For those who don’t know, Git is a source code manager.  The purpose of it is to allow teams to work together on writing software, and let them edit the same files at the same time without a problem.  They also include tracking of what has changed in the files.

To make my life easier, I’ve also got the wordpress codebase in a separate directory. I started with version 2.5, so at the time I did:

cd /var/www
wget http://wordpress.org/latest.tar.gz
tar xzf latest.tar.gz
cd wordpress
git init
git add -a
git commit -a -m “Wordpress 2.5″

I then set a site up by doing:

mkdir /var/www/md1clv.com
cd /var/www/md1clv.com
git init
git pull ../wordpress

I follow the procedure for setting up a new Wordpress site, and then commit all the changes.

Today I noticed that Wordpress 2.5.1 had been released. Upgrading is pure simplicity - I just need to do:

cd /var/www/wordpress
rm -r *
cd ..
wget http://wordpress.org/latest.tar.gz
tar xzf latest.tar.gz
cd wordpress
# Check whether any new files have been added:
git status
# If so add them with “git add”
git commit -a -m “Wordpress 2.5.1″

Then for each site I just need to go into the site’s directory and run “git pull ../wordpress” then visit the upgrade.php page to complete the upgrade.

I love things that make my life simple!

(The next step to make things even simpler will be to find a Git repository of the Wordpress code, and pull from that instead of my own local wordpress directory.)

FDMDV takes a voice stream and puts it through a MELP codec, which gives a stream of 54 bit frames.  There are then 2 bits of text data added, and this 56 bit chunk is then split into 2 x 28 bit data frames, which are transmitted over 14 QPSK carriers, with a central BPSK carrier for tuning and framing indication.

I had been wanting to set up a compatible modulator/demodulator where it’s possible to easily change the modulation scheme (to add or remove carriers, and change from QPSK to other modulations) and voice codec used (to test the effects of codecs other than MELP.)

It’s pretty hard to get your head round how to map all of this into a GNURadio program - I’m using the GNU Radio Companion to help with this - but even so it’s a struggle.  I’ve simplified things by starting with just 4 carriers, but I’ve not managed to pass data across them yet.

If anyone has Been There Done That already, I would be really intrigued to hear how you accomplished it.  If anyone wants my work-in-progress flow graphs, then add a comment - otherwise I’ll put them up here once I’ve got something which works.

> Realizing the drawbacks of the “aliasing” using no filter it was sure
> a lot of fun jumping from 80M to 40M to 20M with just the DIP switch
> freq select. Of course “you” shouldn’t do this but I ended up using
> it this way for several days as my “main” receiver :))

My immediate thoughts on reading this are why not just send the output through a pair of analogue multiplexers like the 74HC4051.  This has <1dB loss at 30MHz.  The antenna would be connected to the common connection of the first multiplexer.  The 8 selectable lines would go to 8 different filters, which would then go into a second multiplexer.  The control lines of both muxes would be linked together, and connected to either the band selection switch or to outputs on the PIC.

I think I’ll have to order some of the v8.1 kits when they’re available

The reason for this became apparent when we put it into a power meter, and discovered that the most we could get out of it was 2W.  It seems like one of the two PA transistors isn’t doing a whole lot of amplifying.  Fortunately (and this is the reason I felt compelled to write about this kit) the circuit is reeeeheheheheeeealy easy to understand.  Dave Benson, NN1G, has done a lovely job with this design, which makes for very easy troubleshooting.  Okay, so I’ve not found the reason for the problem yet, but I’ve got a great idea about where to start looking.

If you’re looking for something to build for yourself in around half a day, this is a wonderful little kit.

GNU Radio should make it very easy to start playing with new modulation schemes and testing out ideas as quickly as we have them. Actually writing something non-trivial in GNU Radio can be a bit daunting though, especially for non Python programmers. Fortunately somebody has written a graphical interface (GNU Radio Companion, or GRC for short) which allows you to drag and drop processing blocks and be up and away with your idea in no time.

To see an example of the power of this, and how it makes designing radio systems easier, install GNURadio and GRC. Load up the

I must admit, I’m pretty disappointed with the state of software defined radio in the amateur world. We have great hardware available to us - USRP, FlexRADIO, HPSDR, Softrock and soon hopefully uWSDR - and decent software, but there doesn’t really seem to be any sign of people doing anything new.

GNU Radio should make it very easy to start playing with new modulation schemes and testing out ideas as quickly as we have them. Actually writing something non-trivial in GNU Radio can be a bit daunting though, especially for non Python programmers. Fortunately somebody has written a graphical interface (GNU Radio Companion, or GRC for short) which allows you to drag and drop processing blocks and be up and away with your idea in no time.

To see an example of the power of this, and how it makes designing radio systems easier, install GNURadio and GRC. Load up the

I must admit, I’m pretty disappointed with the state of software defined radio in the amateur world. We have great hardware available to us - USRP, FlexRADIO, HPSDR, Softrock and soon hopefully uWSDR - and decent software, but there doesn’t really seem to be any sign of people doing anything new.

GNU Radio should make it very easy to start playing with new modulation schemes and testing out ideas as quickly as we have them. Actually writing something non-trivial in GNU Radio can be a bit daunting though, especially for non Python programmers. Fortunately somebody has written a graphical interface (GNU Radio Companion, or GRC for short) which allows you to drag and drop processing blocks and be up and away with your idea in no time.

To see an example of the power of this, and how it makes designing radio systems easier, install GNURadio and GRC. Load up the

I must admit, I’m pretty disappointed with the state of software defined radio in the amateur world. We have great hardware available to us - USRP, FlexRADIO, HPSDR, Softrock and soon hopefully uWSDR - and decent software, but there doesn’t really seem to be any sign of people doing anything new.

GNU Radio should make it very easy to start playing with new modulation schemes and testing out ideas as quickly as we have them. Actually writing something non-trivial in GNU Radio can be a bit daunting though, especially for non Python programmers. Fortunately somebody has written a graphical interface (GNU Radio Companion, or GRC for short) which allows you to drag and drop processing blocks and be up and away with your idea in no time.

To see an example of the power of this, and how it makes designing radio systems easier, install GNURadio and GRC. Load up the

I must admit, I’m pretty disappointed with the state of software defined radio in the amateur world. We have great hardware available to us - USRP, FlexRADIO, HPSDR, Softrock and soon hopefully uWSDR - and decent software, but there doesn’t really seem to be any sign of people doing anything new.

GNU Radio should make it very easy to start playing with new modulation schemes and testing out ideas as quickly as we have them. Actually writing something non-trivial in GNU Radio can be a bit daunting though, especially for non Python programmers. Fortunately somebody has written a graphical interface (GNU Radio Companion, or GRC for short) which allows you to drag and drop processing blocks and be up and away with your idea in no time.

To see an example of the power of this, and how it makes designing radio systems easier, install GNURadio and GRC. Load up the packet_mod_demod.grc.xml file. This has a signal source being GMSK modulated and demodulated, with the input and output displayed on scopes.

In real systems, though, there is a certain level of noise which the receivers have to tolerate. We can see the effects of noise by creating a complex noise source, and then putting in an “add” operator to sum the signal coming from the GMSK encoder and the noise. Create another variable to control the amplitude of the noise, and in seconds you can be raising and lowering the noise floor and seeing the effect which that has on the received signal. I found with GMSK that the signal at the receiving scope was unusable above an SNR of about 0.18. Changing the GMSK coding to BPSK takes a minute, and lets you very quickly see how much more tolerent of noise BPSK is than GMSK