Hello list,
First of all, thanks for the great tool.
I am a newbie, just started to play with gnuradio.
For the start, I’d like to implement some simple, low bit rate
modem.
I don’t have any particular hardware, so I’d use the sound card of my
computer, and hook up my HF radio.
So for the start I thought I download a PSK31 modem, but I couldn’t find
one. I am 100% sure that this has been done before. Could you please
give me
pointers to such projects?
The final project would be a GMSK receiver of telemetry data from a high
altitude balloon.
Thank you very much for your help.
73 de HA5OGL
–
Levente Kovacs
CTO, CSO
I have not seen a whole PSK31 modem implemented.
Looks like there is a decoder here:
and here:
I experimented with an encoder here:
It would be allot more work writing the GUI front end than the actual GR
portion of the modem; probably why it has not been done.
Thanks,
Lou
KD4HSO
Levente Kovacs wrote
I don’t have any particular hardware, so I’d use the sound card of my
Thank you very much for your help.
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On Sun, 31 Aug 2014 10:13:08 -0700 (PDT)
madengr [email protected] wrote:
I have not seen a whole PSK31 modem implemented.
Looks like there is a decoder here:
GitHub - bitglue/gr-psk31: GNU Radio blocks for PSK31 groking
and here:
GNURadio PSK31 Decoder, Part 1 | SDR Adventure
Thenks, I’ll look into it later.
I experimented with an encoder here:
PSK31 GNU Radio Simple Transmitter - YouTube
Yes, I saw that.
It would be allot more work writing the GUI front end than the actual
GR portion of the modem; probably why it has not been done.
My initial thought is that I feed the decoded bits to a TCP sink, and I
write
a GUI in C, that listens on that particular TCP port. Unix socket would
be
nicer, but I can’t find a unix domain socket sink/source.
Is there any other way to get data and feed to other C application?
73! de HA5OGL
–
Levente Kovacs
CTO, CSO
ZeroMQ has just been implemented in GR:
If you check out the latest GR from Github you’ll see the blocks in GRC.
I
have not tried it. Here is more info:
http://gnuradio.org/redmine/versions/42
I was playing around with receiving data from the GR flow into Python
via
message queues. They do work, and I was able to empty the queues more
than
fast enough for 31 bps. However I have read the functionality will be
deprecated. There is a good write up here:
http://ha5kfu.sch.bme.hu/fft_test
and here:
Thanks,
Lou
KD4HSO
Levente Kovacs wrote
–
Levente Kovacs
CTO, CSO
http://levente.logonex.eu
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Regarding doing it in C; everything seems to be mostly there to do it in
Python as a native GR application.
-
A QT-GUI text input box would be needed to buffer-up the transmit
text as
it is typed, convert to varicode then drop the bytes into the transmit
stream, interrupting the continuous 01010101… The modulation is
simple.
-
The RX signal processing may be able to use the PSK receiver, then a
custom block would have to be written for the varidecoder, maybe dumping
the
text as messages, or to stdout.
-
The latest QT frequency sink has a click to tune functionality,
generating a frequency message, and the frequency translating FIR filter
has
a tuning message input. What I don’t know is if the PSK receiver has
wide
enough carrier recovery for point-and-click tuning, given 31 bps and a 2
kHz
channel bandwidth. I suppose some experimentation is in order.
Anyway, I think 50% of it is there already to do it all in GR.
Thanks,
Lou
KD4HSO
Levente Kovacs wrote
My initial thought is that I feed the decoded bits to a TCP sink, and I
write
a GUI in C, that listens on that particular TCP port. Unix socket would be
nicer, but I can’t find a unix domain socket sink/source.
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