[NA-User] Two-Radio Setup for SSB?

k8cc k8cc@comcast.net
Sun, 31 Mar 2002 22:33:48 -0500


My TopTen "DX Doubler" box does the same thing.  I had not dug into the 
problem but what you describe is the culprit I suspected.

If you look at the DX Doubler schematic you'll find that the TopTen boys 
made a mistake in the design of an otherwise most excellent unit.  When 
K1EA originally designed the CW keying standard for logging programs, the 
emitter of the NPN keying transistor was connected to pin 1 of the LPT 
port.  This pin is normally high at bootup, and has to be asserted low by 
the logging program.  In this way, the state of pin 17 can't cause the 
radio to be keyed until the program wants it to.  This is important because 
it appears that the initial state of pin 17 is random between different 

When N6TR added PTT control to TRLog, he simply duplicated K1EA's keying 
circuit for the PTT output, except connected to pin 16.  The same 
considerations apply - the initial state of pin 16 at startup appears 
random so the emitter of the NPN PTT transistor is tied to pin 1.

The problem with the TopTen DX Doubler is that the emitters of these 
transistors are not tied to pin 1, but are tied to ground.  Therefore, when 
you start the computer you might get unintended PTT and/or CW keying until 
the logging program is started.

There are two ways to fix this:

1. Modify the hardware.  I've not taken my DX Doubler apart to see how hard 
this would be.  Unless the PCB pattern is really dense, it should not be 
hard to isolate the emitters of the keying and PTT  transistors and tie 
them to pin 1.

2. I can make a little utility program which can be called early in the 
AUTOEXEC.BAT file to assert the LPT bits into states which are *off*.  This 
is probably the easiest route for running DOS, but I don't know how it 
would turn out under Windows.



At 08:34 PM 3/31/02 -0600, Randy Farmer wrote:
>I'm looking for guidance on how to set up NA for two-radio use in SSB.
>Late last year I acquired one of the Top Ten "DX Doubler" SO2R boxes, a 
>product I can heartily recommend. I configured it as described in the 
>manual. It requires that the two radio control with antenna switching (not 
>with DVK) be configured in NA. I got things set up and it works perfectly 
>on CW.
>I fooled around in WPX SSB this weekend and discovered that for some 
>reason the computer insisted on asserting LPT Pin 16 high whether NA was 
>running or not. Whatever function that pin has is apparently supposed to 
>be logic high by default, at least on my logging computer. It does the 
>same thing in either DOS 6.2 or Win98.
>Since Pin 16 is used for PTT, the result was that every time I put the Top 
>Ten box TX control in the Auto position for computer control the PTT line 
>was pulled down and the selected radio went into transmit. I tried setting 
>up another dummy contest file for WPX CW; as soon as NA started up Pin 16 
>went low and stayed that way until it the CW keying was activated. 
>Re-opening my file from ARRL CW also resulted in proper operation. Both 
>the 10.54 and 10.55 versions of NA.EXE acted the same way.
>Have I missed something in the configuration, or is there a bug in the 
>program, or is it SUPPOSED to act that way and I'm just failing to 
>understand what's going on? I'd appreciate hearing from anyone who has set 
>up his station for full NA two-radio control to help sort this problem out.
>And regarding the beam heading operation, I too would like the headings to 
>be displayed in the mult window before the station is logged.
>Randy W8FN
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