# BPSK31 Adventures **URL:** \ **Category:** GNU Radio\ **Created:** [July 15, 2012, 9:15pm UTC](https://www.ruby-forum.com/t/bpsk31-adventures/221447 "2012-07-15T21:15:38Z")\ **Posts on this page:** 2\ **Page:** 1
**Author:** ![aris](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/258eb7/32.png) [@aris](https://www.ruby-forum.com/u/aris)\ **Post date:** [July 15, 2012, 9:15pm UTC](https://www.ruby-forum.com/t/bpsk31-adventures/221447/1 "2012-07-15T21:15:38Z")
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 ---
**Author:** ![Iain\_YoungS\_G7III](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/i/3da27b/32.png) [@Iain\_YoungS\_G7III](https://www.ruby-forum.com/u/Iain_YoungS_G7III)\ **Post date:** [July 16, 2012, 9:39am UTC](https://www.ruby-forum.com/t/bpsk31-adventures/221447/2 "2012-07-16T09:39:24Z")
Hi Iain, On Sun, Jul 15, 2012 at 08:13:13PM +0100, Iain Young, G7III wrote: > Inspired by Javier and Martin’s recent posts on DPSK, I thought I would > resurrect my (Amateur Radio )(B) PSK31 transceiver implemented in GRC. Nice! > 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. Grey code doesn’t matter for BPSK, so ignore that. The frequency and timing loop BW’s depend on how quickly you want to acquire freq/timing synch, but don’t worry about these, either–if you don’t know what they exactly do, just use the defaults (I think something around 2\pi/100?) and play around with these values. The ‘excess BW’ is the rolloff factor of the root-raised cosine filter. > Is there a way to work out what those value should be from the working > values of the MPSK Receiver block ? It depends on your app. > 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 ? PSK Demod packs all bits of 1 sym per byte. As you’re using BPSK, you don’t need to unpack. You’ll have 1 bit per byte. > 1. 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 ? It’s not in there, but for PSK31, you might not need it, as all the info is in the phase anyway. MB – Karlsruhe Institute of Technology (KIT) Communications Engineering Lab (CEL) Dipl.-Ing. Martin B. Research Associate Kaiserstraße 12 Building 05.01 76131 Karlsruhe Phone: +49 721 608-43790 Fax: +49 721 608-46071 www.cel.kit.edu KIT – University of the State of Baden-Württemberg and National Laboratory of the Helmholtz Association