Radio Stuck in Transmit Mode

Serial Port Problem - DTR High
Common to Many Computers

Some new computers have BIOS that is equipped with what is referred to as Serial Plug-n-Play technology, which is their interpretation of an industry suggested method of discovering the identity of a device plugged into a serial port.Unfortunately some computer manufacturers did not correctly implement this technology and therefore it impacts connecting any device that use the DTR and/or RTS line of the serial port.Most Amateur Radio software falls into this category and regardless of what Radio to Computer interface you use, RIGblaster, Rascal, MFJ, Homebrew etc., if you have a computer with this issue, you WILL have this problem.

Unfortunately most computer Technical Support has turned a deaf ear to admitting this is their problem.But the fact remains NOT all computers have this issue (IBM, HP, Compaq) just to mention a few.

West Mountain Radio suggests to our customers, who own a computer with this issue, that they call Tech Support.We have tried, many of our customers have tried, but as of yet, we have not heard of anyone successful at getting a fix for this problem.

West Mountain Radio has been recommending the Ham Radio community in general boycott computers known to have this issue until they fix.

Several customers we have spoken with have reported they have been successful in solving this issue by downloading and installing the latest BIOS upgrade for their particular computer from the support site.However they also reported the writeup on the support site that accompanied these BIOS upgrades did not mention that it fixed this Serial Port issue.We suggest you call Tech support or check on the web site to see if there is a BIOS upgrade for your computer.If you call and speak with a Tech Support representative, we suggest you do NOT mention that you are using this computer for Amateur Radio NOR that you are calling about a Serial Port Problem but simply ask if there is a BIOS upgrade for your particular computer.

There is an item posted to a WriteLog Bulletin Board that addresses this issue, but not specifically related to any computer. It can be viewed at On this site, reference is made to a Microsoft Knowledge Base item that can be viewed here

If you are interested in learning more about Serial Ports and the RS-232 standard please see

Also if you are interested in learning more about Serial Plug'n'Play please see PNPCOM.DOC a Microsoft published document describing this technology.


As an aid in determining if there might be a specific program that is bringing up DTR, Windows/XP and later versions of Windows can be set to do a Selective Startup using the "msconfig" utility.

Use the "Run" menu item (Start | Run) and run "msconfig".

On the General tab make note of the current boot selection then choose "Selective Startup" and click OK or whatever it takes to accept that choice then get out of msconfig.

Restart the computer and step thru each boot step until the RIGblaster keys. Then note which program or driver caused that to happen.

Continue just to be sure nothing else turns it off and back on.

Rerun MSCONFIG and set the boot configuration back the way it was and restart the computer.

Do whatever needs to be done to correct the cause you found. MSCONFIG could also possibly used to do this.