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

-2
votes
0answers
15 views

steady rf noise from s7 to 20 over

i have a mfj 1798 vertical. i've had it for several years now and it's been good for being mounted o the roof.when i first installed it it did exactly as the instructions said as far as swr starting ...
2
votes
4answers
257 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?
4
votes
1answer
152 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
93 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 ...
2
votes
1answer
93 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 ...
2
votes
3answers
88 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
30 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
50 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 ...
4
votes
2answers
158 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 ...
0
votes
1answer
48 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
128 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 ...
3
votes
2answers
66 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
167 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 ...
6
votes
3answers
177 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 ...
2
votes
2answers
125 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.
4
votes
3answers
133 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
139 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 ...
3
votes
3answers
656 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
726 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
107 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
102 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
421 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
72 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 ...
2
votes
2answers
93 views

Filtering VHF FM on my DTV signal

I've noticed that when I transmit on my HT when I'm watching TV (OTA), the signal drops and the screen goes blank (or digital "static") and then returns when I stop. I've replicated the issue by ...
5
votes
2answers
433 views

What is the purpose of limiting radio output power?

According to article 25, section I, § 4 (25.7) ITU's Radio Regulations: The maximum power of amateur stations shall be fixed by the administrations concerned. In my country this is 500W for CEPT ...
7
votes
1answer
203 views

Super-low-tech VHF low-pass filter construction?

Related to this question: Is it legal to broadcast an FM radio signal with a Raspberry Pi Zero? Is it possible to build a super-low-tech low-pass filter for VHF harmonic suppression without a PCB or ...
2
votes
2answers
104 views

Laptop screen goes blank when transmitting from handheld within a few feet - sometimes

I noticed that when I transmit from my handheld Baofeng Radio, with the standard rubber duck antenna, that my laptop screen goes blank. This only occurs if I'm within a few feet, and even on powers ...
1
vote
3answers
138 views

How can I scan for interference [closed]

What app or software can I use on my windows 10 computer(desktop) or iPhone 7 latest software to scan for interference as in another device effecting my frequencie of my Bluetooth wifi in a 2.4 and 5 ...
1
vote
2answers
80 views

different digital modulations interference. Does it happen?

Bottom line is I have got a very strange (but regular) reading on a < $1 type of ASK 433 MHz receiver. Have a look at it - those 3 spikes are sometimes caught by my receiver, don't know their ...
1
vote
1answer
122 views

Using coax for DC, good idea?

I know that it is best to twist the wires that supply DC power to a device, as to decrease the "loop" surface area. This diminishes the amount of RF that gets coupled in the wires as well as the ...
27
votes
13answers
14k 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 ...
8
votes
4answers
271 views

How to operate on HF if an AM transmitter is only 540 feet away?

I'm a General Class Licensee, and due to pulmonary disease I cannot operate voice. I am also about 540 feet from a 24/7 1 kW AM station. The signal is so pronounced that most audio devices in the ...
6
votes
1answer
188 views

How can I counter DC-DC inverter noise / ground noise in an electric-vehicle mobile setup?

So, I'm relatively new to all this; and I've gotten an ICOM IC-7100 on sale, which looks like an excellent transceiver … unfortunately, this very specific line shows up in the manual: The ...
0
votes
1answer
62 views

How does inductive coupling between transmitter amplifier stages reduce harmonics

In some notes on transmitters I have found the statement that "inductive coupling between transmitter amplifier stages reduces the generation of harmonics", with no further explanation. Can anyone ...
2
votes
3answers
225 views

Can you jam jam?

Is it possible to jam the jammer signal, to disrupt its jamming of the owned RF signal?
2
votes
4answers
147 views

Measuring a device's 2.4 GHz RF signal in an open field/indoors

How can I measure/what instrument should I use to identify/measure the RF signal strength in a "noisy" environment? For example, I want to measure the RF signal strength of my device at a particular ...
3
votes
1answer
186 views

What might this “spreading” interference be?

Any idea what might be causing this signal to appear in the "panadapter" spectrogram of my Omnia SDR around the 40m band? Every twenty seconds, I get a strong "focused" signal that then rapidly ...
0
votes
2answers
97 views

How can I find out if a particular LED light bulb model is known to cause RFI before buying?

With «green» electricity bills amounting to ever more greenbacks, I am in the process of gradually replacing my incandescent light bulbs with LED light bulbs. However, my efforts met with mixed ...
3
votes
2answers
1k views

Understanding coax radiation and “current on the shield”

I'm having trouble understanding what seems to be the fundamental principle behind baluns (and probably other related topics). Perhaps some of my confusion comes from an audio background, where one ...
1
vote
1answer
93 views

Transmitter won't transmit with antenna installed

I built a node for my friend out of a baofeng BF-888s UHF transceiver. I am powering the radio with a voltage regulator, and a few caps with a wall wart power supply. The radio will transmit fine ...
3
votes
3answers
1k views

How to stop interference on shortwave radio when connecting to a computer

I have a Tecsun PL-600 and when I can receive clear signals, and they come through just fine on headphones, and through the speaker. If I'm trying to receive RTTY or fax, when I connect the radio to ...
5
votes
3answers
727 views

Noise & shielding, SDR Dongle

First, I'm very new to SDR. This may turn out to be really obvious. I just want to verify my thoughts before I spend more dollars. I have a USB dongle with the RT28xx in it. Works great. Side by ...
3
votes
3answers
944 views

Why did I lose my FM radio signal?

My lady and I were driving on the interstate recently when we noticed an unusual phenomenon. We were listening to the radio (an FM signal), and only over a couple of bridges did we entirely lose our ...
1
vote
2answers
304 views

Inverter noise on my signal

I recently built a sound card packet TNC and it is working fine under my standard laptop power supply when I hook it into the wall. When I plug my computer in via a car inverter (12VDC to 120VAC), ...
2
votes
1answer
133 views

Computer cables in shack — what to do with them?

What should I do with all the cables connecting this to that? Coiled, folded, cut-to-length, wound on ferrite? Anyone have the definitive answer to this? My rat's nest is getting more messy. The ...
3
votes
1answer
435 views

Cellular VHF Interference

I just got my license a week ago. Installed a new VHF/UHF radio in my car and everything seems to be working great. I've been heard at distant locations and picked up signals from repeaters that are ...
2
votes
1answer
254 views

Low frequency noise on ground line. Why?

I'm currently experiencing what I think is induced coupling on my ground line. Can someone explain how this is possible? I live on the third floor of an apartment block and my only grounding option ...
4
votes
1answer
118 views

OK for S/RF light to be illuminated at engine idle?

I just installed a mobile CB (Uniden) into my Jeep. When the key is in auxiliary (car off, accessories on) and the squelch turned all the way down, no S/RF lights are illuminated and the background ...
4
votes
2answers
398 views

How to choose right inductors for a matching circuit

I would like to chose an inductor to make a matching circuit. Operating frequency is 6.1 GHz. I am more concerned with self resonance frequency and Q of an inductor. Would an inductor with SRF > 7 ...
3
votes
4answers
8k views

Advantages of using Digital Code Squelch

I am trying to decide whether or not I should use a CTCSS (Continuous Tone-Coded Squelch System) or a DCS (Digital Coded Squelch) for my mini repeater I just set up. What are the advantages of using ...