Questions tagged [rfi]

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

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7
votes
0answers
80 views

Why are modern telephone lightning arrestors less prone to RFI problems than old ones? [migrated]

I was reading about telephone lightning arrestors in my ARRL RFI Book (first edition, copyright 1998), in chapter 9 "Telephone RFI" (by Pete Krieger, previously WA8KZH, now K8COM) and on page 9.6, the ...
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 ...
1
vote
1answer
60 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
89 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 ...
2
votes
3answers
286 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 ...
5
votes
2answers
103 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 ...
0
votes
1answer
41 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
91 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
227 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 ...
6
votes
2answers
72 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
66 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
95 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
vote
0answers
56 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 ...
5
votes
3answers
225 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
78 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 ...
7
votes
4answers
403 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 ...
3
votes
2answers
93 views

Tips for HF Antenna with house near AM transmitter

My back garden is very small - about 500sqft. I also live near an AM transmitter and requires an AM filter. I would appreciate some general tips on the best approach to receiving HF signals (Ham and ...
2
votes
1answer
126 views

Where does this common spurious transmission come from? Is there a quality difference?

I decided to see what my ham transmissions look like on an SDR and was kind of shocked to see how much leaks out. The waterfall display is split between two handhelds during transmit. There are a ...
5
votes
1answer
384 views

How to find something disrupting car key fobs across a parking lot?

Apparently there's a parking lot in which car key fobs are messing up: Key fobs that suddenly won't unlock vehicles. Cars that won't start. Alarms that go off for no reason and can't be quieted. ...
2
votes
1answer
65 views

Can an indoor antenna damage unshielded electronics?

I have a 25w radio running through a ~4.5db gain antenna. If I use a 4W HT indoors, I can hear a loud buzzing noise emmanating from my computer speakers. If I used the 25w mobile with the 4.5db gain ...
7
votes
3answers
556 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 ...
6
votes
2answers
681 views

Feed-through Capacitors

I'm in the "information gathering" phase of a RF Power Meter project and the design I fancy (W7ZOI Power Meter) calls for a feed-through capacitor at the output port. I understand that a feed-through ...
3
votes
4answers
217 views

My radio in the garage is temporarily shutting down the wifi when I key up

I have a Yaesu FT-101EE, D-104 Mike, MFJ-929 Antenna Tuner, 80-10 OCF Dipole Antenna with a MFJ balun. When ever I key up for more than a few seconds, the wifi network goes down for a couple of ...
1
vote
1answer
211 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 ...
1
vote
1answer
95 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 ...
5
votes
3answers
660 views

Is this the Correct Ferrite Core to Reduce RFI as a Common Mode Choke?

I have a Flex 3000 connected via RG-11 coax to a inverted V fan dipole tuned for 40m and 20m on my roof. I have an "ugly" balun up on the mast by the antenna. I further have the feed-line going into a ...
5
votes
1answer
193 views

Can my laptop pick up CB radio frequencies?

I was on my laptop watching a show and I paused to look something up and since there was no sound I could hear a voice talking. It sounded distorted like it was coming over a radio and I couldn't make ...
1
vote
2answers
167 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 ...
2
votes
4answers
630 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?
3
votes
1answer
232 views

What is this odd data/screeching/fuzzy signal?

I was listening to a commercial FM radio station on 100.9 MHz, and this intermittent weird sound kept coming through it. Here is a recording of it. The audio starts at about 15 seconds. It sounded ...
5
votes
5answers
409 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 ...
3
votes
1answer
442 views

Benefit to remote antenna tuner for end-fed non-resonant antenna?

Does addition of a remote feed-point antenna tuner affect the use of the coax braid as a radiator? If it no longer "radiates" in such a setup, what does? Is a shack or remote tuner better for ...
3
votes
3answers
525 views

How do active loop vs. passive loop differ in terms of noise rejection?

As a urban ham (Harvard Square, Cambridge MA), I'm on the hunt for RFI rejecting antenna configurations. After hours of research, I've come across many strong recommendations for loop antennas, since ...
2
votes
2answers
31 views

Interference difference: fixed and mobile wireless systems

I am answering some questions about my course of radio links and I came across with the question about explaining interference in fixed and mobile wireless systems. As far as I know ALL wireless ...
2
votes
1answer
69 views

How should I measure RFI on the headset cable from a hand-talkie?

I'd like to build an audio interface cable from my smartphone to my Yaesu FT-60 which incorporates VOX (since the Yaesu doesn't have VOX functionality) for APRS apps on the phone. I'm having problems ...
3
votes
2answers
233 views

Can jamming a channel with white noise be detected?

If somebody were to setup a pirate radio signal that was broadcasting static would the people tuned in to that frequency be able to tell? Assuming that there was nothing already on that frequency ...
1
vote
1answer
126 views

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

Electric fence RFI is ruining reception on our ELF lightning receivers, and we need a material to place around neighbors' fence wires to suppress the noise being radiated. Preferably, a split bead, ...
1
vote
3answers
347 views

Weird Harmonic Issue on Raspberry PI FM Transmitter

So I talked to my neighbor about my Raspberry PI, harmonics and his emergency radio. He told me to fire it up, as we saw the FCC sticker on it, meaning it is in compliance with Part 15. I started my ...
2
votes
2answers
112 views

FFT showing evenly spaced signals when tuned to ~56 MHz down to 25.680

I'm running GQRX on Mac OS X 10.11.6 hooked up to an RTL-SDR dongle. I noticed when I'm tuned anywhere between ~56 MHz on down to 25.680 MHz I see evenly spaced signals on the FFT. But when I tune ...
2
votes
2answers
778 views

How to determine the minimum distance between ham and TV antennas

I'm planning on putting a quarter wave ground plane antenna in my attic for use with 2m/70cm. In order to keep the feed line short, it needs to be near my TV antenna. Is there a rule of thumb for ...
7
votes
3answers
540 views

Attic Dipole - Impact of Ethernet over CAT5/6

I've been thinking about putting 20m and 10m dipoles up in my attic (HOA), but I also intend to soon put some Ethernet cable to a WAP (with PoE) through the attic. I was intending to feed this with ...
3
votes
3answers
362 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.
3
votes
3answers
436 views

Suggestions for mounting a mini-whip as high as possible

I've ordered two mini whip antennas from Ebay (Russia) for HF and MW. As power lines cross my city property in a L shape - the only way to get away from them is to go up. So I'm hoping that going 5-...
2
votes
4answers
339 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 ...
6
votes
3answers
2k 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 ...
5
votes
5answers
2k 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: ...
1
vote
3answers
119 views

Random Phantom Sound On Computer - Could it be from ham radio?

For the past few months, I've been experiencing an odd random sound on my new computer (as well as 2 other PCs I've tested). It seems to occur only when the internet is connected. I have changed ISPs, ...
1
vote
1answer
123 views

Will very close proximity to electrical wires affect radio signals?

I'm planning to use a ESP8266 WiFi module with inbuilt antenna to test a concept. I plan to put it inside a wall mounted switch board/power outlet board. Will the electrical wires seriously affect ...
2
votes
3answers
1k views

What does it mean to have “RF in your signal”?

I've been told that I have "RF in my signal". What does this mean? What are some potential causes of having RF in the signal?
1
vote
1answer
91 views

Power supply for small radio board

I need a powersupply for a radio board (I will shield it), and have experienced bad interference from step-down converters. I have been told to use linear regulators (LM317 or LM350) with caps to trim ...