[AMPS]n4kw@citrus.infi.net RJ-iA relay contact-life on CW?

[Dick Green]

>Unfortunatley, the FT-990 does not activate the T/R line until 7.5ms after
>key closure, leaving only 2.5ms for the amp's relay to close!

€  does the amplifier control signal pass through a relay in the 990?

Ooops. I should have been more clear about this. I didn't measure relay
closure time on any of the rigs. I timed only the solid-state T/R signals
available on the back panels of all three rigs. The 950 has a signal that
goes to +12V on transmit. Back when I had a 950, I used to feed that signal
through a bipolar transistor circuit to key the amp (I used Rich's circuit
design for that.) The FT-990 and the FT-1000mp both have back panel pins
that are grounded by a transistor on transmit (when the noisy internal
linear relay is disabled.) These pins can be connected directly to amps
using low voltage keying signals. The 990 manual says the transistor
(2SD669A) can handle up to 50V @ 500ma, while the 1000mp manual says the
transistor (2SC3444-T11-E) can handle 15V @ 100ma.

The Yaesu rigs also have a "Transmit Inhibit" (TX INH) pin on the same
connector. When a connector is plugged into the jack, the rig won't put out
RF until this pin is grounded. In  theory, you can key the rig, have the
rig's T/R line key the amp, then have the amp's T/R sequencer ground the TX
INH pin on the rig. Due to the error in T/R line timing in the FT-990, this
doesn't work very well -- the CW waveform still gets severely clipped due to
the long delay between key closure and T/R activation. It works better to
key the amp directly with an external keyer, then use the amp's T/R
sequencer to key the rig. This prevents hot switching and the external keyer
can be adjusted to add enough weight to counter the clipping. Unfortunately,
then you can't use the 990's built-in keyer.

73, Dick WC1M



--
FAQ on WWW:               http://www.contesting.com/ampfaq.html
Submissions:              amps@contesting.com
Administrative requests:  amps-REQUEST@contesting.com
Problems:                 owner-amps@contesting.com
Search:                   http://www.contesting.com/km9p/search.htm