can Gqrx do audio streaming between ham stations and manage GPIO pin?

[EA2DXT]

Hello all , I have a crazy question

I have knowledge on electronic design but I am novice on linux and this kind of programmable embeded systems.

Some years ago I tried to make a PCB design for a repeater controller, but It needs a lot of work and it was not easy upgradeable.

This new re-programmable devices, raspberry or similar, and low cost SDR receivers add new oportunities for HAM users or others... ;-)

Can this package manage audio streaming from/to another Gqrx station ?

Can it be installed on a RaspBP Zero ?

Can Gqrx add CTCSS decode functions as squelch ON/OFF or GPIO manage?

The basic scenario I am thinking is something like...

Analog HAM repeater located on a remote station

and 2 SDR receivers conected to a RBP Zero on different location

a WIFI link between them    (now we have that link running with 2 Ubiquiti stations for other purposes)

Can I boot Gqrx with a predefined setting like frec 145.000, N-FM and send audio streaming to analog station via wifi link ?

(in case of reboot from a power down or reset)

Obvious, on analog station I need another device to download stream audio to analog and control PTT

I am looking to make a remote receiver to our local repeater because of high local RF noise

the 2 remote SDR is to receive 2 fixed frecuencies VHF and UHF  (maybe changed on future or eventually via remote tcpip connection)

 (example, stream audio in stereo mode , VHF audio on left channel and UHF on right , or something like that) 

A low cost and low power remote system.

I hope you understand my question.

ThanU in advance.

[Alexandru Csete]

Hello EA2DXT,

You can use gqrx to receive one channel and stream audio to a remote
client over UDP or audio piping. But it is a graphical application and
needs a monitor and a rather strong computer - at least a raspberry pi
2 or 3. It will not work on the raspberry pi 0.

Alex

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[EA2DXT]

Hi Alex.

mmmmm..... OK

Even if the application needs a very small RF spectrum sweep?

The idea is to select the smallest sweep on each SDR dongle, for example 250Khz  (HDSDR can do that on Win version via RTL dongle) and a small portion of 10-15khz for FM audio decode

The graphical can be set to slowest refresh rate because no local monitor, all of them to compensate compute power to make an UDP traffic.

Maybe in this situation compute power will be as low to use a "basic" RBP device, if not obviouly we will try with a better RBP.

But the scenario can be done and add small "plugins" for CTCSS or control some GPIOs ??

Thanks Alex for your answer.

[Robin Gape]

¡Hola!,

a much simpler alternative approach if using RTL dongles would be to use rtl_fm as the receiver, since one presumably needs a receiver on a single frequency. Then for all that troublesome (complex) repeater logic, including CTCSS, one could try SvxLink http://svxlink.org/. Alternatively, if using different RF front ends, GNU Radio comes with GRC, which allows one to build an SDR signal processing chain from graphical blocks.

Um, and whilst we're at it, in terms of dinero, the cost of setting up the remote receivers in terms of mechanical structures, civil engineering, backhaul, volunteer time & effort, &c. far outweighs the cost of the computers. There may be issues with power to run the remote stations, but the RTL dongles, or most other RF front ends, will take appreciable power.

Depending on the local RF environment, you may need some serious RF filtering to keep other signals out of the dongles. 8 bits gives a maximum RF dynamic range of around 48dB (depending on a number of factors). After all that effort, you don't want the remote station to go deaf every time an aircraft transmits, the emergency services are called, a boat comes in to Bilbao, or there's a sporadic-E opening on 2m!

One could breadboard such a system with desktop/laptop PCs, but it's most definitely not a weekend project!

Good luck, 73,

Robin, G8DQX

[EA2DXT]

ThankU Robin

Mechanical structures and civil is now running, the only cost of work will be as volunteer time :-D  people of our RadioClub will help us to make a better HAM repeater.

In terms of RF filtering, now we have a couple of RF cavities to filter unwanted RF "noise" 

Some days ago I found another interesting modules DRA818

It is a simple VHF and/or UHF radio on a compact size, probably you know them.

It is not a real SDR with its PRO and CONs but maybe will do the job that I am thinking.

Now the only reason to use RaspBerry is to make a wifi bridge between two of them just to "transport" digitized audio with some extra signaling from/to main repeater.

One DRA818V (VHF version) and DRA818U (UHF version) , both as receivers, and for example as stereo system , VHF left channel / UHF right channel or something like that.

 

Probably this option is not for a Gqrx SDR project and I need to make the question on a RBP forum.

Maybe the use of GNU Radio will help 

Thanks.

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