Tuesday Night Tech Net

[Nan and Sandy Sanders]

 From Hal WB3KDU

Tuesday Night Tech Net meets at 8 PM Tuesday on echo link and may 
link to the AMRAD repeater.
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Its been a busy week.  Frank G has signed up to produce a new ARRL 
publication on LF,
the new amateur bands.  There so much to write about both old technology and
brand new stuff like SDR.

I've gotten about ten emails from people asking to be put on the LF 
Experimental Part 5
license.   I'll have something of a roster going by next week and 
from there on to the FCC
paper work for the actual license.

On page 53 of the latest QST (july) is the RadWav/SkyPi-40 
transmitter.  This is a transmitter
that keys one of the output ports of a Raspberry PI to produce an RF 
carrier. Included are
the Raspberry PI board and a amp/filter board.  There are different 
programs to do
various modes like CW, RTTY and WSPR.   Some of you probably remember that
I put together a raspberry PI that transmitted FM on the FM broadcast band and
demo'ed it by play the orchestra version of the Star Trek theme 
through it.  We got
a number of spectrum shots of the FM signal and it was dirty all 
right!.   It produced
FM by keying a pulse width modulated waveform to create a  synthetic 
kind of FM.
The RadWAVE SKyPi-40 is something similar on 40-meters but they claim
to have cleaned up the signal a bunch and combined with the filter board
and amplifier the signal meets ham standards.  The idea here is can
we get this to work on 138khz or 480khz?  I might write a note to the 
manufacture
asking if they considered this.


March/April QEX has the beginning of a good article on SDR called 
"Hands on SDR."
They are walking through how BeMicroSDK which is based on an Altera FPGA.  The
FPGA is programmed in Verilog (its not too hard to learn) and the 
code is accessible.
The article discusses each of the SDR blocks code which is a good way 
to learn this
stuff.  In fact, these SDR are no where as complicated as a 
conventional double
conversion super-het, and whats amazing is that even with the pretty simple
block diagram the performance is competitive.  Its also fun to see a 
few equations
replacing some hardware like an AM demodulator that just computes the
square root of the sum of the squares of the I and Q lines.   This article is
good if you want to know whats "under the hood," of an SDR and were afraid
to ask.

----
There's been some unnecessary drama at AMRAD this week and I truly hope
responsible people can get beyond it.

Tech net is dedicated to networking those people interested in
experimenting, building and discussing ideas about new communications 
technologies and is open
to ALL persons interesting in contributing.

The opening of the two new LF bands  gives us a rare opportunity to experience
a new band in an unfamiliar frequency range with new problems to be 
overcome. This
will be exciting!

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Tue Night Tech Net meets at 8 PM Tuesday on Echo Link and may link 
the AMRAD repeater.
Sandy WB5MMB is Echo Link Conference Point Coordinator and net control.