[TangerineSDR] Good progress with KA9Q and Gnuradio

[Tom McDermott]

I would like to say thank you to Franco, K4VZ and Phil, KA9Q for lots of
great help this last week.

I have been successful in getting a Raspberry PI 3B+ with an RTLSDR dongle
working to send IQ data to Gnuradio
on a separate Linux host using the updated version of ka9q-radio.

1. When the host is run on a different computer than the radio is on (i.e.
over a network) then
one needs to add   ttl = 1  to the .conf file (ttl means time-to-live for
the packet)  Without the ttl parameter
it defaults to ttl = 0 such that the Raspberry Pi never sends multicast
data or multicast control over the
network connection (just to the RPi's loopback address).  My network has
IGMP snooping turned on so
that multicast packets are only sent on network ports with active
subscribers).  The multicast names
are properly resolving to IPv4 across the network.

2. There were some buffer problems that resulted in long runs of
zero-valued samples interspersed within
the IQ data. I had them all the time with my setup, Franco had them
intermittently with his.   This is working now on
my setup after pulling the Aug 24 update from the ka9q-radio github.

3. Franco's Gnuradio module seems to be working great without issues on my
setup (Ubuntu 22.04 / gnuradio 3.10).
It receives the IQ stream from the RTLSDR over the network and can tune the
output and demodule
NWS weather stations within gnuradio producing audio output. It shuts down
properly.

4. Phil's control program is now working (due to fix #1 above).

5. This has been tested so far at 48000 samples/sec so far.  The Raspberry
Pi 3B+ is running about 30% load
when sending this one multicast stream.

6. There are further tests planned (sample rate, RX888, etc.).


Again many thanks to Franco and Phil !  I know they spent a lot of time on
this over the week.

-- Tom, N5EG
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