, which have downlink frequencies between 137 MHz and 138 MHz. I am using an SDR dongle and attached a photo of it to this post. Of course,...
5
votes
2answers
80 views

How does a digital demodulator know which level it is reading?

I have recently started getting into wireless digital communications and I read about QAM modulation. But I am a little confused as to how the receiving demodulator would know which symbol it is ...
2
votes
1answer
69 views

RFI from radials

Helping a friend with his RFI problem. He has a SDR HF radio and Hustler BTV antenna with a toroid choke and about 32-radials. He has vertical bars on his panadaptor around 20 khz apart, mainly on 40M....
1
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2answers
229 views

Hunting RFI with bars every 61 khz

I realise there have been many great posts on hunting RFI, i've got pretty close to tracking mine down, but would appreciate some insights from the ham.se experts :) I've done quite a lot of work to ...
19
votes
2answers
9k views

How to detect common-mode currents or “RF in the shack”?

Let's say we already know that if your antenna is not suitably constructed or connected then you can get current on the shield of your coaxial feed line which will flow through the shielding/grounding ...
3
votes
5answers
661 views

Do chokes at the antenna feedpoint stop the coax from receiving signals as well, or just transmitting?

It seems common knowledge that a choke at the antenna feedpoint stops the outside of the coax shield from radiating when transmitting into the antenna. But what about stopping the outside of the coax ...
1
vote
1answer
60 views

What is the maximum antenna cable length allowed in GNSS application?

I am beginner in designing GNSS receiver design and facing concern while testing the high precision GNSS survey.I am using GNSS survey grade antenna for my GNSS receiver application testing, the ...
1
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3answers
108 views

What is the name of a device used to detect noisy appliances?

I live in an apartment. I don't have control over all of the appliances but perhaps I can mitigate if I know where the noise is coming from and under what circumstances. If I'm shopping for such a ...
3
votes
2answers
133 views

What kind of RFI is this?

I'm getting a lot of noise now that I have a dipole higher up. The pattern on the waterfall makes it seem man made. Could it be power line? Or is it some kind of motor? Here's a short video of the ...
0
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2answers
47 views

How Duty cycle affects transmission rate in RF module?

I planning to use RF module for communication of high precision GNSS module. So I am doing detail study on RF module. In one of the datasheets of RF module (part no: RFD868ux) mentioned that 'Duty ...
2
votes
0answers
56 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 ...
11
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2answers
4k views

How to reduce RF in the shack when using vertical HF antenna (no radials)

What can be done to reduce RF in the shack (riding back along the coax) when using a vertical 10M antenna (without radials due to space constraints)? The antenna is an IMax-2000 at 32' elevation (20' ...
4
votes
2answers
322 views

Using an SDR on a Laptop with Noisy Power Supply

I'm going to start this off by saying I'm very new to this and I don't really know a lot so any detailed information would be much appreciated. I have just started using an SDR (a cheap RTL model) ...
1
vote
1answer
180 views

Need a ferrite suppression material for choking 15 kHz to 60 kHz

Electric fence RFI is ruining reception on our VLF lightning receivers, and we need a material to place around neighbors' fence wires to suppress the noise being radiated. Preferably, a split bead, ...
3
votes
3answers
91 views

Method to generate PIM

I would like to have a go at measuring PIM. ( Passive Intermodulation ) in UHF. To test my ability to measure PIM, I need to find something that generates PIM. I either envision a 50Ω device that ...
3
votes
0answers
196 views

The whole neighborhood's internet drops when I transmit on 40M

I recently built a vertical. It's 6M radiator, a coil, and 1.2M more of radiator. It sits on my roof, which is metal, and acts as a ground plane (GND from the feedline is connected to it). There is a ...
3
votes
2answers
1k views

How does FM station have fixed frequency when FM modulation changes the frequency?

I am not sure if this question fits better in physics.stackexchange or ham.stackexchange, feel free to correct me. I am new to studying RF and SDR in general, I was looking up how modulation works and ...
10
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3answers
2k views

My neighbor is complaining about my transmissions, what can I do?

My neighbor has indicated that they can hear noise from their computer amplified speakers when I'm transmitting. We've done a few tests and it does appear that it's my transmitter that's causing the ...
5
votes
2answers
232 views

Wide band TX capable band-pass filter for VHF and Airband

I want to share the same antenna for VHF (TX/RX 144-148 MHz) and for Airband RX-only (116-136 MHz). I live on a very congested area where filter is a must, so I'm looking for the best solution for my ...
1
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1answer
103 views

144Hz monitor with freesync noise on 40m

When I tune on 40 m (7.074 MHz USB as test frequency for there's FT8) and turn on my PC with a monitor that's 144 Hz refresh rate and has freesync on, it starts to make noise and makes signals almost ...
3
votes
2answers
202 views

HDMI to VGA adapter interference with 138.5 MHz carrier

(sorry for my English) I'm using the HDMI to VGA adapter on my pc, and receiving weather satellites on ~137 MHz with RTL-SDR V3. There was a problem: my VGA adapter creates a powerful signal, who ...
8
votes
1answer
184 views

Identifying regulations for interfering stations

I'm working on tracking down some 2m repeater interference, and I have identified that the offending signal is a spur transmission on a commercial pager service (that lands right on our repeater input ...
2
votes
3answers
603 views

What causes my direct conversion 80m receiver to receive AM broadcasts?

I am making a Direct conversion receiver from this circuit at this website. I made it for the 80m band and I changed: The frequency of VFO to about 1.75 MHz L1 and L2 to a bandpass filter for 80m ...
0
votes
1answer
47 views

What are the most common EMI blockers for household computer cords, monitors, etc.?

Ferrite beaded cords, and especially double-sided ferrite beaded cords, seem especially uncommon. Are there other, perhaps more effective ways, which I should be minimizing the EMI of my overcrowded ...
1
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2answers
117 views

Will my neighbor's amateur RF antennas effect my own utilities?

I am buying a house in the UK and the property next door has two poles for antennas. The next door lady seems to be very nice person and said her husband is an RF engineer and he used these on ...
7
votes
4answers
588 views

DIY SA612 + RTL-SDR HF receiver: good on laptop, but huge wideband noise on Raspberry Pi

I recently built a SA612 mixer for HF reception. I used an USB-frequency oscilator to shift the incoming frequency up by 28.8 MHz. I used a random wire antenna outside my balcony and connected it to ...
2
votes
4answers
773 views

What has happened to HF?

Has the HF spectrum become noisier over the decades due to man-made interference? Is this a reason why HF band activity appears to be declining?
6
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2answers
77 views

Can an ultra-wideband system transfer data at high speed without precise clock synchronization?

Recently, ultra-wideband technology has been in the news again. From the Wikipedia article: UWB transmissions transmit information by generating radio energy at specific time intervals and ...
1
vote
1answer
84 views

New quad-band mobile receives while transmitting?

I've got a week-old TYT TH-9800, a quad-band (10/6/2/70cm) mobile, Chinese knock-off of a Yaesu HT-8900. So far, I love it -- several times the power of my HT, and a better antenna actually outside ...
1
vote
2answers
104 views

Audio being sent over ground pin on audio jack

I just bought a QYT KT-8900D mobile radio. One of the first things I've noticed is that I cannot use my mixer to completely lower the volume of the radio's 3.5mm TRRS output. When the fader is all the ...
1
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0answers
62 views

Can my neighbors ham radio station be preventing my TV antenna from proper reception? [duplicate]

I have a winegard 8200 series antenna and it worked flawlessly in getting me reception of more than 70 stations. The wind blew it down and I couldn't replace it for about 6 months due to the fact that ...
8
votes
4answers
2k views

Real world performance of magnetic loop antennas?

I was investigating about magnetic loop antennas. In a paper about them I found some bold claims: and This almost sounds too good to be true, considering a lot of us hams are surronded by city noise ...
5
votes
3answers
508 views

Only noise, no signals whatsoever on HF

Last night there was a power outage at home. I was able to see a LOT of stations on 20M (FT8). As soon power returned, all of them disappeared. You can see in the waterfall very clearly when power ...
2
votes
1answer
88 views

Should I run RG8x / mini8 zip tied to a cat 5e ethernet cable?

I'm running a feed line from the end of my amplifier to the antenna for HF transmissions. I'm using RG8x / mini 8. There's an existing pathway through my house I'd like to use that has a cat 5e ...
3
votes
3answers
512 views

What is RF hash?

Ok, I get that "RF hash" is some sort of slang for "RF interference" (think CB), but does it refer to a particular type or source of interference? Do tell.