[NovemberWhiskey]

>How did this thing get FCC approval?

Looking at the radio display, it seems like the peak power is about 7-8 S-units. At VHF, that would be about -100dBm; or about 100 femto-watts. I presume that the charger is pretty near the radio. With free-space path loss being inverse square law, it's essentially going to be completely negligible within a very short distance.

Oh, and if the antenna is indeed near the charger (say within one wavelength, 2 meters in this case) it might be inside the near-field - which means that you're getting additional power transferred that wouldn't be reaching the far-field, and you might even be affecting the behavior of the device due to coupling.

Looking at the FCC report, the radiated emissions are totally in-line with FCC Class B requirements.

Modern ham radio equipment has exquisitely sensitive receivers and you easily hear all kinds of interference from digital devices that are completely Part 15 compliant. The prevalence of switched mode power supplies literally everywhere has made HF radio completely unusable for many people outside rural areas.

[amatecha]

I use HF radio all the time from inside my home, in the middle of one of the densest cities in BC. Within the past few weeks I've made contacts with stations in Alaska, Belize, Costa Rica, Colombia, Russia and Japan with a radio inside my home in Vancouver, Canada. HF is 10000% usable in urban areas. It's not optimal or perfect, but it's just fine.

[jrockway]

Making the contact is easy (the interference you hear doesn't exist at the receiver), hearing the other end is hard. Most of my indoor QSOs are people running 1500W FT8 which is ... an unnecessary amount of power. (Meanwhile, I'm sitting here transmitting at 3W.)

I often look at the automated reports and look sadly at the 99% of stations that can hear me but that I can't hear.

[amatecha]

Yup, RX harder than TX in the city, that's for sure. I'm thinking to set up a "loop-on-ground" antenna[0] for RX which, from anecdotes I've heard from people I know, takes their S8 noise floor to like S1.

[0] http://www.kk5jy.net/LoG/

[jrockway]

I should definitely set something like that up. I have a patio now and this would be unlikely to annoy anyone above me looking at my patio and reporting it to the board. (Not that I think my neighbors would care, but it's a common complaint against hams.)

[NovemberWhiskey]

Sure. Right now, we're coming towards the top of a sunspot cycle that results in SFI levels not seen in 20 years. Let me know how you were doing in 2019. There's obviously a seasonal overlay here.

[amatecha]

I wasn't an op in 2019 -- got my certification in 2022. That said, I used to receive FT8 with my RTL-SDR and have a few screenshots. Here's a map of my received signals on 40m, overnight in May 2020, with a random-wire antenna: https://i.imgur.com/flfyIZx.png At that time I lived in an even more densely-populated area (a condo complex with over 100 units, on a main street, surrounded by other similarly-large condo complexes).

[jrockway]

Oh man, I haven't been paying attention to the sunspot cycle. I got my license at a low and committed to being depressed about it forever, but ... time fixes everything I guess!

[threeio]

its still doable in 2019... just not as plentiful ;) I was still able to get DXCC during the lows in a Silicon Valley downtown tiny lot (however, this isn't an apartment in a major city)

[asdefghyk]

Would not a persons specific setup have significant effect on the interference situation, - The radio would be in a completely shielded metal box? - so no interference that way directly , not via the antenna input. Outside antenna , with a shielded feed in cable would also reduce interference from these devices like small power supplies that just produce interfearance to a few meters distance ???

[kaishiro]

As someone who has always been interested in getting into ham radio - do you have any pointers on where to start or what to avoid?

[MandieD]

First of all, get your entry-level license. If you're in the US (or have someone who can receive mail for you), this is relatively easy and inexpensive, and can be done completely online.

Avoid sinking a lot of money into a transceiver immediately before you've been operating for awhile and know what you're really interested in doing. You also do not need a rooftop antenna for HF (3-30 MHz; the frequencies that most often travel far) - a wire across your backyard can be quite effective.

Since you're here, I recommend getting started with digital modes like WSPR and FT8. They require a lot less power to make some surprising connections, and will teach you a lot about how propagation works and adjusting antennas, and because of the low power requirements, can be done with relatively inexpensive equipment. Some "old timers" grouch about how they're not "real" ham radio, but ignore them.

Edited to add: A good starting point that doesn't even require a license is to get an SDR receiver like the RTL-SDR and hook a long wire to it as an antenna, then listen for WSPR or FT8 signals with WSJT-X, and whatever else (other digital modes, Morse Code) with fldigi.

[matthews2]

Join a local club!

[t0mas88]

Near-field being as big as 2 meters from the charger can be quite relevant for use in aircraft. Since on a narrow-body aircraft passengers can easily be within 2 meters of some of the VHF antennae.

On the other hand, aviation voice radios aren't very sensitive and navigation radios have filtering built-in. So the output of an Apple charger is probably some orders of magnitude too small to cause any issues.

[jrockway]

> Since on a narrow-body aircraft passengers can easily be within 2 meters of some of the VHF antennae.

But, separated by a very large piece of conductive metal. (I think even carbon fiber planes have a conductive layer in there, to prevent damage from lightning strikes.)

[skykooler]

Isn’t carbon fiber conductive itself?

[thenickdude]

Yes, and blocks radio transmissions very nicely. When making a model airplane with a carbon fibre hull, we have to add a plain fibreglass or plastic window for the antenna to receive through.

[tonyarkles]

Carbon fibre is definitely conductive. A couple of years ago I measured a 1” diameter tube and got about 15ohms/ft.

[Animats]

Right, it's a resistor. This is a problem for airframes and wind turbine blades. Its resistance is too high to deal well with lightning. So aluminum is needed to provide a conductive path.

[crote]

Do you have any idea how that power compares to regular FM radio broadcasts, which are somewhat close in frequency?

Is this something a regular radio would detect, or is OP just trying to listen to a handheld radio half a continent away using a really sensitive receiver with the volume knob turned all the way up?

[amatecha]

Due to proximity, the interference from the charger is comparable to what the receiver was expecting from a normal signal (like an amateur radio repeater or fellow operator's station), which is why his radio broke squelch while scanning. Because the radio is relatively close to the charger, the RFI is picked up quite well.

Comparing to a broadcast FM station, the strength of the RFI as observed by any nearby radio will be trivial by comparison. Broadcast stations are some of the highest-power radio transmissions around us, typically thousands of kilowatts (for example the rock station near me transmits at an ERP of 51,000 watts[0]). You will hear this station clearly no matter what kind of nearby RFI is present, and the receiver's AGC will reduce RF gain to probably as low as it goes. By comparison, amateur radios typically operate in the range of 5-100 watts. Thus you might gather that comparing localized RFI to broadcast stations is not a meaningful comparison.

[0]https://en.wikipedia.org/wiki/CFOX-FM

[FireBeyond]

> Broadcast stations are some of the highest-power radio transmissions around us, typically thousands of kilowatts (for example the rock station near me transmits at an ERP of 51,000 watts[0]).

I don't think so.

Not "thousands of killowatts" transmitted. Your example is as you say, an ERP of 51kW.

But even ERP doesn't refer to the transmitter. An ERP of 51,000W is most likely a 5-10kW transmitter, with a gain factor of 5-10.

[TylerE]

Back in the pirate radio days 100 and 250kw transmitters were common.

Back in the '30s a few AM stations ran at 500kw, and could be picked up on other continents.

[FireBeyond]

AM? Definitely, but even that is 100, 250, 500. Not "thousands of kW".

[amatecha]

Oh sorry, I doubled up my units of measurement there, yes, tens of kilowatts haha :) (unfortunately too late to be able to edit that comment)

[NovemberWhiskey]

To get a very broad idea: if you had perfectly efficient but isotropic antennas (you don't) this would be about the power level you'd get receiving a typical 3W hand-held radio signal at 140MHz from 1,000 kilometers away. This is why you can talk to the International Space Station easily enough with vanilla ham radio equipment.

Or, taking a notoriously powerful FM radio station like KRUZ 103.3, it would be like hearing that station from perhaps 300,000 kilometers away.

Most loss is not free-space loss though - it's due to reflections from man made objects and absorption into the earth that results in line-of-sight effects at these frequencies.

[amatecha]

How did you come to that estimation? The strength of the RFI on the waterfall suggests received signal strength comparable to someone transmitting on a 5w HT within, say, 5-10 miles (aka not in the immediate neighbourhood, but pretty nearby). Someone transmitting 3w at 1000km distance will not register even the slightest on any amateur receiver, even with RF gain absolutely cranked to the max and with a massive antenna.

[NovemberWhiskey]

I actually updated my post about the same time you wrote this response; I was just considering free-space path loss, which is not where most of the loss is in typical ham scenarios. Most of the 5W in the case you described is getting lost in a terrible compromise antenna, then due to line of sight effects (assuming that the user is not standing on a hill or something) and multipath.

[TylerE]

The ISS also orbits quite low. If you're relatively close to the path it's only a few hundred miles away. Small temporal window due to the speed, but still.