61–70 of 89 posts
Earlier quoted context omitted.
They do that with very carefully optimised equipment.
And when certain atmospheric conditions exist.
No need for "certain atmospheric conditions".
The point was that very low power signals can go a long, long way.
If you want to build fully legal applications that transmit FM you can use the Si4713. https://learn.adafruit.com/adafruit-si4713-fm-radio-transmit... John Park did a short video on it https://www.youtube.com/watch?v=PKP6Z-cEbFQ You can also buy a fully legal MP3 FM transmitter. https://radiofidelity.com/best-fm-transmitter-for-your-car/ Bitluni made a fun (illegal) AM radio transmitter with an esp32 https://youtu.be…
You set the sound card output at your OS settings and everything it's broadcasted over FM.
I know some of them exist for bluetooth audio, but not for FM.
If you want to build fully legal applications that transmit FM you can use the Si4713. https://learn.adafruit.com/adafruit-si4713-fm-radio-transmit... John Park did a short video on it https://www.youtube.com/watch?v=PKP6Z-cEbFQ You can also buy a fully legal MP3 FM transmitter. https://radiofidelity.com/best-fm-transmitter-for-your-car/ Bitluni made a fun (illegal) AM radio transmitter with an esp32 https://youtu.be…
I would like an USB FM transmitter which shows up as an USB audio card. You set the sound card output at your OS settings and everything it's broadcasted over FM. I know some of them exist for bluetooth audio, but not for FM.
- a USB sound card with 3.5mm jack, and
- an FM transmitter module (which can usually be powered with 3v-12v, so should be able to work with 5v USB power
Earlier quoted context omitted.
It has nothing to do with Motoroa, TDMA, or 5G. If the wanted signal is very weak (eg from a distant aircraft using VHF AM), and there is an interfering signal on the same channel, the emergency communications will be distrupted.
Aircraft using the VHF band with amplitude modulation is going to perform much differently than a police repeater and it's local upstream only amplifiers interacting with low wattage fixed handhelds and medium wattage car mounted mobile radios. Pivoting topics is a bad faith conversational tactic FYI, and doesn't follow HN's guidelines. I encourage you to fully read the guidelines linked at the bottom of the page.
TDMA amplifiers could well be a problem in your country, but the whole point of the discussion is that transmitting a wide band of RF hash will certainly be detrimental to thousands of other radio users, whether or not they are using a TDMA public network.
If you want to build fully legal applications that transmit FM you can use the Si4713. https://learn.adafruit.com/adafruit-si4713-fm-radio-transmit... John Park did a short video on it https://www.youtube.com/watch?v=PKP6Z-cEbFQ You can also buy a fully legal MP3 FM transmitter. https://radiofidelity.com/best-fm-transmitter-for-your-car/ Bitluni made a fun (illegal) AM radio transmitter with an esp32 https://youtu.be…
It provides a good signal, is easy to adjust, and works well for phone calls (not just music).
If you want to build fully legal applications that transmit FM you can use the Si4713. https://learn.adafruit.com/adafruit-si4713-fm-radio-transmit... John Park did a short video on it https://www.youtube.com/watch?v=PKP6Z-cEbFQ You can also buy a fully legal MP3 FM transmitter. https://radiofidelity.com/best-fm-transmitter-for-your-car/ Bitluni made a fun (illegal) AM radio transmitter with an esp32 https://youtu.be…
So you can get radio when there is no cell or data service - like when camping or hiking etc.
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In my small town, local TV reception was being completely wiped out by interference. When the Radio Inspector came to check, he found a rechargeable torch sitting in it's charger bracket, which generated horrendous interference whenever the batteries reached full.
I know the reverse of your story. And OLD TV from a grandma jamming an entire town: https://www.popularmechanics.com/science/a34229436/old-tv-br...
And there's a twist to this: ADSL data networks attempt to feed broadband signals over unshielded (and poorly balanced) phone lines, which means that they are intolerant of legitimate radio emissions from licensed services nearby.
The ADSL system attempts to compensate for conventional transmissions by dropping out those channels, but any wideband impulse causes the entire system to hang while it unsuccessfully tries to find a clear set of channels. So each pulse locks up the system for a few minutes while it renegotiates.
A variation on this is the ignition on the Postman's motor bike which wipes out all the ADSL in each street that he visits.
The bottom line of course is that ADSL was a horrible hack which attempts (and fails) to bypass the laws of physics.
Earlier quoted context omitted.
Aircraft using the VHF band with amplitude modulation is going to perform much differently than a police repeater and it's local upstream only amplifiers interacting with low wattage fixed handhelds and medium wattage car mounted mobile radios. Pivoting topics is a bad faith conversational tactic FYI, and doesn't follow HN's guidelines. I encourage you to fully read the guidelines linked at the bottom of the page.
Nevertheless, the threat is to public safety communications. And not all Public safety use TDMA (or whatever). Aircraft communications is probably the most vulnerable, but so are HF/VHF marine operations, military and a host of others. TDMA amplifiers could well be a problem in your country, but the whole point of the discussion is that transmitting a wide band of RF hash will certainly be detrimental to thousands of…
Aviation needs to modernize, I have zero sympathy for the aviation community getting constant hallpasses on ancient altimeters that lack filters to reject RF from nearby frequencies, leaded avgas, and abysmal working conditions for those stuck in the industry.
The FAA dragging their feet in the USA trying to act like they should never have to test how interference affects hardware on planes is insane, they waited till well past when 3.5Ghz went into cellular use to make any effort to performance test altimeters for band conformance. The FCC's timelines are long, the FAA had at least half a decade heads up of when the 3.5Ghz auction would occur, and additional time after the auction before Verizon and AT&T put the spectrum into service.
We have waited 25 years past when everyone else stopped using leaded gas to get rid of leaded Avgas[1].
As a Seattleite who grew up with families made up of Boeing Engineers, the problem of vulnerable radio transmissions from aircraft could be resolved with a network of reception sites just like Gogo uses at a much higher frequency allocation. This problem is just not a priority for the Aviation community, they would rather not invest in better equipment and infrastructure.
1 - https://qz.com/leaded-aviation-fuel-is-prompting-bipartisan-...
Edit: Trunked, not Truned
Earlier quoted context omitted.
And when certain atmospheric conditions exist.
Except this discussion is about possible interference across town, or even more locally. No need for "certain atmospheric conditions". The point was that very low power signals can go a long, long way.
> And even a few micro-watts is sufficient to communicate across town.
> Many years ago the record was "1000 miles per milliwatt" using CW.
Earlier quoted context omitted.
Except this discussion is about possible interference across town, or even more locally. No need for "certain atmospheric conditions". The point was that very low power signals can go a long, long way.
You explicitly brought up long distance communication in this thread: > And even a few micro-watts is sufficient to communicate across town. > Many years ago the record was "1000 miles per milliwatt" using CW.