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MFJ-1275 / MFJ-1279 Sound Card-to-Rig Interface Support

This document outlines two major problems that customers are having with the MFJ-1275 and MFJ-1279 Sound Card Radio Interface units.

I have an MFJ-1275/MFJ-1279 that seems to be stuck in transmit mode after Windows ME initializes. What is wrong?? It keeps my radio keyed up all of the time.

The problem is with Windows ME. It has been discovered that when Windows ME boots up it leaves the DTR (Data Terminal Ready) line of the serial port in a HIGH state. This is one of the serial port lines that controls the radio's PTT circuit when you want to transmit from his sound card software. This problem has been verified on Microsoft's website -- it is an inherent design flaw with Windows ME. The problem is described on the following Microsoft web page:

http://support.microsoft.com/default.aspx?scid=kb;EN-US;q285894

To download the hotfix, click here and follow the instructions in the text file.


I have an MFJ-1275/MFJ-1279 that seems to be stuck in transmit mode after Windows XP initalizes. What is wrong?? It keeps my radio keyed up all of the time.

It has been discovered that when Windows XP boots up it leave the DTR (Data Terminal Ready) line of the serial port in a HIGH state. This is one of the serial port lines that controls the radio's PTT cir cuit when the customer wants to transmit from his sound card software. This problem has been verified on Microsoft's website.

The fix for this problem is to go to the Device Manager within Windows XP and removing all of the Communication Ports, or COM ports, as listed under "Ports (COM & LPT)". After removing these ports from the Device Manager, re-boot Windows XP and it will re-install all of the drivers for these ports. This should fix the problem.




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