[aprssig] Re: GPS/PC/D7A

Stephen H. Smith wa8lmf2 at aol.com
Thu Feb 22 03:16:31 CST 2007

jasonacg @ citicom.com wrote:
> Stephen H. Smith wrote:
>> However, there is a workaround.   Run UIview on the PC which will 
>> accept the data sent from the D700.   In turn, UIview has a feature 
>> to re-transmit the received GPS data, reformatted back to standard 
>> NMEA format, out a virtual COM port for use by a second program.    
>> In turn, you can use a software bridge driver to connect this virtual 
>> port to any NMEA-using application such as Street Atlas, MapPoint, 
>> Precision Mapping etc.   
> Okay, this may be the solution I was looking for. But the use of a 
> software bridge driver is "uncharted territory" for me. Would a 
> typical Windows installation have such a driver present, and if not, 
> where do I find instructions for download/install/config/use?
> In your workaround, is the D7[00] set to APRS mode or TNC mode?

You always set the TH-D7/D700 TNC mode to "PACKET" when external devices 
are being used.     In self-contained APRS mode, nothing gets echoed out 
the main serial port, although the serial port IS available for non-TNC 
related operations such as programming memory channels.

The serial port bridge is not part of Windows. It is a third-party 
supplied piece of software.

What version of Windows are you running?   For Windows 2K/XP, the serial 
port bridge for MixW works and is a free download.  This installable 
device driver is a free download,  and simulates a pair of serial ports 
cross-connected; i.e. a virtual null-modem. You set UIview's GPS output 
to use one of the virtual ports, and your mapping application's GPS 
input to use the other.  

You configure the driver in the Windows device manager to create up to 
10 pairs of cross-connected pairs of  simulated COM ports using any COM 
numbers NOT used by physical devices such as  actual serial ports. 
modems, IR links or USB-to-serial dongles.   Go to the page:
      < http://mixw.net/related.htm >    

Scroll about 1/3rd of the way down the page and look for "TNC 
Emulation".   The original intent of this driver is to allow the MixW 
multimode soundcard program to act like a virtual multimode data 
controller (i.e. PK232 or KAM) for use with external programs like 
Airmail, packet clusters, BBS systems, or even APRS apps that expect 
TNCs on serial com ports.   However the driver works independently of 
MixW.  It can connect ANY two programs together that would normally use 
serial ports to communicate when run on  the same PC.   

Once installed, you can test the bridge by starting TWO copies of 
Windows Hyperterminal on the same PC. Set one copy to use the COM number 
on one side of the bridge, and the other copy to use the port on the 
other side of the bridge.   You should then be able to type messages to 
yourself from one window to the other.

Some possible applications:

I have connected together a GPS simulator program (that would normally 
OUTPUT to a serial port) to various mapping programs (that would 
normally INPUT GPS data on a serial port).  

I have connected the output of MixW running in Packet mode to the serial 
(TNC) input of UIview . On HF 300 baud packet, the MixW soundcard soft 
TNC used with a good sound card seems to outperform any hardware TNC 
device I have ever used. 

I have bridged the regenerated GPS output of UIview to TopoUSA, 
MapPoint, Street Atlas, Streets & Trips and Precision Mapping.

The MixW bridge only works on Win2K and XP. If you have to do something 
similar with Win98, the GPSgate utiltiy from Franson software can do the 
same thing on any flavor of Windows.  Originally, this program was 
intended to take data from a physical serial port and deliver it to any 
number of virtual COM ports in order to share a single GPS with several 
programs at the same time.   The current version can also bridge a 
virtual COM port instead of a real one, to any number of additional 
virtual COM ports on the other side.   [This was originally so that the 
virtual COM port produced by USB-interfaced GPS receivers could be 
shared to multiple apps.]   I have used it quite successfully to share 
the regenerated GPS output from UIview with TopoUSA, Streets & Trips, 
and Precision Mapping all at the same time.  More details on this $15.00 
piece of shareware  at:

     < http://www.franson.com >  

One other consideration in using the regenerated GPS output from UIview:  

Normally the TNC init file for the D700 / TH-D7 sets these devices to 
echo GPS data to the PC once every 10 seconds.  The default behavior of 
NMEA GPS devices, which most programs expect, is to output new data once 
a second.  UIview  "fakes" this by sending the SAME data repeatedly once 
a second until new data arrives from the Kenwood, in order to keep 
external applications from thinking the GPS has failed when they don't 
get an update every second.  The default settings will result in rather 
slow and jerky updates on any mapping program using the UIview output. 

You can edit the D700 TNC init file in UIview to command the Kenwood to 
send GPS data much more frequently.   In UIview pull down "Settings, 
Comms Settings".  With the D700 tnc type, selected, click the "Edit" 
button to alter the init file.  Look for the string "LTMON 10".  This 
string determines the number of seconds between GPS updates.  If you 
have a typical modern fast PC (i.e. over 800 MHz or so), you can set 
this down to "LTMON 2" or "LTMON 3" and vastly increase the position 
update rate your external apps see. 

Since you are using a radio-to-PC serial port baud rate of 9600 while 
data is coming in over the air at only 1200 baud, even a far higher GPS 
reporting rate won't conflict with your ability to receive off-air data 


Stephen H. Smith    wa8lmf (at) aol.com
EchoLink Node:      14400    [Think bottom of the 2M band]
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