[CQ-Contest] FT990 CAT Problem Solved

[Joe Subich, W4TV]

Tom,

Yaesu radios including the FT-990, FT-1000D with TTL CAT ports use an 
emitter follower with a high impedance as driver on the SO (serial out)
line.  This is no problem when driving Yaesu's FIF-232C which uses an 
optical isolator.  However, when driving a TTL or CMOS gate (7408, 
MAX-232, etc.) used in many of the home made TTL-RS232 converters, the 
emitter follower does not provide enough load to pull input of the 
buffer/converter low (< 0.5 volt) in the off state.  

Yaesu recognized the problem and added a 1.5K resistor from SO to 
ground in later production of the FT-990, FT-1000D and other radios 
using a similar circuit.  In practice any resistor between 1 K and 
4.7K will probably work.    

There is a  very quick way to determine if your Yeasu is effected ... 
turn off the radio and measure resistance from pin 2 (SO) and pin 1 
(ground) of the CAT jack.  If you measure less than 5 K Ohms, you 
should add a 1.5 K or 2.2 K resistor inside the radio (first choice) 
or to the interface (second choice). 

By the way, all microHAM interfaces include a proper "pull down" to 
work with both early and late Yaesu radios.  

73, 

   ... Joe, W4TV 
    



> -----Original Message-----
> From: cq-contest-bounces at contesting.com 
> [mailto:cq-contest-bounces at contesting.com] On Behalf Of Tom Moore
> Sent: Saturday, July 29, 2006 2:52 PM
> To: cq-contest at contesting.com
> Subject: [CQ-Contest] FT990 CAT Problem Solved
> 
> 
> There was some earlier discussion/questions by me and others 
> about CAT problems with the FT990. (most discussion was on the 
> hamlogger32 email reflector and is sent here for info to any of 
> you who may have experienced this problem)
> 
> My wife's radio is an FT990 rv1.3 using a West Mountain Radio 
> RigBlaster Pro and Logger32
> 
> The problem was that the L32 software could talk to the radio 
> (i,e change freq etc) but L32 was not receiving anything from 
> the radio (i.e, frequency/mode display).
> 
> After trying all kinds of various settings and jumpers in the 
> Rigblaster, talking to Yaesu and West Mtn, looking at various 
> web sites and attempting various settings in L32, I finally 
> received the following:
>
> --------------------------------------------------
>
> Tom,
> 
> Issue looks like lack of data load on transceiver data output 
> line. FT-990 has a source driver data output which MUST be loaded 
> for proper operation.
> 
> Try this:
> 
> - Open DIN6 CAT plug
> - Pick a 1.5K ohm resistor and solder it between pin 1 (GND) 
> and pin 2 (SERIAL OUT)
> 
> GL
> 73 Jozef OM7ZZ
> ----------------------------------------------------------
> 
> Unfortunately, I could not find a 1.5K ohm resistor in my 
> junk box but I did find a 1.0K ohm resistor and hooked it up 
> as suggested by Josef. IT WORKS! 
> I have not tried it yet with Writelog or any other software.  
> Your mileage may vary. Many thanks to Jozef and all the others 
> who tried to help.
> 
> 73  Tom WX4TM
> 
>