AMRAD at Mason-Dixon Hamfest Oct 24, 2010

[Frank Gentges]

  Tacoistas,

We had a good Charleston building session yesterday, August 24th.  Each 
person built their own and the success rate was much better than the 
last time when we tried to build multiple receivers at a time.  We still 
have a number of people that are on our list as wanting to build a 
receiver but have not yet had a chance to do it.

Here is your chance to get some experience building an SDR receiver and 
some experience building surface mount technology.  At AMRAD we have 
learned how to deal with surface mount in your home and this is your 
chance to learn from our experience.

We have been talking with the people at the Carroll County Amateur Radio 
Club about doing a Charleston receiver build session somewhere in the 
Westminster area.  What we have worked out is to have a Charleston build 
session at the Mason-Dixon Hamfest on October 24th, 2010.

They have a large room where they have held lectures in the past and the 
plan is for AMRAD to use that room to build receivers and to have some 
talks and demonstrations alongside the hamfest.

We will bring some our specialized gear for building these surface mount 
receivers.  We have PC boards and the needed parts to make up complete 
receivers.  We will prepare the bare boards using our stencil setup to  
put the solder paste onto the solder pads on the PC board.

Once the board has the solder paste in place, the builder will take 
their board to a workstation with a bright light, a magnifying glass or 
stereo microscope, tweezers etc.  The builder will use an assembly 
manual which shows where each part is placed.  After going through all 
the parts and all the pages of the manual, the board will then go to the 
reflow soldering workstation.

We have adapted a toaster oven with a temperature controller and 
computer.  This automates the heating and cool down of the board to 
reflow the solder paste along the time and temperature profile that is 
optimum for soldering the parts to the board.  The setup worked great 
yesterday and produced the best looking and working soldering so far we 
have experienced.

After this, the builder will then go to a soldering iron workstation to 
solder the connectors and a couple of large components to their board.  
After this, the board will be tested first for power up and current 
draw.  Once this checks out, the receiver will be connected up to a 
Digilent Nexsys II development board and computer to check out its 
operation with a simple spectrum analyzer program.  Once this checks 
out, the builder goes home with a working Charleston SDR receiver.

The cost to the builder for the receiver is $100 which is our cost for 
the parts.  It is a great experience with building a device using 
surface mount technology.  The receiver works with an FPGA development 
board.  The software for this is free and down-loadable from the Xilinx 
web site.   Go to the AMRAD web site for more information on the 
Charleston receiver project.  It is at

http://amrad.org/projects/dsp/

You can download a CD image with a lot of information there.  The file 
is in iso format and is

http://amrad.org/projects/dsp/CharlestonQSV2.iso

The file is several hundred megabytes so you will need to be prepared to 
wait for the download.

Frank K0BRA