[Discuss-gnuradio] BPSK31 Adventures

[Iain Young, G7III]

Hi Folks,

Inspired by Javier and Martin's recent posts on DPSK, I thought I would
resurrect my (Amateur Radio )(B) PSK31 transceiver implemented in GRC.

I can use the MPSK receiver block in GRC to successfully decode anything
up to BPSK500 - I'm sure I could go higher, but fldigi only transmits up
to 500, and I was using that as a known good transmitter.

Knowing that in the future I would want DBPSK (for some satellite work),
and transmit capability (I could not find a MPSK Transmitter block), I
started to think about using the PSK Demod block in GRC instead.

I set the number of constellation points to 2 (for BPSK), set the
differential encoding to "No", and set the samples/symbol to the
equivalent value in the MPSK Receiver block.

There I come across a problem. What to set Excess BW, Frequency BW,
Timing BW, and Grey code to. I have looked at Tom's page on the
Frequency BW, but am afraid I don't grok that side of things at all
well.

Is there a way to work out what those value should be from the working
values of the MPSK Receiver block ?

Attached is a flowgraph (both .png and .grc) Both the MPSK Receiver
chain, and the PSK Demod chain eventually output to a file sink for
doing the varicode decoding.


Two quick further questions on the PSK Demod block (which actually
uses the Gerneric Demod block to do most of the dirty work):

1) Can someone confirm if I need to use the packed to unpacked block
that I'm using ? I've seen notes that the output is indeed packed (hence
the unpacker being in the flowgraph), but also other places saying it's
already unpacked ? Or is it just the DxPSK block that has the unpacked
output ?

2) Do I need to use AGC before it ? Again I came across some places
that say it's already in there, but couldn't see any evidence. Is it
just the DxPSK block that incorporates the AGC block ?


All the Best

Iain

multi_PSK_Decoders.png
Description: PNG image

multi_PSK_Decoders.grc
Description: Text Data