Here is the way I do QSK with my FT-1000MP which is basically the same set
up as the 990 as far as qsk is concerned.
I have an Ameritron AL-80b which has an output of up to 900 watts.
In 1974, I built an Electronic TR switch from plans in the ARRL handbook.
It consists of nothing more than a 12AU7 tube, a coil,switch, variable
capacitor and a simple dc power supply. There are 3 coax jacks on the
back.
To connect this, you run the transceiver's main antenna input into the
amplifier's antenna input as you normally would. Run the amplifiers output
into and back out of the TR switch. Inside the tr switch, we simply tap
off the center conductor of the coax, run this through the tube then to
the 3rd coax jack on the tr switch which goes to the receiver input of
your transceiver.
As you can see, there is NO switching of the RF involved here at all. No
worrys of hot switching or dot clipping. The TR switch provides another
stage of RF for the receiver too. Keep all leads as short as possible.
When the amplifier is turned off, simply hit the antenna switch on the
transceiver to change the rx back to the main antenna input.
In the past, TR switches were known to cause TVI but with cable tv, there
is little to be concerned with. It's a great system. E-mail me if you have
any questions.
Steve Ellington N4LQ@IGLOU.COM Louisville, Ky
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