[aprssig] Re: VOX to key up soundmodem?

Stephen H. Smith wa8lmf2 at aol.com
Wed Apr 13 18:29:59 EDT 2005

scott at opentrac.org wrote:

>>yeah but, a TNC-X goes for $45.  The only reason I would want to do
>>sound card is to do packet on the cheap.
>Well, the real power in soundcard-based modes is flexibility.  You can run
>all sorts of different modes with the same hardware.
>I just can't believe how expensive these Rigblasters and things are. $105
>for the standard model?  For some audio isolation and connectors in a pretty
>box?  $290 for the 'pro' model.

And completely worthless since they DON'T provide  ground loop isolation 
between the computer ground system and the radio ground system. [The 
main reason for a "soundcard interface" instead of just using patch 
cords.]  RigBlasters transfomer-isolate the TX audio, and then 
completely defeat this by having a hardwired common ground return 
between the radio and computer by virtue of using an open-collector 
transistor instead of an opto-isolator or relay for PTT!

>For that price, I'd expect a peripheral that actually contained a USB
>soundcard chipset of its own, and drivers to avoid having to use the PC's
>existing serial ports.
There is such a device!  

The MixW "RigExpert" is a cigarette-pack-sized external USB-interfaced 
device that includes essentially a soundcard AND a serial port AND 
various single bit outputs for PTT, FSK keying and CW keying.  It 
operates directly with the MixW multimode soundcard software to provide 
both PTT/CW/FSK and CAT (Computer Aided Tuning) radio frequency and mode 
control/logging.  (Normally this requires TWO serial ports - one for the 
bit-fiddled handshaking lines for PTT/CW/FSK and a second one for the 
CAT control data stream.)   An additional driver makes it look like a 
normal WDM soundcard for other non-Mix soundcard apps.   And the whole 
thing is self-powered via the USB port. 

Info at:

Stephen H. Smith             wa8lmf (at) aol.com
Home Page:                   http://wa8lmf.com

New/Updated "Rev G" APRS     http://webs.lanset.com/wa8lmf/aprs
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