5 ms·

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 det

• NovemberWhiskey 3y ago
  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 3y ago
    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 3y ago
      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 3y ago
    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.
• amatecha 3y ago
  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 https://en.wikipedia.org/wiki/CFOX-FM
  • FireBeyond 3y ago
    > 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 3y ago
      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 3y ago
        AM? Definitely, but even that is 100, 250, 500. Not "thousands of kW".
    • amatecha 3y ago