Tuesday, April 22, 2008

FT-2000 FSK connection

Last week, I connected the FT-2000 with my homebrew interface, which use the opto coupler 4N32, for RTTY FSK keying. Calling CQ for quite some time without any reply and finally find out thatI wasn't getting any shift.

I've used this interface on other radios over the years with no problem, including FT-920, IC756pro and FT-990. Finally I solved the problem, by the help / information from one of the member in the FT-2000 newsgroup .

The 4N32 opto coupler has a 0.50 volt plus collector "on" voltage which is OK under the usual TTL "low" state and has keyed all my other radios with no problem.

The FT-2000 requires the low or "ON" state to be less than 0.4 volts in order to key the FSK line.

I replaced the 4N32 by a 4N37, which has 0.3 saturated voltage (VCE sat) and it works perfect now.

I believe the FT-2000 is the first of the Yaesu radios that makes extensive use of 3.3 volt (low power) CMOS logic. The "low" requirements of the low power CMOS devices is considerably less than the old CMOS and TTL (most of which worked below about .65 volts). The standard for low power CMOS is down around .3 volts