HFU HF Underground
Technical Topics => Part 15 AM and FM Station Operation => Topic started by: ThaDood on September 13, 2026, 1817 UTC
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https://www.tecsun-radios.com/product/db30-hifi-headphone-amp/ My big gripe about using something as a Bluetooth possible Studio-To-Transmitter-Link to get some good quality audio to that site, which is range limitation, could be this Tecsun Headphones Amp, with fixed RCA Audio Outputs. Whatīs no known is what the actual range is. So, a link like +50ft away probably wouldnīt work, but if trying to link to a room, or two, close-by, where wired link just isnīt plausible, this might come in handy. Anyone ever try one?
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I don't know much about mesh networks except that they've become quite common place as a customer product. Maybe using mesh technology might be something to look into.
But for room-to-room situations, like around the house, yeah sure, Bluetooth is used for such all the time ain't it?
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I've used Bluetooth (BT) modules for short distance links, 20 ft or less, quite successfully. I have a audio processor which takes a stereo feed and processes it for an AM transmitter. I added a cheap BT receiver module from Amazon, less than $5, just provided 5v and tapped the audio output across the 3.5mm audio input socket so that without a line input the BT was connected and it automatically disconnects when you insert a plug. Simples.
As for mesh networks, I've not seen any wide-area implementations that would be suitable. Latency would be a problem and, as the route can change all the time, connections are not guaranteed. Bandwidth is also quite limited, even for audio. I'll stick to copper wire or BT.
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I'm not sure why the consideration of using the Tescun device would be necessary for a STL unless your feed is tape decks and turntables. But if using a computer you already have a built-in Bluetooth transmitter (good for 30 feet or so, no better (I'm presuming) than what that Tescun can achieve (again presuming).
I've not ever used one of those home mesh networks, but the 5G models wouldn't have any issue with latency. It's my understanding that those home mesh networks maintain reliable connections provided the receivers stay put and don't get moved around.
I'm not trying to push a mesh network, just saying it could work, but I suppose it's not a cheap option either.
I had experimented years ago for awhile using a Ruko box with a shoutcast stream, the intention was for a long-range STL, it actually worked alright. You can pick up an old Ruko for like $5 and even the earliest of versions should still work with a shoutcast stream. https://part15lab.blogspot.com/2014/04/roku-poor-mans-barix.html
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Apologies, I wasn't thinking about mesh wifi or even 5G, those are established consumer products but are expensive to setup just to use as an STL and you'd need a computer or some other device to be the 'end point'.
I was thinking of low-cost wide-area mesh devices like meshtastic which are great for text messages and maybe short bursts of data, but certainly not an audio stream.
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Ever since TheDood mentioned it, it keeps popping back into my mind and I got to thinking about hr drive-ins and recall some of them provided audio via an app. That got me to looking around. I've not researched any of this or anything, just poking around, but generally, part 15 Wi-Fi broadcast are limited to 1 watt power - that provides a potential of broadcasting a stable Wi-Fi signal up to a mile or more. Some Drive-In theaters use this method today, the largest of which is the Ford Wyoming Drive-In in Michigan and the smallest at the Blue Starlite Mini Urban Drive-In in Texas. Holiday Twin Drive-In in Colorado also does it this way, as does 'Cinewave' pop-up theater setups too (https://www.cinewav.com/audio-solution-for-drive-ins). True, most drive-ins use FM now, it's considered "the gold standard" but there's at least one still provideds both AM and FM... But the point is that several of them broadcast the movie audio directly to smartphones (and/or the car 'smart-radio') app - no internet involved, it's simply an OTA part 15 wifi signal. And it's not just drive-ins, it's football stadiums, amusement parks and other outdoor gatherings.
Anyway, Part 15 Wi-Fi broadcasting for a mile or more, sounds intriguing doesn't it? Anyone with a smartphone in range could listen to your OTA wifi stream, no signing up, no login, the listener simply clicks on the wifi connection just like you would any Wi-Fi showing up on your phone! So simple.
However, it's still a two-way communication same as any other wifi, the phone has to send data packets back - It's all an automatic process, the user does nothing, bu the smartphone wifi communications are what's limited - not by rule, but by it's battery power limits it to about 100mw of broadcast power, good for around 300 to 700 feet range outdoors based on surroundings and considerably less if indoors. So how is it the drive-ins and sports stadiums address this issue?
Distributed network is most common, essentially little repeaters spread out throughout the area so there's always one close enough where a phones can communicate data back.. I guess it's a kind of mesh network. There's also a method conceptualized using a single transmitter installed atop the projection screen with some kind of high gain receiving unit and antenna capable of pickup the phones a greater distance, but apparently no one has actually implemented it. There's even a way to accomplish it where the phone doesn't have to communicate back at all (thus not being limited by the phones broadcasting power) and any smartphone could listen, no latency whatsoever, but it a person walking by could cause dropouts, and somehow it rapidly drains the batteries of the phones that connect to it.. or something like that.. it just has more pros than cons.
So, bottom line, use of wifi standard TCP is most common method (Transfer Communication Protocol - I think).
For a hobby wifi station the TP-Link Omada EAP225-Outdoor (around $100) or the Ubiquiti UniFi U7 Pro Outdoor ($250 or more) is a complete, all-in-one. Transmitter/receiver/antenna entirely inside a single weatherproof unit. That's pretty cool, but I got to wondering what the smallest drive-in I mentioned earlier that holds only 40 cars uses as a transmitter, I figured small venue, small budget, right? Apparently they use 'Audio Fetch', apparently a company that installs such systems: https://www.audiofetch.com/venues/drive-in-audio/ - I tell you what, it looks like a portable router that cost $650, I'm just saying it don't look like there's much to it.