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@contesting.com
> [mailto:cq-contest-bounces@contesting.com] On Behalf Of Tom Moore
> Sent: Saturday, July 29, 2006 2:52 PM
> To: cq-contest@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
>
>
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