[Xastir] Off-topic: Rx eight freq. at once via RTL SDR: Send to Icecast

[John Wilson]

Thanks for the info Curt. I did buy one of those dongles and an going to
try the procedure for setting up my APRS radio for proper output according
to the instructions on the wiki.

I can see this info pertinent for future use as well.

73 John

On Jan 19, 2017 11:43 AM, "Curt Mills" <curt.we7u at gmail.com> wrote:

> This is off-topic for Xastir/APRS but figured some might be interested.
>
> I wanted to set up an RTL SDR dongle to receive our SAR frequency
> (high-band VHF, FM narrow) and send to an audio streaming server. I did it
> with a pipeline of commands on Linux. I mentioned it on another list:
> Another SAR guy two counties away (Hi Tom!) mentioned that he wanted the
> same thing but with multiple frequencies so he could choose which frequency
> to listen to.
>
> The idea is that SAR members and their family members could attach their
> portable devices to the stream and listen to live SAR traffic during the
> mission. For SAR members this is most useful on the way -to- a SAR mission:
> They can hear the recall code or perhaps more specific directions or
> important facts as they are coming in to the search area. All very useful
> if they don't own a SAR radio but have a cell-phone (and are in range of
> the cell network of course).
>
> So... Ken, N7IPB, and I redid the scheme and can now receive eight AM -or-
> FM frequencies at once per RTL SDR receiver, using one piece of software
> instead of a pipeline of commands. There are also free audio servers where
> you can send these streams so you don't have to run your own Icecast server
> either.
>
> I spent one day walking around the house with earbuds in and my cell-phone
> listening to a 220 repeater this way. I set up eight 220 frequencies on the
> RTL and could choose which audio stream to listen to. Since it was
> squelched most of the time and sending samples of zeroes, the cell-phone's
> battery didn't get depleted. Note: There is quite a delay with this method,
> in my case 20+ seconds from RF to when I hear it in the earbuds, but much
> of that is probably audio buffering in the client on my phone. I'm using
> VLC on the phone.
>
> One must patch the RTL_Airband code to send constant samples of zero when
> each channel is squelched to keep the audio channels streaming, but other
> than that it's pretty simple. 8 AM or 8 FM frequencies can be set up this
> way, anywhere between 24 MHz and 1.77 GHz, as long as all 8 are within the
> 2.4 MHz passband where you have the RTL tuned.
>
> If anyone wants to do the same I'm happy to share my configuration, minus
> the login/password for my Icecast server.
>
> Total investment: $25 for a TCXO RTL SDR dongle, and a whole bunch of time
> playing and testing until we figured out the magic formula.
>
> --
> Curt, WE7U
> http://we7u.wetnet.net
> http://www.sarguydigital.com
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