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[aprssig] NWS CAE

Wes Johnston, AI4PX wes at ai4px.com
Sat Sep 22 22:26:58 UTC 2007

Well, we attended a meeting at the NWS office in Columbia SC today.  They
have a PC running VMWare which allows them to run xastir under windows along
with AGWPE sound card software.  The PC has two sound cards, and that's 4
channels of audio.  What to do with 4 channels of audio?  Monitor 4 voice
repeaters for mic-e packets of course.  They have three 2m only mobile rigs
and a tm-d700.  We set it up so that 1/2 of the D700 is data on 144.39, and
the other 1/2 is monitoring a 70cm voice repeater.  The data 1/2 of the d700
is connected to the PC with a serial cable.

Here's where it gets good.  W4CWG has made a REALLY nice audio mixer for
them.  This mixer allows a pass thru for the 4 audio lines from the radio
speakers thru to the line level inputs via audio transformers (a la psk31
interface).  The speaker outputs are paired so that each one goes to the tip
or ring of a stereo 1/8" jack, which in turn plugs into the line input on
the PC's sound cards.  This is a 4 mono into 2 stereo arrangement.

The 4 channels of audio are available individually via headphone jacks on
the front of the box, but they also feed two 4 channel mixer busses (bus a
and bus b).  You can mix audio from any of the 4 sources into bus A and/or
bus B, and there are head phone jacks for each bus.  Additionally, there is
a headphone jack for both busses and a speaker jack around back.  All of
this allows any combination of 1 thru 4 operators present to mix-match
listening to audio from any combination of the 4 radios.  With headphones on
each operator, they can all work in close proximity to each other.  Ohh and
there are also LEDs on top of each column in the mixer to let us see which
radio has active audio.

W4CWG has said he'll provide a PDF with a schematic in it to me by email.
When I get it I'll post on a web site somewhere.

They also have mounted a big screen LCD over the ham station that the
meteorologists can control to allow us to see their nice sat images and
radar. With xastir, we can also overlay the ridge radar over the positions
of spotters running aprs (or spotters that we have created and plotted on
the map ourselves).   We will also be able to put our xastir image on the
big LCD for the meteorologists to see.  There is also a printer on the ham
table so if a weather warning is issued, we can see it right away when
running the skywarn net.

Thanks to Gale, KC4PL for creating the VMware image that they use (it's bomb
proof since if they screw it up, they can simply copy the VMware file back
from the DVD).

And thanks to Steve K9NWS for seeing this project thru...


In theory there is no difference between practice and theory.
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