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Questions tagged [rfi]

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

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3 answers
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Will antenna insulation protect from RF burns?

Will antenna insulation protect from RF burns? I understand that antennas should normally be built with their insulation on. Will that insulation protect from RF burns? Up to what power level? If not:...
SRobertJames's user avatar
1 vote
2 answers
58 views

Will a LPF filter on the transmitter prevent CW key clicks?

Reading about key clicks, it would seem that they are primarily caused by the fact that the square wave of turning the key on and off must, by definition, have higher frequency harmonics, which sound ...
SRobertJames's user avatar
1 vote
2 answers
133 views

What is this pulsating signal?

When scanning through UHF, I find that there are a few frequencies that made a sound similar to a fast drum (~300 bpm?) Here are a list of the frequencies: 451.200 MHz 454.280 MHz more coming soon ...
o'o's user avatar
  • 513
3 votes
1 answer
54 views

Why does RFI demodulate to a buzz sound?

For RFI problems with audio equipment, why does a dead carrier often demodulate to the familiar mains 60 Hz buzz sound? This occurs on multiple audio equipment around the house. There are lots of ...
multicode's user avatar
1 vote
2 answers
137 views

Amateur radio antennas cause static on a cell phone call

My neighbor is a Class 8 truck driver and he recently put up what appears to be a large antenna outside of his house. I assume it is an antenna for radio - sorry, I am not technical and I just moved ...
Gretchen's user avatar
3 votes
0 answers
146 views

Strange interference - consistent series of beeps/chrips at frequencies 145-146 KHz apart

I'm new at Ham Radio, in fact still studying for Technician (so I can't transmit) but I purchased a used Icom IC-746, dipole antenna kit and most recently a Hexbeam antenna. The power supply is an ...
David Rouse's user avatar
2 votes
1 answer
116 views

A passive splitter/combiner in full-duplex mode

We have an RF chain where a full-duplex radio transceiver with Tx and Rx port operating on different frequencies. These are connected to a single antenna (that can Tx and Rx) via a diplexer, so that ...
ITried's user avatar
  • 123
1 vote
2 answers
200 views

Does a grounding block on a Yagi antenna with a balun and coax feed have the potential to add signal interference?

I have a commercial UHF/VHF Yagi designed for TV reception, also used for 2 meter reception, that has been installed for years but seems lately there's increasing amounts of signal disruption. I have ...
acker9's user avatar
  • 113
4 votes
2 answers
439 views

Coax in the wall, or around the house?

I am mounting a hex-beam antenna to the peak of my house (assuming that I can find someone with a cherry-picker or a scissor-lift that can help me get it up there). Right at that end of the house is ...
Don Levey's user avatar
3 votes
2 answers
303 views

Rfi in truck with HF transceiver when running

I have an Icom IC-707 in my truck, a 2003 F150, with a stainless 102 inch whip mag mount on the roof. It has a a coil pack 6 cylinder. Without it running I have no problem; as soon as I start the ...
Plumber90's user avatar
2 votes
0 answers
165 views

Receiving a lot of noise with RTL-SDR and SDR# for GOMX-1

Hi im new to SDR and having issues setting up SDR#. I'm trying to receive from GOMX-1 on 437.25 MHz for a project. My set up is the dongle, a LNA and a self built helical antenna for that frequency's ...
Rob's user avatar
  • 21
1 vote
3 answers
347 views

RFI makes 10m almost unusable

Seeing a lot of solid vertical lines on the spectrum scope of my ftdx10 and they’re really annoying. I have a yaesu fp1023a powering and ftdx10. Doesn’t go away if I turn off every circuit in the ...
Chris G.'s user avatar
  • 111
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
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
230 views

RFI every 24 kHz from 2.7 MHz to about 5 MHz

Quite recently, a significant noise source has shown up on my HF radio - it is NOT from my property as I have turned off the main breaker to the house - completely NO power - and still observe it on ...
Raydeeoh's user avatar
2 votes
5 answers
227 views

Garage Door Opener Damaged by HF RF?

Yeah, this is a crazy one. My wife's garage door opener stopped working yesterday. I replaced the battery and it works when very close to the garage door receiver, like underneath. Today, my son tells ...
user11702's user avatar
  • 111
1 vote
1 answer
63 views

Need help with RFI issue

I am running an IMax 2000 antenna with a President Lincoln 2 plus radio. I am having a lot of issues with ac noise coming through my antenna. I ruled out the noise coming from my home by turning off ...
Rockindcny's user avatar
2 votes
3 answers
895 views

Baofeng UV-5R: Severe static/interference on UHF frequencies

I have a U5-5R, which I've set up to use (among other things) the analog (NFM) frequencies of the PMR446-band. I've been using it with the stock (136-174/400-520MHz) antenna and a monophone connected ...
razumny's user avatar
  • 121
1 vote
0 answers
234 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
3 votes
1 answer
183 views

Easy Digi PTT circuit with Baofeng or Kenwood HT stays on after transmitting on VHF

I got my Easy Digi all wired up correctly, believe me, it took a while because of this issue. I've ruled out the FTDI controller I'm using because I can manually activate the optocoupler but supplying ...
Neal's user avatar
  • 31
-6 votes
1 answer
141 views

Ham radio as a weapon? [closed]

So I have a weird situation happening and I'm not sure how to go about this. I've been getting headaches and weird sensations throughout my body as well my ears are ringing. Are there directional ...
Lightningmike's user avatar
5 votes
2 answers
913 views

Eliminating RFI from raspberry pi

I am trying to eliminate RFI coming from a raspberry pi 4. The Rtlsdr(enclosed in a metal case) is directly plugged into the pi without any USB extension cable. The frequency of interest is at 1420....
radastro's user avatar
3 votes
2 answers
151 views

What safety procedures should be followed when developing and testing a high power amp?

I'm designing a 300W power amplifier using the MRF300AN from NXP targeting a center frequency of 146 MHz. Obviously I need to keep my fingers out of it and test into a dummy load, but generally ...
KJ7LNW's user avatar
  • 775
2 votes
1 answer
322 views

How do I choose between T37-2 vs T37-6 for this High-Pass Filter?

My RTL-SDR V3 is being overloaded by an AM broadcast so I'd like to build a high-pass filter to block the AM broadcast band. I thought I'd start simple and try making the one shown in Fig 3 of "...
Bezewy's user avatar
  • 153
0 votes
0 answers
35 views

Could my HF antenna cause problems to these other antennas on the roof? [duplicate]

I am planning to purchase a property soon in an apartment block on the top floor. I am very very keen to install a HF multiband Yagi antenna on the rooftop. I notice some small cell towers and a ...
Engineer999's user avatar
2 votes
1 answer
110 views

What would cause this RF noise pattern? (Hum with associated "flapping" and beeping)

In quite a lot of places below 7000kHz I see a repeated noise figure. A hum, then about 12kHz above it a "flapping" with beeping noise, and then about 50kHz from that whistling with three ...
QuantumMechanic's user avatar
2 votes
0 answers
55 views

Any good RF noise "libraries" out there?

Are there any good/useful "libraries" of RF noise out there? I know about http://www.arrl.org/sounds-of-rfi but it is pretty limited. (And I wish the screencaps showed the FFT rather than ...
QuantumMechanic's user avatar
3 votes
2 answers
1k views

Erratic behavior on Baofeng UV-5R Plus

I bought a UV-5R Plus (8 watt radio in the same casing as a normal Baofeng), and I've noticed some strange behaviors. Occasionally when I key up on my local repeater, the radio turns itself off and on ...
Proxy303's user avatar
  • 131
5 votes
2 answers
365 views

Will a HF beam antenna on rooftop building interfere with other antennas there

I am moving into an apartment on the top floor of a building and I intend to install a HF beam antenna for 20 to 10 meters, on the rooftop of the building. I notice that there are already some ...
Engineer999's user avatar
3 votes
1 answer
891 views

Transmitted audio coming out through my speaker

I have a Kenwood TS590 HF transceiver. When I am transmitting and speaking into the microphone, I can hear my audio slightly coming out of my speaker connected to the radio (SP-23), or headphones if ...
Engineer999'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
-4 votes
3 answers
317 views

Can ham radio antennas interfere with RING devices, causing them to produce high-pitched noise? [closed]

Can a HUGE ham radio antenna on a house with an array of RING devices (5 in total) cause interference and high-frequency reverberation? The attached shows one of these devices (there's 2 under the ...
Steve J's user avatar
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
0 votes
1 answer
126 views

What would cause 3 bursts of FM radio interference every ~3.5 seconds

I’m trying to locate the source of some interference on the FM band — it’s audible as 3 quick staccato bursts of brownish noise approximately every 3.5 seconds. It’s more pronounced at the low end of ...
Toadfish's user avatar
  • 131
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
0 votes
2 answers
106 views

Can a slinky serve as a ferrite core and if so, is there a prefered configuration? [closed]

Ferrite cores ain't cheap when you start talking about the 3 inch ID ones. I can see em for like 40 and 50 bucks.... I don't see why I can't just ground a slinky or something.
NonYaBidnezz's user avatar
1 vote
2 answers
476 views

In most Solar Systems what causes more QRM on HF ham bands, the panels, the charge controller, or the distribution system?

Looking at solar systems Hams mention that solar often brings RFI into the system, what part of the system in most likely to introduce RFI detectable on the ham bands?
hehe3301's user avatar
  • 157
8 votes
1 answer
166 views

S Parameters in HFSS

I'm new to HFSS Software and I'm trying to plot Scattering parameters for a dielectric resonator excited by a probe (shown in image). I know that the top cylinder has a higher dielectric than the ...
JOHN's user avatar
  • 81
2 votes
1 answer
299 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 ...
Edward Anderson's user avatar
3 votes
2 answers
305 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 ...
fiacobelli's user avatar
0 votes
2 answers
494 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 ...
K8KV's user avatar
  • 377
1 vote
1 answer
793 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 ...
Philip Lee's user avatar
1 vote
2 answers
176 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 ...
rclocher3's user avatar
  • 9,242
2 votes
1 answer
261 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 ...
hairlesshobo's user avatar
1 vote
1 answer
92 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 ...
mtpc1486's user avatar
3 votes
2 answers
499 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 ...
Kenn Sebesta's user avatar
4 votes
0 answers
121 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 ...
Jeremy Gilbert's user avatar
2 votes
1 answer
254 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,...
TEQATAR's user avatar
  • 43
6 votes
2 answers
110 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 ...
YellowBadger's user avatar
2 votes
1 answer
124 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....
t252's user avatar
  • 697